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HP 6236B

1. 0180 1921 0180 1899 0150 0052 0160 0269 0180 0376 0180 0218 0160 2012 0180 1888 0160 4065 1901 0327 1901 0033 1901 0327 1901 0033 1901 0327 1901 0416 1901 0033 1901 0460 1901 0033 1901 0327 1901 0416 1901 0327 1901 0327 1901 0460 1901 0327 Table 6 4 Replaceable Parts Continued DESCRIPTION Diode Si Inductor ferrite bead Q2 O3 CR49 SS NPN Si SS PNP Si Power PNP Si SS NPN Si SS PNP Si SS NPN Si SS NPN Si var fxd fxd fxd var fxd fxd fxd fxd fxd fxd fxd fxd fxd fxd var fxd fxd fxd fxd fxd var 10k VOLTAGE 20V film 2 61k 1 1 8W ww 0 1 10 3W comp 18 5 1 2W ww 3k ww 1 25 1 2 5W film 5 49k 1 1 8W film 1 5k 1 1 8W film 110k 1 1 8W film 139 1 1 8W comp 15k 5 1 2W comp 510 5 1W comp 10k 5 1 2W ww 0 25 10 3W comp 18 5 1 2W ww 3k ww 1 25 1 2 5W film 139 1 1 8W film 15k 1 1 8W comp 510 5 1 2W comp 10k 5 1 2W 10k VOLTAGE 6V or 18V fxd fxd fxd fxd film 8 66k 1 1 8W film 2 87k 1 1 8W ww 0 1 10 3W comp 18 5 1 2W Not used fxd var fxd film 2k 1 1 8W ww 3k film 23k 1 1 8W Not used fxd fxd fxd ww 0 25 1 2 5W ww 0 625 1 2 5W film 750 1 1 8W Not used D M h OG GAMM HN MFR PART NO MFR CODE 1N485B 56 590 65 4A6 551147 Note1 2N2904A 2N3740 551147 Note 1 2N4036 2N2714A 551147 Note 1 43X Type MF4C T 9 RS
2. 0686 1155 0698 4470 0811 1816 3101 1914 06236 80091 1826 0092 1820 0223 1902 1221 1902 3149 1902 0650 1810 0217 Table 6 4 Replaceable Parts Continued DESCRIPTION Front Panel Electrical Indicator light LINE ON Voltmeter 25 Voltmeter 0 25V Ammeter 0 3A Ammeter 0 1 2 Toggle Switch LINE ON 3 pos rotary switch METER var 10k TRACKING RATIO Rear Heatsink Electrical Fuse 2A 250V Std Option and Option 100 Fuse 1 A 250V Options 220 and 240 Power PNP Si Power NPN Si Circuit Board Mechanical Heat Dissipator CR51 52 Q2 Q11 in 6236B Q2 in 6237B Heat Sink Q11 Spacer for Q11 heatsink Rubber bumper Front Panel Mechanical Binding Post red Binding Post black Meter bezel Spring compression meter mount Retainer push on for DSI Knob R1 R41 R77 S2 Miscellaneous Bushing transistor insulator Transistor insulator mica Fuse holder Lockwasher fuseholder Nut nylon 1 2 24 Foot rubber Line cord strain relief Line cord Chassis assembly left Chassis assembly right Front panel 6236B Front panel 6237B Heat sink rear Cover top and bottom Packing carton Floater pad packing carton MFR MFR Ta PART NO CODE 7318 PHI 312002 312001 J1528 2N3055 Note 1 342014 H A bh Note 1 Alternate part number See para 5 43 6 6 HP PART NO 1450 0566 1120 1380 1120 138
3. ADDRESS CODE MANUFACTURER ADDRESS Allen Bradley Co Newton MA Ferroxcube Corp Saugerties NY Electra Midland Corp Mineral Wells TX Clarostat Mfg Co Inc Dover NH National Semiconductor Radio Corp of America Solid State and Corp Receiving Tube Div Somerville NJ Hewlett Packard Co G E Semiconductor Union Carbide Corp Products Dept CTS Corp Sprague Electric Co Electro Motive Mfg Co Inc Motorola Semiconductor Willimantic CT Prod Inc Philadelphia PA Milwaukee WI C amp Components Inc Santa Clara CA Palo Alto CA New York NY Syracuse NY Elkhart IN North Adams MA Phoenix AZ IRC Div of TRW Inc Dale Electronics Inc Wakefield Engr Inc Aktiebolaget Rifa Columbus NE Wakefield MA Bromma Sweden Littlefuse Inc DesPlaines IL IRC Div of TRW Inc Burlington IA 6 2 DESCRIPTION C1 C2 C3 4 C7 C8 9 C11 C12 C13 C14 C17 C18 19 C21 6236B 6237B C22 C23 C24 C27 6236B 6237B C28 29 6236B 6237B C30 6236B 6237B C31 6236B 6237B C32 C33 C34 CR1 CR2 7 CR9 11 12 21 CR22 26 CR28 29 31 32 CR41 CR42 43 CR44 CR45 47 CR49 CR51 52 CR53 54 6236B 6237B CR55 56 CR57 CR59 6236B 6237B Table 6 4 Replaceable Parts Printed Circuit Board Assy fxd fxd fxd fxd fxd fxd fxd fxd fxd fxd fxd fxd fxd fxd fxd fxd fxd fxd fxd elect 1804F 50V tant 6 8uF 35V polyester 220
4. Table 1 1 Specifications Models 6236B and 6237B Continued LOAD EFFECT TRANSIENT RECOVERY TIME All Outputs Less than 50usec for output recovery to within 15mV of nominal output voltage following a load change from full load to half load or vice versa OUTPUT VOLTAGEOVERSHOOT All Outputs During turn on or turn off of ac power output plus overshoot will not exceed 1 V if the output control is set for less than 1V If the control is set for 1V or higher there is no overshoot TEMPERATURE COEFFICIENT All Outputs Less than 0 02 plus 1 mV voltage change per degree Celsius over the operating range from O to 40 C after 30 minutes warm up OUTPUT IMPEDANCE typical O to 20V Output 0 5mQ plus 1 5uH to 20V Output 0 5mQ plus 1 5uH Model 6236B to 6V Output 0 3mQ plus 14H Model 6237B to 18V Output 0 3Q plus 1 5uH Operating characteristics listed as typical are provided for the user s information only and are not warranteed specifications METER ACCURACY 4 of full scale 1 3 RESOLUTION Minimum output voltage change obtainable using front panel voltage control to 20V Outputs 7OmV Model 6236B O to 6V Output 20mV Model 6237B O to 18V Output 70mV TEMPERATURE RATINGS Operating O to 40 C ambient At higher temperatures output current is derated linearly to 50 at 55 C maximum temperature Storage 40 C to 4 75 C METER RANGES O to 20V Output 0 25V 0 0 6A O
5. amp step change in load current where Y equals 15mV and Z is the specified load current change equal to half of the current rating of the supply The nominal output voltage is defined as the dc level halfway between the static output voltage before and after the imposed load change 5 30 Measurement Techniques Care must be taken in switching the load resistance on and off A hand operated switch in series with the load is not adequate since the re sulting one shot displays are difficult to observe on most oscilloscopes and the arc energy occurring during switching completely masks the display with a noise burst Transistor load switching devices are expensive if reasonably rapid load POWER SUPPLY OSCILLOSCOPE UNDER TEST CONTACT PROTECTION NETWORK NOTE3 i THIS DRAWING SHOWS A SUGGESTED METHOD OF BUILDING A LOAD SWITCH HOWE VER OTHER METHODS COULD BE USED SUCH AS A TRANSISTOR SWITCHING NETWORK MAXIMUM LOAD RATINGS OF LOAD SWITCH ARE 5 AMPS 500V 250W NOT 2500W USE MERCURY RELAY CLARE TYPE HGP 1002 OR W E TYPE 2768 SELECT CONTACT PRO TECTION NETWORK ACCORDING TO MERCURY RELAY MANUFACTURERS INSTRUCTIONS 4 EACH Ry IS EQUAL TO TWICE THE NORMAL FULL LOAD RESISTANCE Gap USED IN PREVIOUS TESTS LINE SWITCH REPETITIVE LOAD SWITCH NOTE 1 Figure 5 5 Load Transient Recovery Time Test Setup current changes are to be achieved Instead a mercury wetted relay should be used f
6. amps 6236B or 1 0 amp 6237B j Connect the DVM directly across the output terminals of the 6V 18V supply record the DVM reading and then open the switch in the 6V 18V load circuit without disturbing the supply s output terminals The DVM indication should not change by more than 2 6mV 6236B or 3 8mV 6237B k Check the rated output and ammeter accuracy of the 20V and 20V supplies similarly by connecting the test setup of Figure 5 3 to each output in turn For each 20V supply make the total resistance of RL and the current sampling resistor 40 ohms set the 20V VOLTAGE control for a current indication on the DVM of O 5A check that panel meter 5 3 indication is within 496 of O 5A connect the DVM to the fully loaded output terminals and compare the output voltage before and after the load circuit is opened The voltage should not change by more than 4mV While checking each supply the other two must be fully loaded Current Limit Disconnect all loads from the supply m Connect the test setup shown in Figure 5 3 to the 20 volt output Substitute a short for and leave the load circuit switch open n Set the voltage of the 20V supplies to 20 volts o Close the load switch and determine the current flow through the current sampling resistor meter shunt by measuring its voltage drop with the DVM The current should be 0 55A 5 p Check the current limit of the 20V supply in the same way Its short c
7. breaker jack jumper diode relay device signaling inductor lamp meter 6 1 Table 6 1 Reference Designators Continued plug transistor resistor switch transformer terminal block thermal switch vacuum tube neon bulb photocell etc zener diode socket integrated cir cuit or network Table 6 2 Description Abbreviations A ampere alternating current assy assembly bd board bkt bracket degree Centigrade cd card coef coefficient comp composition CRT cathode ray tube CT center tapped dc direct current DPDT double pole double throw DPST double pole single throw elect electrolytic encap encapsulated F farad OF degree Farenheit fxd fixed Ge germanium H Henry Hz Hertz integrated circuit inside diameter incandescent kilo 103 milli 10 3 mega 106 micro 10 6 metal manufacturer modular or modified mounting nano 10 9 normally closed normally open nickel plated ohm order by description outside diameter pico 1012 printed circuit potentiometer peak to peak parts per million peak reverse voltage rectifier root mean square silicon single pole double throw single pole single throw small signal slow blow tantalum titanium volt variable wirewound Watt Table 6 3 Code List of Manufacturers CODE MANUFACTURER
8. from one line voltage option to another the following three steps are necessary t FRONT OF SUPPLY Figure 3 2 line Voltage Selector Set for 120 Vac 1 After making certain that the line cord is discon nected from a source of power remove the top cover from the supply and set the two sections of the line voltage selector switch for the desired line voltage see Figure 3 2 2 Check the rating of the installed fuse and repla ce it with the correct value if necessary For options 100 or 120 use a normal time constant 2 amp fuse HP Part No 2110 0002 For Options 220 or 240 use a normal time constant 1 amp fuse HP Part No 2110 0001 3 Mark the instrument clearly with a tag or label indicating the correct line voltage to be used 3 6 OPERATION 3 7 This power supply can be operated individually or in parallel with another supply see paragraph 3 19 All output terminals are isolated from ground The 20V and 6V or 18V outputs use a single common output terminal This common COM terminal or anyone of the other output terminals may be grounded to the chassis at the front panel ground terminal in Figure 3 1 or all outputs may be left floating Loads can be connected separately between each of the O to 20V output terminals and the COM terminal or between the 20V and the 20V terminals for a O to 40V output 3 8 Tracking Ratio Control 3 9 With the TRACKING RATIO control in the FIXED position the voltage of th
9. the voltage comparison amplifier in control of the supply s output If the load resis tance is decreased the higher output current increases ER48 until the algebraic sum of ER4g and ER46 makes the current comparison amplifier s inverting input slightly more negative than the 305mV potential on its non inverting in put When this happens the output of this amplifier goes positive and forward biases CR45 Since the current through CR45 tends to reduce the output of the supply the output of the voltage comparison amplifier goes negative in oppo sition to this change and reverse biases CR46 to leave the current comparison amplifier in control of the output Now that the current comparison amplifier is in control and for as long as the overload remains the supply s output voltage and current vary so as to maintain this amplifier s differen tial input signal near zero volts This results in the output current limit characteristics shown in Figure 3 3 4 30 If we assume for example that the voltage control is set for 5 volts and the load resistance is slowly decreased the supply goes into current limit at about 2 47 amps Here is why it occurs at that value At a 5 volt supply output ER46 is 5 6 of 440mV or 367mV In order for the algebraic sum of ER46 and to go as far negative as 30bmV and drive the amplifier output positive ER4g must reach 672mV Once reaches this value the current comparison amplifier controls the se
10. to 20V Output O 25V 0 0 6A Model 6236B to 6V Output O 7V O 3A Model 6237B O to 18V Output O 21V 0 1 2A DIMENSIONS 3 47 in Hx 8 22 in W x 12 56 in D 88mm H x 209mm W x 319mm D WEIGHT 9 5 Ib 4 3kg SECTION Il INSTALLATION 2 1 INITIAL INSPECTION TOP VIEW 2 2 Before shipment this instrument was inspected and found to be free of mechanical and electrical defects As soon as the instrument is unpacked inspect for any damage that may have occurred transit Save all packing Dee WS RR SPS ide 1208 7 mml materials until the inspection is completed If damage is found file claim with carrier immediately The Hewlett Packard Sales and Service office should be notified as soon 0 875 22 2mm as possible EH X e 2 487 2 3 Mechanical Check 3468 2 4 This check should confirm that there are no broken Val k knobs or connectors that the cabinet and panel surfaces REAR VIEW SIDE VIEW are free of dents and scratches and that the meter is not scratched or cracked 2 5 Electrical Check Figure 2 1 Outline Diagram 2 6 The instrument should be checked against its elec trical specifications Section V includes an in cabinet per formance check to verify proper instrument operation oe 2 7 INSTALLATION DATA i BRACKET Panel 2 8 The instrument is shipped ready for bench z operation Before applying power to the inst
11. 0pF 200V elect 1450uF 45V cer ObuF 400V elect 1804F 50V tant 6 8uF 35V polyester O1uF 200V polyester 3300pF 200V elect 1450uF 45V cer O5uF 400V elect 1000uUF 12V elect 1804F 50V tant 6 8uF 35V cer OObuF 100V polyester O1uF 200V elect 5600uF 25V elect 3000uF 40V cer ObuF 400V Not used Not used fxd fxd fxd fxd fxd fxd cer O 1uF 500V tant O 47uF 35V elect O 15uF 35V mica 330pF 500V elect 490uF 85V paper O 1uF 250Vac Diode Si 1A 200V Diode Si Diode Si 1A 200V Diode Si Diode Si 1A 200V Diode Si 1 5A 200V Diode Si Diode stabistor 150mA 15V Diode Si Diode Si 1A 200V Diode Si 1 5A 200V Not used Diode Si 1A 200V Diode Si 1A 200V Diode stabistor 150mA 15V Diode Si 1A 200V MFR PART NO 672D047 150D685X9035B2 292P22292 PTS Type68D D39532 33C17A3 CDH 672D047 150D685X9035B2 292P10392 PTS 292P33292 PTS Type 68D D39532 33C17A3 CDH 627D046 672D047 150D685X9035B2 C023B101E502MS27 292P10392 PTS Type 32D D40018 32D5278 DOB 33C17A3 CDH 41C92B5 CDH 150D474X9035A2 T110A154KO35AS obd Type 68D D38618 PME271 M 610 1N5059 1N485B 1N5059 1N485B 1N5059 1N4999 1N485B STB523 1N485B 1N5059 1N4999 1N5059 1N5059 STB523 1N5059 6 3 HP PART NO 0180 0634 0180 0116 0160 0154 0180 1893 0150 0052 0180 0634 0180 0116 0160 0161 0160 0155 0180 1893 0150 0052 0180 0633 0180 0634 0180 0116 0160 2639 0160 0161
12. 2 1120 1381 1120 1383 3101 1694 3100 1943 2100 3656 2110 0002 2110 0001 1853 0063 1854 0563 1205 0033 5000 6025 0380 0004 0403 0086 1510 0091 1510 0107 4040 0571 1460 0720 0510 0123 0370 1099 0340 0168 0340 0174 1400 0084 2190 0054 2950 0131 0403 0088 0400 0013 see par 2 21 5060 7955 5060 7956 06236 00001 06237 00001 5020 8423 5000 9424 9211 2518 9220 1218 APPENDIX A MANUAL BACKDATING CHANGES To adapt this manual to Model 6236A or 6237A instruments make the changes indicated in the table below SERIAL NUMBERS MAKE CHANGES ALL 1507A 00141 thru 00350 14364 00101 thru 00127 ALL 15114 00101 thru 00170 CHANGE 1 Delete R76 R77 and all references to the variable tracking ratio feature CHANGE 2 Change potentiometers R1 and R41 to 10kO panel mounted type HP Part No 2100 1854 CHANGE 3 Delete ferrite bead L3 9170 0894 from the lead of diode CR49 A 1 SECTION VII CIRCUIT DIAGRAMS 7 1 COMPONENT LOCATION DIAGRAM 7 2 component location diagram for power supply Models 6236B and 6237B is given below The illustration shows the physical locations and reference designations of parts mounted on the printed circuit card Not all parts are used in both models P70 METER V CIRCUIT 1 D I 7 3 SCHEMATIC DIAGRAM 7 4 Figure 7 1 is a combined schematic diagram of the 6236B and 6237B The test points circled numbers shown on the schematic corre
13. 2 MANUAL CHANGES Models 6236B and 6237B Triple Output DC Power Supplies Manual HP Part No 5950 1782 Make all corrections in the manual according to errata below then check the following table for your power supply serial number and enter any listed change s in the manual Model 6236B Model 6237B SERIAL MAKE SERIAL MAKE CHANGES CHANGES 1706A Note 1 1 1735A 00301 up 1 1705A Note 1 1 1732A 00601 up 1 ERRATA The corrugated shipping carton for this model has been changed to HP Part No 9211 2570 Two 9220 2703 floater pads are used CHANGE 1 Change R34 to 470 ohms 1 2W HP Part No 0686 4715 Also add three new resistors R78 and R79 both 825 ohms 1 1 8W HP Part No 0757 0421 and R80 750 ohms 196 1 8W HP Part No 0757 0420 R78 R79 and R80 are connected from base to emitter of O1 O7 and O3 respectively and are located on the circuit board as follows R78 between Q2 and CR28 R79 near R55 and R80 between Q3 and C17 These changes prevent a turn off overshoot 9 8 77 Note 1 Change 1 applies to the following instruments from earlier production runs Model 6236B serial 1705A 00502 505 507 526 533 534 536 541 544 546 547 573 577 594 Model 6237B serial 1706A 00263 264 269 272 291 296 298 299
14. 2 which regulates the flow of turn off bias through O1 s base emitter circuit The algebraic sum of the nearly constant turn on bias through R14 and the variable turn off bias through Q2 controls the conduction of series regulator transistor O1 4 19 Current Limit Circuit In the 20 volt regulator the current comparison amplifier compares the voltage across current monitoring resistor R8 to the fixed voltage across part of current limit adjust potentiometer R6 The current limit adjustment is set so that the input voltage to the current comparison amplifier is negative in the normal operating region but becomes zero when the output current increases to 0 55 amps When the amplifier s input voltage reaches zero it takes control of the regulator output voltage and reduces it as necessary to keep the output current from exceeding 0 55 amps When the overload is removed the output of the current comparison amplifier goes negative reverse biasing CR5 and returning control to the voltage comparison amplifier 4 20 Turn On Turn Off Control When the power supply is turned on or off Q15 in the turn on control circuit with holds turn on bias from Q1 while the regulator bias voltages are too low This prevents an output voltage transient from occurring before the amplifiers are properly biased The output of the 6 2V reference supply is also temporarily held at a low voltage by Q14 which conducts to short that output 4 21 Circuit Protecti
15. 2B EB1805 Type 110 F4 RS5 Type MF4C T O Type MF4C T O Type MF4C T O Type CEA T O EB 1535 GB5115 EB1035 RS 2B EB1805 Type 110 F4 RS5 Type CEA T O Type MF4C T O EB5115 EB1035 43X Type MF4C T 9 Type MF4C 1 RS 2B EB1805 CEA993 Type 110 F4 Type MF4C T O RS5 RS5 Type MF4C T O Note 1 Alternate part number See para 5 43 HP PART NO 1901 0033 9170 0894 1854 0448 1853 0012 1853 0052 1854 0448 1853 0041 1854 0027 1854 0448 2100 3461 0698 0092 0811 1827 0686 1805 2100 1823 0811 3384 0698 3382 0757 0427 0757 0466 0698 4099 0686 1535 0689 5115 0686 1035 0811 1829 0686 1805 2100 1823 0811 3384 0698 4099 0757 0446 0686 5115 0686 1035 2100 3461 0698 8076 0698 7631 0811 1827 0686 1805 0757 0283 2100 1823 0698 3269 0811 3383 0811 3395 0757 0420 R50 6236B 6237B R51 R52 R53 R54 6236B 6237B R55 6236B 6237B R56 R57 R58 59 R60 R61 R62 R63 R64 R65 R66 R67 6236B 6237B R68 6236B 6237B R69 6236B 6237B R70 6236B 6237B R71 R72 R73 6236B 6237B R74 6236B 6237B R76 53 T1 U1 3 U4 Table 6 4 Replaceable Parts Continued fxd film 330 1 1 8W fxd film 3 83k 1 1 8W fxd film 110k 1 1 8W fxd film 139 1 1 8W fxd comp 7 5k 5 1 2W fxd ww 50 5 10W fxd ww 135 5 10W fxd comp 2 2k 5 1 2W fxd comp 11k 5 1 2W fxd film 270 1 1 8W fxd film 221k 1 1 8W var ww 250 fxd film 15k 1 1 8W fxd com
16. 5 3 Initial Troubleshooting Procedure Continued Check output of 6V supply a Normal a If the output of this supply is normal Model 6236B unloaded but its voltage falls when or 18V supply loaded check the current limit adjust Model 6237B ment paragraph 5 16 steps q thru t b High low or zero b Proceed to Table 5 7 output voltage Table 5 4 Bias and Reference Voltage Check STEP ACTION Lo PROBABLE CAUSE Check 7 5V bias TP1 to Normal a Proceed to step 2 common 7 5V 5 Voltage high b Check VR3 for open Voltage low c Check VR3 for short Note A short within U1 U2 U3 or U4 can cause low 7 5V or 12 4V bias voltages Check 6 2V reference Normal a Proceed to step 3 TP2 to common 6 2V 5 Voltage high Check VR1 for open Voltage low Check VR1 and Q14 for short VR2 and Q15 for open A short within U4 could reduce this voltage Check 12 4V bias Normal Proceed 20V supply troubleshooting TP3 to common 12 4V 5 Table 5 5 High voltage Check Q11 for short Q12 for open and Z1 for open between pins 3 and 5 Low voltage Check Q11 for open Q12 for short and Z1 for open between pins 1 and 3 5 8 Table 5 5 20V Supply Troubleshooting SYMPTOM STEP ACTION RESPONSE PROBABLE CAUSE High output voltage 1 Attempt to turn down a If output voltage remains high check O1 Q15 higher than rating loop by shorting Q15 emitter and CR
17. 9 for short to base b If output voltage falls to near zero remove short from Q15 and proceed to step 2 2 Measure voltage at Out a If TP4 is approx 0 7V check for open CR6 or put of OR gate TP4 R1 and defective U1 b If TP4 is approx 0 7V check for defective Q2 Low output voltage 1 Measure voltage at out a If TP4 is between zero and O 7V check for lower than rating put of OR gate TP4 open Q1 Q15 R14 or CR59 and defective Q2 b If TP4 is approx 0 7V proceed to step 2 2 Measure voltage at TP8 a If voltage at TP8 is positive check Z1 for open between pins 5 and 13 check R8 for open and check for defective R6 or U1 b If TP8 is approx O 7V proceed to step 3 3 Measure voltage at TP7 a If TP7 is approx 0 7V check CR6 for short b If TP7 is approx 1 4V proceed to step 4 4 Measure voltage at TP13 a If TP13 is approx 0 7V replace U1 b If TP13 is zero volts check for open R10 and shorted CR2 or CR3 c If TP13 is approx 0 7V check for open R2 shorted R1 or leaky or shorted C2 Table 6 6 20V Supply Troubleshooting SYMPTOM STEP ACTION RESPONSE PROBABLE CAUSE NOTE The 20V supply must operate properly before troubleshooting the 20V supply High output voltage 1 Attempt to turn down a If output voltage remains high check Q3 CR29 more than 196 greater loop by shorting Q13 and Q13 for short than 20V supply in emitter to base fixed t
18. DEL ONLY PIN LOCATIONS FOR TRANSISTORS ARE SHOWN BELOW PL 5 TOP VIEWS 12 PIN LOCATIONS FOR INTEGRATED CIRCUITS AND THE RESISTOR NETWORK ARE SHOWN BELOW 9 8 7 e s 4 3 2 fi 10 1 re ia 15 7 Tre 21 VIEWS 7 1 53 LINE VOLTAGE SELECTOR SWITCH 240V 3 r 220V 120 TURN ON TURN OFF SJ REFERENCE AND BIAS SOE tmm CONTROL CIRCUIT zc de D 75v 6 2V 914 E Re2 IK t a M di r I00v Ac NOTES mE GND x7 p p 1 R72 33K 5 C34 2W O I f 250v 9 1 Ue Vg DSI P 2 2 i2 4V R69 SEE gt TABLE TO 6 VOLT REGULATOR 6236B CO 7 TO 18 VOLT REGULATOR 62378 Ae 278 4 1 ev cow pene OR 7124 P O ua zej 15 Fav VOLT COMP AMPL VOLTAGE 18V J METER CIRCUIT R74 SEE 46V TABLE OR R43 18V S2A o 10 2 S2ARI Ww 20V a e aa R58 VOLTMETER Z1 H 250 ADJUST 12 26 1 8W R71 R56 C21 471 ae TABLE CUR COMP M AMPL
19. MINAL OF PPLY SAMPLING POWER SU RESISTOR LOAD TERMINALS TERMINAL OF POWER SUPPLY Figure 5 2 Current Sampling Resistor Connections NOTE All instructions in this section apply to Models 6236B and 6237B unless otherwise indiated 5 15 Rated Output Tracking Meter Accuracy and Current Limit 5 16 To check that all supplies will furnish their maxi mum rated output voltage and current that the 20V outputs track each other that the front panel meters are accurate and that the current limit circuits function proceed as follows Voltmeter Accuracy a With no loads connected energize the supply con nect a digital voltmeter between the 6V terminal 18V in Model 6237B and common COM and set the 6V 18V VOLTAGE control so that the DVM indication is as near as possible to 6 volts 18 volts b Set the METER switch to the 6V 18V range and check the front panel voltmeter indication It should be within 4 of the DVM indication c Set the TRACKING RATIO control to the FIXED position and check the 20V and 20V ranges of the panel voltmeter similarly by connecting the DVM to each of these outputs in turn setting the 20V VOLTAGE control for a 20V DVM indication and verifying that the panel meter is accurate within 4 Tracking d Connect the DVM to the 20V output set the 20V VOLTAGE control for a DVM indication of 20 volts and reconnect the DVM to the 20V output without disturbing the volta
20. TRIPLE OUTPUT POWER SUPPLY MODELS 6236B AND 6237B OPERATING AND SERVICE MANUAL FOR MODEL 6236B SERIALS 1705A 00101 AND ABOVE MODEL 6237B SERIALS 1706A 00101 AND ABOVE For instruments with serial numbers above those listed a change page may be included Refer to Appendix A for manual back dating changes applying to Model 6236A and 6237 A supplies Hewlett Packard Printed February 1977 HP Part No 5950 1782 SECTION GENERAL INFORMATION 1 1 INTRODUCTION 1 2 This manual covers two triple output power supply models the 6236B and 6237B Both models are com pact general purpose bench supplies that are particularly useful for powering developmental IC circuits both linear and digital Unless one model or the other is specifically identified all information in this manual applies to both the 6236B and the 6237B CAUTION Carefully read Sections ll and lll of this manual before attempting to operate the power supply 1 3 DESCRIPTION 1 4 These constant voltage current limiting triple output supplies combine two O to 20V tracking outputs rated at 0 5 amps with an additional single output that in the Model 6236B is rated at O to 6 volts and up to 2 5 amps and in the Model 6237B is rated at O to 18 volts and 1 amps The 20V and 20V tracking outputs can also be used in series as a single O to 40V O 5 amp output Connections to the supply s output and to chassis ground are made to binding p
21. anges from 2 75A 596 at 6 volts to 1 1596 with the output shorted An output of 2 75A is 11096 of the 2 5A rated maximum at 6 volts The operating region of the 6 volt regulator output is enclosed by a heavy line in Figure 3 3 If the operating point reaches the diagonal current limit line a decrease in load resistance moves the operating point down the line reducing the output voltage 4 1 and current Current foldback is controlled by a second operational amplifier in the regulator that monitors the dc output current This current comparison amplifier takes control of the output away from the voltage comparison amplifier when the current reaches the design limit Removing the overload restores constant voltage operation automatically 4 7 The 20 volt regulator has a fixed current limit at 110 of its 0 5 amp maximum rated output but is otherwise similar to the 6 volt regulator 4 8 The O to 20 volt regulator is in turn similar to the 20 volt regulator except that it resembles complementary mirror image of the latter The output voltages of the 20volt and 20 volt supplies are both set by the same front panel control and track each other within 1 in the fixed tracking ratio mode Precise tracking of the two outputs is achieved by controlling the positive output conventionally and using that output as the reference voltage for the negative output 4 9 The O to 18 volt regulator in the Model 6237B is similar to t
22. asure ment setup while the presence of a 60 Hz fundamental usually means that an improved setup will result in a more accurate and lower value of measured ripple POWER SUPPLY CASE OSCILLOSCOPE CASE A INCORRECT METHOD GROUND CURRENT 1G PRODUCES 60 CYCLE DROP IN NEGATIVE LEAD WHICH ADDS TO THE POWER SUPPLY RIPPLE DISPLAYED ON SCOPE POWER SUPPLY CASE OSCILLOSCOPE CASE A CORRECT METHOD USING A SINGLE ENDED SCOPE OUTPUT FLOATED TO BREAK GROUND CURRENT LOOP TWISTED PAIR REDUCES STRAY PICKUP ON SCOPE LEADS POWER SUPPLY CASE OSCILLOSCOPE CASE C A CORRECT METHOD USING A DIFFERENTIAL SCOPE WITH FLOATING INPUT GROUND CURRENT PATH IS BROKEN COMMON MODE REJECTION OF DIFFERENTIAL INPUT SCOPE IGNORES DIFFERENCE IN GROUND POTENTIAL OF POWER SUPPLY 8 SCOPE SHIELDED TWO WIRE FURTHER REDUCES STRAY PICKUP ON SCOPE LEADS Figure 5 4 Ripple and Noise Test Setup 5 24 Figure 5 4B shows a correct method of measuring the output ripple of a constant voltage power supply using a single ended scope The ground loop path is broken by floating the power supply output To ensure that no potential difference exists between the supply and the oscilloscope it is recommended that they both be plugged into the same ac power bus If the same bus cannot be used both ac grounds must be at earth ground potential 5 25 Either a twisted pair or preferably a shielded two wire cable should be used to connect the output terminals of the power
23. ches about 9 volts the turn on control circuit withholds turn on bias from series regulator transistors Q1 Q3 and O7 and holds the 6 2V reference at a low value This prevents an output voltage transient by ensuring that the operational amplifiers are energized and other essential bias voltages are present before the series regulator transistors are turned on The circuit also prevents an output transient when the supply is turned off by removing the turn on bias from the series regulators and shorting the 6 2V reference supply as the voltage of the 12 4 V supply falls below 9 volts 4 41 Q13 switches the bias to the 20 volt regulator on and off Q14 switches the short across the 6 2 volt reference supply Q15 switches the bias to the 20 volt and 6 volt 18 volt regulators Q15 remains turned off until VR2 conducts at 9 volts to switch it on While Q15 is off it holds Q13 biased off and Q14 on when Q15 conducts it turns Q13 and Q14 off 4 42 Meter Circuits 4 43 Voltmeter Two of the resistors in resistor network Z1 are range resistors for the voltmeter The accurate ratio of these resistors permits a single calibration potentiometer R58 to adjust both ranges simultaneously 4 44 Ammeter The range switch connects the ammeter across the current monitoring resistor of a supply R48 in the 6 volt or 18 volt supply R8 in the 20 volt supply or R28 in the 20 volt supply Each of these resistors conducts a constan
24. d Note 1 Alternate Part Number can be tried with a high probability of success 5 45 Notice that both the commercial and alternate re placements listed in Table 6 4 apply only to the HP power supplies covered by this manual and their use in any other Hewlett Packard instrument is not necessarily recommended because of inclusion in this table 5 46 ADJUSTMENT AND CALIBRATION 5 47 Current Limit Adjustment 5 48 20V Supplies Perform the following steps to adjust the current limit circuit in the 20V or 20V supply Potentiometer R6 sets the 20V and R26 the 20V current limit a Turn the TRACKING RATIO control to the FIXED position b Turn the current limit adjustment pot R6 or R26 fully counterclockwise to its minimum setting c Connect the test circuit of Figure 5 3 to the output of the supply to be adjusted Use a 400 10W resistor for RL d Turn on the supply and set the 20V VOLTAGE control for maximum output fully clockwise e Turn the current limit pot R6 or R26 slowly clockwise until the DVM indicates a voltage drop across the shunt corresponding to a current of 0 55A 5 5 49 6V Supply Model 6236B To adjust the current limit circuit in the 6V supply proceed as follows a Check the setting of the current limit by performing steps r and s of paragraph 5 16 Be sure to set the output voltage to 6 volts If reducing the load resistance permits the current to exceed 2 9A stop turn R46 slightly clockwis
25. e 20V supply tracks that of the 20V supply within 1 for convenience in varying the symmetrical voltages needed by operational amplifiers and other circuits using balanced positive and negative inputs Turn the TRACKING RATIO control counterclock wise out of the FIXED position to set the voltage of the 20V supply lower than that of the 20V supply The negative supply can be set from a minimum of less than 0 5 volts to a maximum within 10 of the 20V supply s output Once this is done the 20V VOLTAGE control still controls both outputs and maintains a constant ratio between their voltages 3 2 3 10 Overload Protection Circuits 3 11 20 Volt Current Limit The 20 and 20V outputs are individually protected against overload or short circuit damage by separate current limit circuits adjusted at the factory to limit the output current to 0 55A 4596 This is 11096 of the maximum rated output The current limits can be set by adjusting resistor R6 for the 20V output and R26 for the 20V output See paragraph 5 47 for current limit calibration instructions No deterioration of supply performance occurs if the output current remains below the current limit setting If a single load is connected between the 20V and 20V outputs the circuit set for the lesser current limit will limit the output 3 12 6V Current Foldback Model 6236B The over load and short circuit protection circuit for the 6V output of the Model 6236B r
26. e and repeat the test If instead the current begins to fall before it reaches 2 6A turn R46 slightly counterclockwise and repeat the test b Recheck the setting and readjust R46 until the test shows that the current limit circuit begins to reduce the current when a decreasing load resistance increases it to 2 75 5 5 50 18V Supply Model 6237B To adjust the current limit circuit in the 18V supply proceed as follows a Turn current limit adjustment pot R46 fully clock wise to its minimum setting b Connect the test circuit of Figure 5 3 to the output of the 18V supply Use 180 20W resistor for RL c Turn on the supply and set the 18V VOLTAGE control for maximum output fully clockwise d Turn current limit pot R46 slowly counterclockwise until the DVM indicates a voltage drop across the shunt corresponding to a current of 1 1 A 5 5 51 Meter Calibration 5 52 Panel Voltmeters Check the accuracy of the panel voltmeter by performing steps a b and c of the procedure in paragraph 5 16 Since the same range resistors are used in both 20 volt ranges their accuracy will be the same Adjust R58 so that the percentage error in the 6V range or 18V range is equal to the error in the 20 volt ranges Turn R58 clockwise to increase the indications or counterclockwise to decrease them If R58 cannot calibrate all voltmeter ranges to within the 4 specification check the values of the resistors in the
27. e constant voltage source will deliver only that fraction of its rated output current necessary to fulfill the total current demand 3 21 Special Operating Considerations 3 22 Pulse Loading The power supply will automatically cross over from constant voltage to current limit operation in response to an increase in the output current over the preset limit Although the preset limit may be set higher than the average output current high peak currents as occur in pulse loading may exceed the preset current limit and cause crossover to occur and degrade performance 3 23 Output Capacitance An internal capacitor across the output terminals of the power supply helps to supply high current pulses of short duration during constant volt age operation Any capacitance added externally will im prove the pulse current capability but will decrease the load protection provided by the current limiting circuit A high current output pulse may damage load components before the average output current is large enough to cause the current limiting circuit to operate 3 3 3 24 Reverse Current Loading An active load connected to the power supply may actually deliver a reverse current to the supply during a portion of its operating cycle An external source cannot be allowed to pump current into the supply without risking loss of regulation and possible damage to the output capacitor To avoid these effects it is necessary to preload the supply with a d
28. educes the output current limit as the output terminal voltage decreases The operating region of the 6V output is enclosed by heavy lines in Figure 3 3 The maximum rated output current is 2 5A and the current limit is factory adjusted to operate at 2 75A 5 when the output is 6 volts At lower output voltages the circuit reduces the maximum obtainable output current linearly until 1A 15 flows when the output is shorted The shortcircuit current cannot be adjusted but R46 can be set to limit the maximum current at 6V to 2 75A 5 See paragraph 5 47 for current limit calibration instruction 3 13 18Volt Current Limit Model 6237B The 18 volt output of the Model 6237B is protected by a fixed cur rent limit circuit that operates at 1 1 A 11096 of its maxi mum rated output The circuit is similar to the ones in the 20 volt supplies See paragraph 5 47 for calibration instructions 3 14 Operation Beyond Rated Output 3 15 The supply may be able to provide voltages and currents greater than its rated maximum outputs if the line voltage is at or above its nominal value Operation can ex tend into the shaded areas on the meter faces without damage to the supply but performance cannot be guaranteed to meet specifications If the line voltage is maintained in the upper end of the input voltage range however the supply probably will operate within its specifications 3 17 Connect each load to the power supply output term
29. en OR gate diodes CR5 CR25 CR45 or defective current limit amplifier U1 U2 U3 Poor load or line regulation Check bias and reference voltages Table 5 4 b Check main rectifiers and filters for opens Oscillation or poor transient High frequency oscillations above 50 kHz can be caused by an recovery time open C4 C14 or C24 A defective output capacitor C1 C11 or C21 can cause oscillations in one of many frequency ranges Oscillation only in the current limiting mode can be caused by an open C3 C13 or C23 Transient voltage overshoot Overshoot only in the 20V supply can be caused by a at turn on or turn off shorted 013 Overshoot in all three supply outputs can be caused by an open Q14 or a shorted O15 Table 5 3 Initial Troubleshooting Procedure Check output voltage of 20V a Normal Proceed to step 2 supply b Zero volts Check ac line fuse F1 If blown proceed to paragraph 5 38 If not blown check bias and reference voltages Table 5 4 c Output voltage lower Check bias and reference voltages or higher than rating Table 5 4 Check output voltage of 20V a Normal If 20V and 20V outputs are both supply in fixed tracking ratio normal with no load a supply might mode be current limiting under load To check this adjustment see paragraph 5 16 steps I thru p b High low or zero Proceed to 20V supply troubleshooting output voltage Table 5 6 Table
30. ence in the ac potential between the power supply case and scope case Before using a differen tial input scope in this manner however it is imperative that the common mode rejection capability of the scope be verified by shorting together its two input leads at the power supply and observing the trace on the CRT If this trace is a straight line then the scope is properly ignoring any common mode signal present If this trace is not a straight line then the scope is not rejecting the ground signal and must be realigned in accordance with the manu facturer s instructions until proper common mode rejection is attained 5 28 Measurement Procedure To measure the ripple and noise on each supply output follow the steps below If a high frequency noise measurement is desired 5 5 an oscilloscope with sufficient bandwidth 20 MHz must be used Ripple and noise measurements can be made at any input ac line voltage combined with any dc output voltage and load current within rating a Connect an oscilloscope or rms voltmeter across an output of the supply as shown in Figures 5 4B or 5 4C b Energize the supply and observe the oscilloscope or meter indication The ripple and noise should not be greater than 0 35mV rms or 1 5mV peak to peak c Repeat for the remaining supply outputs 5 29 Load Transient Recovery Time Definition The time X for output voltage recovery to within Y millivolts of the nominal output voltage following a Z
31. er OR gate driver series regulator turn on control and circuit protection components of the 20 volt regulator circuit also apply to the 6 volt regulator The only difference in circuit operation lies in the control of the current comparison amplifier and thus the type of current limit the supply has 4 28 Current Foldback Circuit For this discussion refer to the Figure 7 1 schematic and to Figure 4 1 The differential input signal to the current comparison amplifier is the algebraic sum of three circuit voltages 1 The voltage across R49 ER4g remains constant at 305mV 2 The voltage across the lower part of R46 see Figure 4 1 ER49 is proportional to the regulator output voltage and equals 440mV when the supply output is 6 volts 3 The voltage across current monitoring resistor R48 ERA8 is proportional to the sum of the regulator output current and the 0 22A bias current that flows through R54 and R48 CURRENT COMPARISON AMPLIFIER lour 0 22A Q7 BIAS 0 22A Q7 BIAS Figure 4 1 Foldback Current Limit Circuit in 6V Supply 4 29 When the supply s output current is below the cur rent limit that corresponds to its output terminal voltage see Figure 3 3 the inverting input U3 6 of the current comparison amplifier is more positive than its non inverting 4 3 input U3 5 which is held at 305mV The negative am plifier output that results is clamped by CR44 and reverse biases OR gate diode CR45 leaving
32. er connector pins Below each drawing is the HP Part Number for a replacement power cord equipped with a plug of that configuration Notify the nearest HP Sales and Service Office if the appropriate power cord is not included with the instrument 2 22 Repackaging for Shipment 2 23 To insure safe shipment of the instrument it is recommended that the package designed for the instrument be used The original packaging material is reusable If it is not available contact your local Hewlett Packard field office to obtain the materials This office will also furnish the address of the nearest service office to which the instrument can be shipped and provide the Authorized Return label necessary to expedite the handling of your instrument return Be sure to attach a tag to the instrument which specifies the owner model number full serial number and service required or a brief description of the trouble OPTION 900 OPTION 90 CPTION 902 e 3 dh 8120 1351 8120 0050 8120 1369 8120 1691 Figure 2 4 Power Configurations Table 2 1 Input Power Requirements Line Voltage Range Input Current Input Power 100 100 Vac 120 Vac 220 Vac 240 Vac 87 106 Vac 104 127 Vac 191 233 Vac 208 250 Vac Standard 220 240 2 2 SECTION 1 OPERATING INSTRUCTIONS 6236B TRIPLE OUTPUT POWER SUPPLY KE E 2 0 2090 05 S in ue Wien H a vats 9 VOLTAGE H Ca i d 8 Figure 3 1 Controls a
33. er transformer are connected in one of four different ways by setting the two slide switches mounted on the circuit board These switches select one of the nominal ac input voltages for which the supply is designed 100V 120V 220V or 240V 4 4 transformer secondaries together with rectifiers and capacitor filters provide raw dc for the three output regulator circuits and for another regulator that pro vides reference and bias voltages to the output regulators 4 5 By comparing its output to a high stability refer ence the O to 6 volt regulator 6236B or O to 18 volt regulator 6237B holds its output voltage at the value determined by a front panel control Any error in the actual output as compared to the desired output is amplified by an operational amplifier and applied as feedback to control the conduction of a series regulator transistor As a result the voltage across the series transistor varies so as to hold the output voltage constant at the desired level The high gain of the voltage comparison amplifier and the stability of the reference voltage ensure that input voltage or load current variations have little effect on the output voltage 4 6 The O to 6 volt output in the Model 6236B is protected by a current foldback limiter to minimize dissipation in the series regulator transistor during overloads In a current foldback circuit the current limit depends on the output terminal voltage and in this regulator r
34. eviations c Total Quantity TQ Given only the first time the part number is listed except in instruments containing many sub modular assemblies in which case the TO appears the first time the part number is listed in each assembly d Manufacturer s Part Number or Type e Manufacturer s Federal Supply Code Number Refer to Table 6 3 for manufacturer s name and address f Hewlett Packard Part Number g Recommended Spare Parts Quantity RS for complete maintenance of one instrument during one year of isolated service h Parts not identified by a reference designator are listed at the end of Table 6 4 under Mechanical and or Miscellaneous The former consists of parts belonging to and grouped by individual assemblies the latter consists of all parts not immediately associated with an assembly 6 3 ORDERING INFORMATION 6 4 To order a replacement part address order or in quiry to your local Hewlett Packard sales office see lists at rear of this manual for addresses Specify the following information for each part Model complete serial number and any Option or special modification J numbers of the instrument Hewlett Packard part number circuit reference designator and description To order a part not listed in Table 6 4 give a complete description of the part its function and its location Table 6 1 Reference Designators assembly miscellaneous blower fan electronic part capacitor fuse circuit
35. ge control The voltage at the 20V output should be within 1 of the 20Voutput Variable Tracking Ratio e Leave the 20V VOLTAGE control set as in step d and use a DVM to monitor the voltage of the 20V supply while adjusting the TRACKING RATIO control over its VARIABLE range The 20V supply should be capable of being adjusted from less than 0 5 volts to between 18 and 22 volts Return the TRACKING RATIO control to the FIXED position NOTE Leave the TRACKING RATIO control in the FIXED position throughout the remainder of the performance test Rated Output and Ammeter Accuracy f Connect 40Q 10W load resistors across both of the 20V outputs of the supply and set the 20V VOLTAGE control for a 20V output All three supplies must be fully loaded while checking the rated output voltage and current of each supply g Connect the test setup shown in Figure 5 3 to the 6V or 18 output Make the total resistance of RL and the current sampling resistor 2 4 ohms for the Model 6236B or 18 ohms for the 6237B to permit operating the output at full load RL should have a power rating of at least 20 watts h Close the switch and set the 6V 18V VOLTAGE control so that the DVM indicates a voltage drop across the current sampling resistor that corresponds to a current of 2 5 amps 6236B or 1 0 amp 6237B i Set the METE R switch to the 6V 18V range and verify that the front panel ammeter indication is within 496 of 2 5
36. he 20 volt regulator It has a fixed current limit at 11096 of its 1 0 amp output 4 10 The reference and bias supply provides reference and bias voltages for the output regulators 4 11 The turn on turn off control circuit prevents output transients when the supply is turned on or off It does this by delaying the application of certain bias and reference voltages at turn on and removing them shortly after turn off 4 12 A three position meter switch selects which of the supplies has its output voltage and current indicated on the front panel meters The proper range of the dual range meters is selected automatically 4 13 DETAILED CIRCUIT DESCRIPTION 4 14 20 Volt Regulator 4 15 Voltage Comparison Amplifier The voltage com parison amplifier in the 20 volt supply controls the conduc tion of series regulator transistor Q1 so that the voltages at the two inputs of the amplifier remain equal A fixed voltage divider holds its inverting input U1 2 at 16mV Its non inverting input U1 3 monitors the output voltage in series with the voltage across R1 Since R2 is connected between the 6 2V reference supply and a point that feedback action holds near 16mV its current remains constant This current flows through R1 to produce a voltage drop across R1 proportional to its resistance setting thus the output voltage of the supply is proportional to the resistance setting of R1 At the output of the voltage comparison amplif
37. ier U1 1 a positive voltage change corresponds to a decrease in the conduction of O1 4 16 CR2 protect the input of the amplifier against transient overloads C2 and R4 speed up loop response time and C4 and R12 stabilize the supply s high frequency characteristics 4 17 OR Gate To permit either the voltage comparison amplifier or the current comparison amplifier to control the series regulator transistor the outputs of both amplifiers are connected to the base of driver Q2 through an OR gate composed of CR5 and CR6 CR5 is normally reverse biased by a negative output from the current comparison amplifier permitting the voltage comparison amplifier to drive Q2 through CR6 An overload drives the output of the current comparison amplifier positive forward biasing CR5 and reducing the supply output When the overload is removed CR5 is reverse biased again and the voltage com parison amplifier resumes control of the output 4 18 Driver and Series Regulator The 12 4V output of the bias supply provides the turn on bias for series regulator transistor O1 Its complete current path includes Q15 CR59 R 14 and Q1 and returns to common through current monitoring resistor R8 It is because this bias current flows through R8 that the output ammeter requires the zero offset bias circuit described in paragraph 4 43 Through the OR gate either the voltage or the current comparison amplifier controls the conduction of driver Q
38. inals using separate pairs of connecting wires This minimizes mutual coupling between loads and takes full advantage of the low output impedance of the supply Load wires must be of adequately heavy gauge to maintain satisfactory regulation at the load Make each pair of connecting wires as short as possible and twist or shield them to reduce noise pick up If shielded wire is used connect one end of the shield to the power supply ground terminal and leave the other end unconnected 3 18 If load considerations require locating output power distribution terminals at a distance from the power supply then the power supply output terminals should be connected to the remote distribution terminals by a pair of twisted or shielded wires and each load should be connected to the remote distribution terminals separately 3 19 Parallel Operation 3 20 Two or more power supplies can be connected in parallel to obtain a total output current greater than that available from one supply The total output current is the sum of the output currents of the individual supplies The output voltage controls of one power supply should be set to the desired output voltage and the other supply set for a slightly larger output voltage The supply set to the lower output voltage will act as a constant voltage source while the supply set to the higher output will act as a current limited source dropping its output voltage until it equals that of the other supply Th
39. ircuit current should also be 0 55A 5 q Model 6237B only Check the current limit of the 18V supply similarly by setting its output for 18 volts and using a DVM to measure the current which flows through a low resistance current sampling resistor The short circuit current of the 18V supply should be 1 1 A 5 r Steps r through t apply to the 6236B only Connect the test setup shown in Figure 5 3 to the 6V output Close the switch set the total resistance of R and the current sampling resistor to an initial value of 2 4 ohms or greater and set the output voltage to 6 volts s Reduce the value of RL gradually while observing the output current indicated by the DVM The current should increase to a maximum of 2 75A 5 before it begins to decrease t Connect a short across RL and then recheck the current 5 17 Load Effect Load Regulation Definition The change AEQuT in the static value of dc output voltage resulting from a change in load resistance from open circuit to the value that yields maximum rated output current or vice versa 5 18 To check the load effect a Connect a full load resistance and a digital voltmeter across the output of the 20V supply b Turn on the supply and adjust its voltage to its maximum rated value c Record the voltage indicated on the DVM d Disconnect the load resistance and recheck the DVM indication It should be within 01 plus 2mV of the read ing in step c e Re
40. le and noise and transient recovery time of the supply measuring devices must be connected as close to the output terminals as possible A measurement made across the load includes the impedance of the leads to the load The impedance of the load leads can easily be several orders of magnitude greater than the supply impedance and thus invalidate the measurement To avoid mutual coupling effects each measuring device must be connected directly to the output terminals by separate pairs of leads 5 10 When measurements are made at the front panel terminals the monitoring leads must be connected at point A as shown in Figure 5 1 and not at point B Connecting the measuring device at point B would result in a measurement that includes the resistance of the leads between the output terminals and the point of connection OUTPUT TERMINAL LOAD LEAD MONITOR HERE Figure 5 1 Front Panel Terminal Connections 5 11 Selecting Load Resistors Power supply specifica tions are checked with a full load resistance connected across the supply output The resistance and wattage of the load resistor therefore must permit operation of the supply at its rated output voltage and current For example a supply rated at 20 volts and 0 5 amperes would require a load resistance of 40 ohms at the rated output voltage The wattage rating of this resistor would have to be at least 10 watts 5 12 Either a fixed or variable resistor rheostat can be u
41. leshooting procedures in paragraph 5 35 CAUTION Before applying power to the supply make certain that its line voltage selector switch S3 is set for the line voltage to be used See CAUTION notice in paragraph 3 2 for additional information on S3 5 35 Initial Troubleshooting Procedure 5 36 If a malfunction is found follow the steps below a Disconnect input power from the supply and remove all loads from the output b Table 5 2 lists the symptoms and probable causes of several possible troubles If the symptom is one of those listed make the recommended checks If of the symptoms of Table 5 2 apply proceed to Table 5 3 This table provides an initial troubleshooting procedure that also directs you to the more detailed procedures which follow it 5 37 The numbered test points referred to in the trouble shooting procedures are identified on the circuit schematic and on the component location diagram at the rear of the manual 5 38 Open Fuse Troubleshooting 5 39 Although transients or fatigue can cause a fuse to Table 5 2 Miscellaneous Troubles SYMPTOM CHECK PROBABLE CAUSE High ripple a Check operating setup for ground loops see paragraph 5 22 b Check main rectifiers CR11 CR12 CR31 CR32 CR51 CR52 for open c Supply may be operating in current limit mode Check current limit adjustment paragraph 5 26 steps I thru t Will not current limit Check for op
42. lly displaced about the horizontal center line of the oscilloscope This center line now represents the nominal output voltage defined in the specification g Increase the sweep rate so that a single transient spike can be examined in detail 50 SECONDS 50 ys SECONDS ENOM POSITIVE OUTPUT UNLOADING TRANSIENT NEGATIVE OUTPUT LOADING TRANSIENT LOADING TRANSIENT UNLOADING TRANSIENT Figure 5 6 Load Transient Recovery Time Waveforms 5 6 h Adjust the sync controls separately for the positive and negative going transients so that not only the recovery waveshape but also as much as possible of the rise time of the transient is displayed i Starting from the major graticule division representing time zero count to the right 50us and vertically 15mV Recovery should be within these tolerances as illustrated in Figure 5 6 5 32 TROUBLESHOOTING 5 33 Before attempting to troubleshoot this instrument ensure that the fault is in the instrument itself and not in an associated piece of equipment You can determine this without removing the covers from the instrument by using the appropriate portions of the performance test of paragraph 5 6 5 34 A good understanding of the principles of opera tion is a helpful aid in troubleshooting and the reader is advised to review Section IV of the manual before begin ning detailed troubleshooting Once the principles of oper ation are understood proceed to the initial troub
43. nd Indicators i 3 1 TURN ON CHECKOUT PROCEDURE 3 2 The following steps describe the use of the Model 6236B or 6237B front panel controls and indicators illus trated in Figure 3 1 and serve as a brief check that the sup ply is operational Follow this checkout procedure or the more detailed performance test of paragraph 5 6 when the instrument is received and before it is connected to any load equipment Proceed to the more detailed procedures beginning in paragraph 5 6 if any difficulties are encountered CAUTION Before applying power to the supply make certain that its line voltage selector switch S3 is set for the line voltage to be used This switch is mounted on the circuit board behind the voltmeter and is visible through the perforations in the top cover The positions of the two white marks on the switch indicate the switch setting see Figure 3 2 If the switch setting does not correspond to the intended power source proceed to paragraph 3 4 before applying power NOTE For the Model 6237B substitute 18V for 6V in the following steps 3 1 a Connect line cord to power source and turn LINE switch D on LINE ON indicator will light b Set METER switch Q to the 6V position and with no load connected vary 6V VOLTAGE control over its range and check that the voltmeter responds to the control setting and the ammeter indicates zero c Set the 6V VOLTAGE control for a 6 volt mete
44. nd off by Q13 in the turn on control circuit 4 24 The 20 volt supply uses the output of the 20 volt supply as its reference voltage As a result both outputs are set by a single front panel control and track each other with in 196 in the fixed tracking ratio mode Two resistors in resistor network Z1 are connected in series between the 20volt and 20 volt outputs These resistors are closely matched in resistance and temperature coefficient so that the voltage across each is exactly half of the total The midpoint of this divider is connected to the non inverting input of the 20 volt supply s voltage comparison amplifier The amplifier s inverting input is connected to common through R32 to hold it at zero volts The amplifier keeps its differential input voltage at zero by matching the output voltage of the 20 volt supply to that of the 20 volt supply 4 25 In the variable tracking ratio mode the tracking ratio control connects a fixed resistor in parallel with the upper part and a rheostat the variable tracking ratio control in parallel with the lower part of the voltage divider that forms the 20 volt reference Turning the control counter clockwise reduces the resistance of the rheostat and lowers the voltage of the negative output 4 26 To 6 Volt Regulator Model 6236B 4 27 Except for differing component designations and values paragraphs 4 15 through 4 18 4 20 and 4 21 which describe the voltage comparison amplifi
45. nput Power 191 233Vac 47 63Hz single phase 240 Input Power 208 250Vac 47 63Hz single phase 910 One additional operating and service manual shipped with the power supply 1 13 Before the supply is shipped from the factory an internalline voltage selector switch is set and the proper fuse installed for the line voltage specified on the order A label on the rear heatsink identifies this line voltage option CAUTION Before applying power to the supply make certain that its line voltage selector switch S3 is set for the line voltage to be used See CAUTION notice in paragraph 3 2 for additional information The user can convert an instrument from one line voltage option to another by following the instructions in paragraph 3 4 1 14 ACCESSORIES 1 15 The accessories listed below may be ordered from your local Hewlett Packard field sales office either with the power supply or separately Refer to the list at the rear of the manual for addresses HP PART NO DESCRIPTION 14513A Rack Mounting Kit for mounting one 1 2 high supply a standard 19 relay rack 14523A Rack Mounting Kit for mounting two 3 1 2 high supplies side by side in a standard 19 relay rack Table 1 1 Specifications Model 6236B and 6237B NOTE Specifications apply to both models unless otherwise indicated INPUT POWER Standard 104 127Vac 120Vac nominal 47 63Hz single phase 112W 140VA Other line voltage op
46. nsients 4 35 Reference and Bias Supply 4 36 The reference and bias supply powers the operational amplifiers and provides the bias and reference voltages used throughout the supply A shunt zener regulates its 7 5V output A series transistor regulates its 12 4 V output using 6 2 volt zener VR1 as its voltage reference The 12 4V output provides a constant current to VR1 which is the primary voltage reference for the entire supply 4 37 Two equal resistors are connected in series across the 12 4V output To regulate this output voltage comparison amplifier U4 compares the voltage across one of these resistors to the 6 2V reference and controls the conduction of series regulator Q11 through driver Q12 The voltage drop across Q11 is controlled by feedback so that the voltages at the two inputs of U4 remain equal Driver Q12 controls Q11 by shunting part of the base bias supplied by R68 4 38 During turn on the 6 2V reference supply is temporarily shorted by Q14 in the turn on control circuit By trying to match this low reference Q11 is initially turned off While Q11 is turned off R69 bypasses current to the 12 4 V output until the output reaches 9 volts and the turn on control circuit removes the short from the reference and enables the 12 4 volt regulator to operate normally 4 4 4 39 Turn On Turn Off Control Circuit 4 40 Immediately after the supply is energized and until the output of the 12 4 volt regulator rea
47. on tinuous ground loop exists from the third wire of the input power cord of the supply to the third wire of the input power cord of the oscilloscope via the grounded power supply case the wire between the negative output terminal of the power supply and the vertical input of the scope and the grounded scope case Any ground current circulating in this loop as a result of the difference in potential Ec between the two ground points causes an IR drop that is in series with the scope input This IR drop normally having a 60 Hz line frequency fundamental plus any pickup on the unshielded leads interconnecting the power supply and scope appears on the face of the CRT 5 4 The magnitude of this remaining signal can easily be much greater than the true ripple developed between the plus and minus output terminals of the power supply and can completely invalidate the measurement 5 23 The same ground current and pickup problems can exist if an rms voltmeter is substituted in place of the oscil loscope in Figure 5 4 However the oscilloscope display unlike the true rms meter reading tells the observer imme diately whether the fundamental period of the signal dis played is 8 3 milliseconds 1 120 Hz or 16 7 milliseconds 1 60 Hz Since the fundamental ripple frequency present on the output of an HP supply is 120 Hz due to full wave rectification an oscilloscope display showing a 120 Hz fundamental component is indicative of a clean me
48. on Components Diodes CR1 CR7 and CR9 each protect the 20 volt supply from specific hazards Output diode CR1 protects the supply components if a reverse voltage is applied to the output terminals A common way for this to occur is for an unenergized supply to be connected in series with another that is energized If the output voltage is turned down quickly while a large capacitor is connected across the output CR7 protects driver Q2 from excessive dissipation by shunting some of its base current to common The series regulator diode CR9 protects the series regulator transistor from reverse voltage Reverse series regulator voltage could occur if a deenergized supply were connected in parallel with an energized one 4 22 To 20 Volt Regulator 4 23 Instead of using an NPN driver and a PNP series regulator in the negative output line as in the 20 volt regulator the 20 volt regulator uses a PNP driver and an NPN series regulator in the positive output line The 20 volt regulator circuit is the complementary equivalent of the 20 volt circuit in other respects as well Their current limit circuits operate similarly At the outputs of the current and voltage comparison amplifiers in the 20 volt circuit a negative voltage change corresponds to a decrease in series regulator conduction The turn on bias for its series regulator transistor is supplied from a positive voltage source the 7 5V bias supply and is switched on a
49. or loading and unloading the supply Connect it in the load switching circuit shown in Figure 5 5 When this load switch is connected to a 60 Hz ac input the mercury wetted relay will open and close 60 times per second The 25K control adjusts the duty cycle of the load current switching to reduce jitter in the oscillo scope display This relay may also be used with a 50 Hz ac Input 5 31 Measurement Procedure To measure the load transient recovery time follow the steps below for each supply output Transient recovery time may be measured at any input line voltage and any output voltage within rating For this supply the specified load change is between half load and full load a Connect the test setup shown in Figure 5 5 Both load resistors RL are twice the normal value of a full load resistance b Turn on the supply and close the line switch on the repetitive load switch c Set the oscilloscope for internal sync and lock on either the positive or negative load transient spike d Set the vertical input of the oscilloscope for ac coup ling so that small dc level changes in the output voltage of the power supply will not cause the display to shift e Adjust the horizontal positioning control so that the trace starts at a point coincident with a major graticule division This point then represents time zero f Adjust the vertical centering of the scope so that the tail ends of the no load and full load waveforms are symmetrica
50. osts on the front panel The supply s three outputs share a common output terminal which is isolated from chassis ground so that anyone output term inal can be grounded 1 5 All outputs are protected against overload and short circuit damage The 18V output in the 6237B and the 20V outputs in both models are protected by circuits that limit the output current to 11096 of its nominal maxi mum The overload protection circuit for the 6V output in the 6236B has a current foldback characteristic that reduces the output current as an overload increases until only 1 amp flows through a short circuit The 6V output s current limit depends on the output terminal voltage and varies linearly between 2 75 amps at 6 volts and 1 amp at zero volts 1 6 All controls meters and output terminals are 1 1 located on the front panel One voltage control sets the O to 6V 18V output and another sets the voltages of the O to 20V and O to 20V outputs simultaneously These dual tracking outputs are made more versatile by the provision of a tracking ratio control in addition to the usual voltage control With the tracking ratio control turned fully clockwise to its fixed position the dual outputs have a fixed 1 1 tracking ratio As the 20V voltage control is adjusted the voltage of the negative supply tracks the posi tive output within 1 Turning the tracking ratio control away from its fully clockwise position switches the dual tracking
51. outputs into a variable tracking ratio mode In this mode the voltage of the negative output can be set lower than that of the positive output The tracking ratio control allows the negative supply s output to be set to any value between a maximum that is within 1096 of the positive supply s output and a minimum that is less than O 5 volts Once a ratio is established by the tracking ratio control the ratio of the positive output voltage to the negative output voltage remains constant as the 20V voltage control varies the 20V output over its range 1 7 The front panel also contains a line switch and a pilot light a voltmeter and an ammeter and a meter switch that selects one of the supply s three outputs to be monitored on both dual range meters 1 8 In addition to the standard 104 to 127Vac 47 to 63Hz input three other line voltage options are available for nominal inputs of 100 220 and 240Vac The supply is furnished with a permanently attached 5 foot 3 wire ground ing type line cord The ac line fuse is in an extractor type fuseholder on the rear heatsink 1 9 SPECIFICATIONS 1 10 Table 1 1 lists detailed specifications for the power supply 1 11 OPTIONS 1 12 Options are factory modifications of a standard instrument that are requested by the customer The follow ing options are available for the instruments covered by this manual OPTION NO DESCRIPTION 100 Input Power 87 106Vac 47 63Hz single phase 220 I
52. p 240 5 1 2W fxd film 11k 1 1 8W fxd film 3 6k 2 1 8W fxd film 11k 1 1 8W fxd film 16 2k 1 1 8W fxd film 470 1 1 4W fxd ww 135 5 3W fxd ww 220 5 2W fxd ww 250 5 3W fxd ww 490 5 3W fxd ww 100 5 10W fxd ww 150 5 10W fxd ww 40 5 DW fxd ww 75 5 SW fxd film 471 1 1 8W fxd comp 33k 5 1 2W Not used fxd comp 1 1M 5 1 2W jumper installed fxd film 6 98k 1 1 8W fxd ww 10k 5 3W slide switch dual DPDT Power Transformer Dual op amp IC Operational amp IC Diode zener 6 2V Diode zener 9 09V Diode zener 7 5V Resistor network Note 1 Alternate part number See para 5 43 MFR PART NO Type MF4C T 9 Type MF4C 1 Type MF4C T O Type CEA T O EB7525 Type 247E Type 247E EB2225 EB1135 Type CEA T O Type MF4C T O Type 110 Type MEAC T O EB2415 Type MFAC T O Type MFAC T O Type MEAC T O Type MF4C T O Type MF52C T O Type 242b Type BWH Type 242b Type 242E Type 247E Type 247E Type 243E RS5 Type CMF 55 1 T 1 EB3335 EB1155 Type CMF 55 1 T 1 RS 2B CA 3458T Note 1 LM301AH 1N825 Z10939 170 1N4353B HP PART NO 0698 5663 0698 3153 0757 0466 0698 4099 0686 7525 0811 1902 0811 1905 0686 2225 0686 1135 0757 0269 0757 0473 2100 0439 0757 0446 0686 2415 0757 0443 0757 0937 0757 0443 0757 0447 0698 3506 0812 0112 0811 1763 0811 1219 0811 1801 0811 1903 0811 1906 0812 0083 0812 0097 0698 5514 0686 3335
53. peat steps a through d for each of the remain ing supply outputs POWER SUPPLY UNDER TEST COM O DIGITAL RHEOSTAT VOLTMETER CURRENT SAMPLING RESISTOR Figure 5 3 Output Current Test Setup 5 19 Source Effect Line Regulation Definition The change AEQuyT in the static value of dc output voltage resulting from a change in ac input voltage over the specified range from low line typically 104 Vac to high line typically 127 Vac or from high line to low line 5 20 To test the source effect a Connect a variable autotransformer between the in put power source and the power supply line plug b Connect a full load resistance and a digital voltmeter across the output of the 20V supply c Adjust the autotransformer for a low line input d Turn on the power adjust the output of the supply to its maximum rated voltage and record the DVM indica tion e Adjust the autotransformer for a high line input and recheck the DVM indication It should be within 01 plus 2mV of the reading in step d f Repeat steps b through remaining supply outputs e for each of the 5 21 Ripple and Noise Definition The residual ac voltage that is superimposed on the dc output of a regulated power supply Ripple and noise may be specified and measured in terms of its rms or peak to peak value 5 22 Measurement Techniques Figure 5 4A shows an incorrect method of measuring p p ripple Note that a c
54. r indication and short the 6V output terminal to COM common terminal with an insulated test lead The ammeter should indicate a short circuit output current of approximately 1 0A 1 1 A in the 6237B Remove the short from the output terminals d Set the METER switch to the 20V position and turn TRACKING RATIO control fully clockwise to the FIXED position With no load connected vary 20V VOL TAGE control 2 over its range and check that the volt meter responds to the control setting and the ammeter indicates zero e Set the 20V VOLTAGE control for a 20 volt meter indication and short the 20V output terminal to the com mon terminal with an insulated test lead The ammeter should indicate a short circuit output current of 0 55A 596 Remove the short from the output terminals f Repeat steps d and e but substitute the 20V position of the METER switch and the 20V output ter minal Adjust the 20V output for a 20V meter indication Then set the METER switch to the 20V position and check the effect of the TRACKING RATIO control on the voltage of the 20V output The 20V output should be adjustable from less than 0 5 volts to a maximum of 18 to 22 volts 3 3 If this brief checkout procedure or later use of the supply reveals a possible malfunction see Section V of this manual for detailed test troubleshooting and adjustment procedures 3 4 LINE VOLTAGE OPTION CONVERSION 3 5 To convert the supply
55. racking ratio mode 2 Measure voltage at out put of OR gate TP5 a If voltage at TP5 is zero or negative check for defective O4 b If output falls to near zero remove short from Q13 and proceed to step 2 b If TP5 is positive proceed to step 3 5 9 Table 5 6 20V Supply Troubleshooting Continued SYMPTOM STEP ACTION RESPONSE PROBABLE CAUSE 3 Measure voltage at TP14 a If TP14 is approx 0 7V check for open CR26 or defective U2 b If TP14 is approx 0 7V check Z1 for open from pin 7 to 12 or for short from pin 6 to 12 Low output voltage 1 Measure voltage at TP5 a If voltage at TP5 is zero or positive check for open more than 196 lower Q3 Q13 or R34 and defective O4 than 20V supply in fixed tracking ratio b If TP5 voltage is approx 0 7 proceed to step model 2 2 Measure voltage at TP9 If TP9 is negative check for open Z1 between pins 5 and 15 open R28 and defective R26 or U2 If TP9 is approx 0 7V proceed to step 3 3 Measure voltage at TP10 If TP10 is approx 0 7V check CR26 for short If TP10 is 1 0 to 1 4V proceed to step 4 4 Measure voltage at TP14 If TP14 is approx 0 7V replace U2 If TP14 is zero volts check for shorted CR22 or CR23 If TP14 is approx 0 7 check 2 1 for open between pins 6 and 12 or short between pins 7 and 12 and check for leaky or shorted C12 Table 5 7 6V or 18V Supply Troubleshooting High o
56. ries regulator transistor so as to prevent ER4g and thus the supply s output current from increasing further At 0 25 ohms R48 develops 672mV at 2 69 amps Since 0 22 amps of the current through R48 is bias current for Q7 the nominal current limit corresponding to a 5 volt output is 2 69 amps minus 0 22 amps or about 2 47 4 31 If the load resistance continues to decrease it pulls the output voltage lower This reduces ER46 until at a zero output voltage ER46 becomes zero leaving ER4g equal in magnitude to ER49 This 305mV drop across R48 corre sponds to a 1 22 amp current through R48 and a 1 amp shortcircuit current at the output of the supply 4 32 In the 6 volt regulator as in the 20 volt regulator the turn on bias current for the series regulator transistor is switched on and off by Q15 in the turn on control circuit to prevent output voltage transients 4 33 To 18 Volt Regulator Model 6237B 4 34 Except for differing component designations and values paragraphs 4 15 through 4 21 which describe the voltage comparison amplifier OR gate driver series regu lator current limit circuit turn on control and circuit protection components of the 20 volt regulator circuit also apply to the 18 volt regulator In the 18 volt regulator as in the 20 volt regulator the turn on bias current for the series regulator transistor is switched on and off by Q15 in the turn on control circuit to prevent output voltage tra
57. rument see the CAUTION notice in paragraph 3 2 2 9 Location 2 10 This instrument is air cooled Sufficient space should be allotted so that a free flow of cooling air can reach the rear of the instrument when it is in operation It should be used in an area where the ambient temperature does not exceed 40 C up to 55 C with derating 2 11 Outline Diagram 2 12 Figure 2 1 illustrates the outline shape and dimen sions of this supply 2 13 Rack Mounting 2 14 This instrument may be rack mounted in a standard 19 inch rack panel either by itself or alongside a similar Ge unit Figures 2 2 and 2 3 show the components of the rack mounting kits available for this power supply Ordering information for rack mounting accessories is given in para Figure 2 3 Rack Mounting Two Units graph 1 14 2 1 2 15 Input Power Requirements 2 16 Depending on the line voltage option ordered the supply is ready to be operated from one of the power sources listed in Table 2 1 The input voltage range and the input current and power at high line voltage and full load is listed for each option A label on the rear heat sink identifies the line voltage option of your supply All options of this model operate from a 47 63 Hz single phase line 2 17 If desired the user can easily convert the unit from any of these options to another by following the instructions in paragraph 3 4 A unit is converted by resetting an internal line vol
58. sed as the load resistance Using a rheostat alone or in series with a fixed resistor is often more convenient than using fixed resistors as loads because the latter may be more difficult to obtain in the exact resistance required A supplier of rheostats appropriate for testing these supplies is listed in Table 5 1 5 13 Output Current Measurements For accurate out put current measurements a current sampling resistor should be inserted between the load resistor and the output of the supply An accurate voltmeter is then placed across the sampling resistor and the output current calculated by dividing the voltage across the 5 2 the sampling resistor by its ohmic value The total resistance of the series combination should be equal to the full load resistance as determined in the preceding paragraphs Of course if the value of the sampling resistor is very low when compared to the full load resistance the value of the sampling resistor may be ignored The meter shunt recommended in Table 5 1 for example has a resistance of only 1 milliohm and can be neglected when calculating the load resistance of the supply 5 14 Figure 5 2 shows a four terminal meter shunt The load current through a shunt must be fed to the extremes of the wire leading to the resistor while the sampling connec tions are made as close as possible to the resistance portion itself CURRENT SAMPLING TERMINALS EXTERNAL LOAD TO UNGROUNDED TO GROUNDED TER
59. spond to those on the component location diagram and in the troubleshooting procedure in Section V The tinted areas on the schematic indicate components and jumpers used in one model only P O Zei REC TURA ON zer CIRCUIT in gr 60 xdi K VO 60 REG GRAS E wi CC cn 8 KS CR 1 P O Keo B SE SE REG E ge ES Ser 8 8145 SUPPLY a l PLO ABOV Models 6236B 6237B Component locations SCHEMATIC NOTES ALL COMPONENTS ARE LOCATED ON PC BOARD UNLESS OTHERWISE INDICATED 2 t DENOTES CHASSIS MOUNTED COMPONENTS 3 DENOTES CONSTANT VOLTAGE FEEDBACK PATH DENOTES CURRENT LIMIT FEEDBACK PATH ALL RESISTORS IN OHMS I 8W 1 UNLESS OTHERWISE INDICATED THE SQUARE PLATED PADS ON THE P C BOARD INDICATE ONE OF THE FOLLOWING A PIN 1 OF AN C OR TRANSFORMER B POSITIVE END OF A POLARIZED CAPACITOR C CATHODE OF A DIODE OR EMITTER OF A TRANSISTOR 4 5 6 IN RESISTOR NETWORK Z1 Z1 J AND 21 ARE MATCHED TO WITHIN 1 AND Zi L AND 21 ARE MATCHED TO WITHIN 0 5 AND TRACK WITHIN 50 PPM C FOR 100V OR I20V OPERATION USE A 2A FUSE HP PART NO 2110 0002 FOR 220V OR 240V OPERATION USE 1A FUSE HP PART NO 2110 0001 o THE LOCATION AND PART NO OF R46 IS THE SAME FOR MODELS 6236B AND 62378 BUT ITS ORIENTATION ON THE BOARD DIFFERS THE TINT AREAS ON THE SCHEMATIC INDICATE COMPONENTS AND JUMPERS THAT ARE USED IN ONE MO
60. ss than 0 35mV rms and 1 5mV p p 20 Hz to 20 MHz DRIFT Stability All Outputs Less than 0 1 plus bmV dc to 20Hz during 8 hours at constant line load and ambient after an initial warm up time of 30 minutes 1 16 INSTRUMENT AND MANUAL IDENTIFICATION 1 17 Hewlett Packard power supplies are identified by a two part serial number The first part is the serial number prefix a number letter combination that denotes the date of a significant design change and the country of manufac ture The first two digits indicate the year 10 1970 11 1971 etc the second two digits indicate the week and the letter A designates the U S A as the country of manufacture The second part is the power supply serial number A different sequential number is assigned to each power supply starting with 00101 1 18 If the serial number on your instrument does not agree with those on the title page of the manual Change Sheets supplied with the manual or Manual Backdating Changes define the difference between your instrument and the instrument described by this manual 1 19 ORDERING ADDITIONAL MANUALS 1 20 One manual is shipped with each power supply unless Option 910 is ordered for each extra manual Addi tional manuals may be purchased from your local Hewlett Packard field office see the list at the rear of this manual for addresses Specify the model number serial number prefix and the HP Part Number provided on the title page
61. supply to the vertical input terminals of the scope When using a twisted pair care must be taken that one of the two wires is connected to the grounded input terminal of the oscilloscope to ensure that the supply output is safely grounded When using shielded two wire it is essential for the shield to be connected to ground at one end only to prevent ground current flowing through this shield from inducing a signal in the shielded leads 5 26 verify that the oscilloscope is not displaying ripple that is induced in the leads or picked up from the grounds the scope lead should be shorted to the scope lead at the power supply terminals The ripple value obtained when the leads are shorted should be subtracted from the actual ripple measurement 5 27 In most cases the single ended scope method of Figure 5 4B will be adequate to eliminate extraneous ripple so that a satisfactory measurement may be obtained However in more stubborn cases or if high frequency noise up to 20 MHz must be measured it may be necessary to use a differential scope with floating input as shown in Figure 5 4C If desired two single conductor shielded cables may be substituted in place of the shielded two wire cable with equal success Because of its common mode rejection a differential oscilloscope displays only the difference in signal between its two vertical input terminals thus ignoring the effects of any common mode signal pro duced by the differ
62. t bias current for its series regulator transistor in addition to the supply s output current If no compensation were used this additional current would raise the indicated output by up to 896 of full scale The resistor networks connected to each range of the ammeter selector switch apply a bias to the meter to offset this error R59 calibrates all ammeter ranges SECTION V MAINTENANCE 5 1 INTRODUCTION 5 2 Upon receipt of the power supply the performance test of paragraph 5 6 can be made This test is suitable for incoming inspection Section Ill contains a quick but less comprehensive checkout procedure that can be used in lieu of the performance test if desired 5 3 If a fault is detected in the power supply while making the performance test or during normal operation proceed to the troubleshooting procedure in paragraph 5 32 After troubleshooting and repair repeat the performance test to ensure that the fault has been properly corrected and that no other faults exist Before performing any mainte nance checks turn on the power supply and allow a half hour warm up 5 4 TEST EQUIPMENT REQUIRED 5 5 Table 5 1 lists the test equipment required to perform the various procedures described in this section 5 6 PERFORMANCE TEST 5 7 The following test can be used as an incoming inspection check and appropriate portions of the test can be repeated to check the operation of the instrument after repairs If the correct result is no
63. t obtained for a particular check proceed to the troubleshooting procedures of para graph 5 32 CAUTION Before applying power to the supply make certain that its line voltage selector switch S3 is set for the line voltage to be used See CAUTION notice in paragraph 3 2 for addi tional information on S3 Table 5 1 Test Equipment Required REQUIRED CHARACTERISTICS Digital Voltmeter Sensitivity 100mV full scale min Input impedance 10 megohms min Variable Voltage Transformer Range 90 130 Vac Equipped with voltmeter accurate within 1 volt Sensitivity 100uV cm Differential input Oscilloscope Repetitive Load Sw Rate 60 Hz 2us rise and fall time Resistive Loads Value See paragraph 5 11 Tolerance 5 Current Sampling Resistor Shunt Value See paragraph 5 13 Accuracy 196 minimum 5 1 Measure dc voltages calibration procedures Vary ac input Display transient re sponse and ripple and noise waveforms Measure transient response Power supply load resistor fixed resistor or rheostat Measure output current RECOMMENDED MODEL HP 3490A HP 180C with 1821A and 1801A or 1803A plug ins See Figure 5 5 James G Biddle Lubri Tact Rheostat Simpson Portable Shunt 06703 5 8 General Measurement Techniques 5 9 Connecting Measuring Devices To achieve valid results when measuring the load effect PARD ripp
64. tage selector switch replacing the fuse and changing the line voltage tag CAUTION f the supply might possibly have been converted to a line voltage option other than the one marked on its identifying label without being relabeled in some way check the setting of the line voltage selector switch and the fuse rating before applying power See CAUTION in paragraph 3 2 2 18 Power Cable 2 19 To protect operating personnel the National Electrical Manufacturers Association NEMA recommends that the instrument panel and cabinet be grounded This instrument is equipped with a three conductor power cable The third conductor is the ground conductor and when the cable is plugged into an appropriate receptacle the instru ment is grounded The offset pin on the power cable three prong connector is the ground connection In no event shall this instrument be operated without an adequate cabinet ground connection 2 20 To preserve the protection feature when operating the instrument from a two contact outlet use a three prong to two prong adapter if permitted by local regulations and connect the green lead on the adapter to ground 2 21 Model 6236B and 6237B supplies are equipped at the factory with a power cord plug appropriate for the user s location Figure 2 4 illustrates the standard configu rations of power cord plugs used by HP Above each draw ing is the HP option number for that configuration of pow
65. tions are listed in paragraph 1 12 DC OUTPUT AND OVERLOAD PROTECTION to 20V Outputs Maximum rated output current is 0 5A Short circuit output current is 5 5 and a fixed current limit circuit limits the output of each supply to this maximum at any output voltage setting Unbal anced loads within current rating are permitted Switching to the variable tracking ratio mode allows the 20V output to be varied from less than 0 5V to within 10 of the voltage setting of the 20V output Model 6236B O to 6V Output Maximum rated output current is 2 5A at 6V The maximum available output current decreases with the output voltage setting A current foldback circuit limits the output to 2 75A 5 at 6 volts and with decreasing voltage reduces the current limit linearly to 1A 15 at zero volts short circuited 1 2 Model 6237 B O to 18V Output Maximum rated output current is 1 0A Short circuit output current is 1 1A 5 and a fixed current limit circuit limits the output to this maximum at any output voltage setting TRACKING ACCURACY The 4 20V and 20V outputs track within 196 with the TRACKING RATIO control in the FIXED position LOAD EFFECT Load Regulation All Outputs Less than 0 01 plus 2mV for a full load to no load change in output current SOURCE EFFECT Line Regulation All Outputs Less than 0 01 plus 2mV for any line voltage change within rating PARD Ripple and Noise All Outputs Le
66. tor a Remove the top and bottom covers from the instru ment b Remove the collector screws and unsolder the base and emitter leads from the board to remove the transistor c To replace the transistor follow the below reassembly order as viewed from the bottom of the heat sink collector screws P C board heat sink two insulating bushings in collector screw holes in heatsink silicon grease Dow DC 5 or HP 8500 0059 mica insulator another coating of silicon grease transistor lock washers and hex nuts d Resolder the emitter and base pins to the circuit board 5 43 Semiconductor Replacement 5 44 Table 6 4 contains replacement data for the semiconductors used in this power supply When replacing a If voltage at TP12 is positive check for shorted R49 open R48 open Z1 between pins 5 and 14 and defective R46 or U3 If TP12 is approx 0 7 proceed to step 3 If TP11 is approx 0 7V check CR46 for short If TP11 is approx 1 4V proceed to step 4 If TP15 is approx 0 7 replace U3 If TP15 is zero volts check for open R50 and shorted CR42 or CR43 c If TP15 is approx 0 7V check for shorted R41 open R42 or leaky or shorted C22 a semiconductor use the listed Hewlett Packard part or exact commercial replacement if these are available If neither of these are immediately available and a part is needed without delay for operation or troubleshooting verification the parts designate
67. ummy load resistor so that the power supply delivers current through the entire operating cycle of the load device 3 25 Reverse Voltage Protection Internal diodes con nected with reverse polarity across the output terminals protect the output electrolytic capacitors and the driver transistors from the effects of a reverse voltage applied across a supply output Since series regulator transistors cannot withstand reverse voltage either diodes are also connected across them When operating supplies in parallel these diodes protect an unenergized supply that is in parallel with an energized supply OUTPUT TERMINAL VOLTAGE ev NOMINAL CURRENT LIMIT OPERATING REGION HE 115A SHORT CIRCUIT CURRENT MAY VARY t15 FROM UNIT TO UNIT OUTPUT CURRENT AMPERES NOTE THE LOWER END POINT OF THE CURRENT LIMIT LINE IS NOT ADJUSTABLE THE UPPER END POINT IS SET AT THE FACTORY FOR 2 75A 59 BETWEEN ITS END POINTS THE ACTUAL CURRENT LIMIT IS A STRAIGHT LINE FUNCTION Figure 3 3 Current Limit Characteristics of the 6V Supply Model 6236B SECTION IV PRINCIPLES OF OPERATION 4 1 OVERALL DESCRIPTION 4 2 This section presents the principles of operation of the Models 6236B and 6237B Triple Output Power Supply Throughout this section refer to the combined schematic diagram of Figure 7 1 NOTE All information in this section applies to both models unless otherwise indicated 4 3 The two primary windings of the pow
68. utput voltage 1 Attempt to turn down loop If output voltage remains high check O7 Q15 higher than rating by shorting Q15 emitter to base and CR49 for short If output voltage falls to near zero remove short from Q15 and proceed to step 2 Measure voltage at output If TP6 is approx O 7V check for open CR46 or of OR gate TP6 R41 and defective U3 If TP6 is approx 0 7V check for defective Q8 Low output voltage Measure voltage at output If TP6 is between zero and 0 7V check for open lower than rating of OR gate TP6 Q7 Q15 R54 or CR59 and defective O8 If TP6 is approx O 7V proceed to step 2 Table 5 7 6V or 18V Supply Troubleshooting Continued SYMPTOM STEP ACTION RESPONSE PROBABLE CAUSE 2 Measure voltage at TP12 3 Measure voltage at TP11 4 Measure voltage at TP15 blow it is a good idea to inspect the unit for obvious shorts such as damaged wiring charred components or extraneous metal parts or wire clippings in contact with circuit board conductors before replacing the fuse The rating of the correct replacement fuse depends on the line voltage option of the instrument for Options 100 or 120 use a normal time constant 2 amp fuse HP Part No 2110 0002 for Options 220 or 240 use a normal time constant 1 amp fuse HP Part No 2110 0001 5 40 REPAIR AND REPLACEMENT 5 41 Series Regulator Replacement 5 42 To remove and replace a series regulator transis
69. v MIT 20v CR52 R48 6 SEE Ee BEAD h TABLE Y 612 CR49 0 596 1 8W mmm 200017 REGULATOR Ear Va 20V R73 E SEE TABLE 9 7 5V Zi E 137K Den A 12 4V WW 1 1 8W 2 8 oto 25a 612 OR S28 0 5 8 1 0 5 2 S2BRI R57 Sd 4 221 R59 AMMETER 12 4V 250 ADJUST CUR COMP AMPL 13 CUR LIMIT T ADV 4 40 e 5 S2BR2 21 i 612 0 5 1 8W EG e Tra CR9 12 Y V 7 5V AWA ccs O TO 20 VOLT REGULATOR R28 1 1 25 MODEL 62368 62378 0 5 Eau OUTPUTS OTO 20V ATOTO 0 5A O TO 20V AT OA 5W O OTO 6V AT UP TO 2 5A O TO ATO TO 1A 2 1 12V 1804F 50V MITAD XJ C27 5600 F 25V 3000uF 40V 5 Gi 0 47 F 35V 0155 35V Ze ER R42 8 66K 1 178 2 87K 1 1 8W 200V 12119 R48 025 1 2 5W 0 625 1 2 5W I E Vw R76 eu R50 330 1 178W 3 83K 1 1 8W b aL R54 50 5 IOW 135 5 IOW 9 Sze 50V R55 2 2K 5 V2W Up 5 1 2W R67 135 5 3W 220 5 2W 13 15 5 6 R68 250 5 3W 490 5 3W A TRACKING L don gt R69 100 5 IOW 150 5 IOW RTO 40 596 EW 75 5 5W cR26 VARIABLE R73 NOT USED LIM 5 1 2W FIXED R74 JUMPER INSTALLED 6 98K 1 1 8W oR RES R33 GATE 10 DRIVER 15k R24 12 3w 18 VARIABLE gt 21 0 Yo v Lie Es ga FIXED iji Sou A T EA Een Figure 7 1 Models 6236 and 6237B Schematic Diagram 7
70. voltmeter circuit 5 53 Panel Ammeter Check and calibrate the panel ammeter by following the steps below a Connect the test setup shown in Figure 5 3 to the 6V or 18V output Make the total resistance of RL and the current sampling resistor 2 4 ohms Model 6236B or 18 ohms 6237B to permit operating the supply at its full rated output RL should have a power rating of at least 20 watts b Close the switch and set the 6V 18V VOLTAGE control so that the DVM indicates an output of 2 5A 6236B or 1 0A 6237B c Check and record the panel ammeter accuracy on the 6V or 18V range d Check each of the 20 volt ammeter ranges similarly using the same test setup but making RL a 400 10W resistor and setting the voltage control for a output current Record the panel ammeter accuracy on each 20 volt range e Turn R59 clockwise to increase the indications on all three ranges or counterclockwise to decrease them f If R59 cannot calibrate all three ammeter ranges to within the 4 specification check the values of the resis tors in the circuit including current monitoring resistors R8 R28 and R48 SECTION VI REPLACEABLE PARTS 6 1 INTRODUCTION 6 2 This section contains information for ordering re placement parts Table 6 4 lists parts in alpha numeric order by reference designators and provides the following information a Reference Designators Refer to Table 6 1 b Description Refer to Table 6 2 for abr

HP 6236B

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