LP-525K REV-F 12-23-02.qxd
Contents
1. CAUTION Do not connect the alligator clips to any AC power source or to a DC power source greater than 35VDC Failure to comply with this warning may result in damage to this instrument SPECIFICATIONS Input Impedance 1MQ Input Overload Protection 50V DC continuous Thresholds Logic 1 Logic 0 TTL 2 3 25V 0 80 1V CMOS 7096 Vcc 30 Vcc Response better than 25 nanoseconds Pulse Detector Power Requirements 5V Vcc Q 30mA 15V Vcc Q 40mA Operating Temperature 40 C to 85 C 1 5 millisecond pulse stretcher CONSTRUCTION Introduction The most important factor in assembling your LP 525K Logic Probe Kit is good soldering techniques Using the proper soldering iron is of prime importance A small pencil type soldering iron of 25 40 watts is recommended The tip of the iron must be kept clean at all times and well tinned Safety Procedures Wear eye protection when soldering Locate soldering iron in an area where you do not have to go around it or reach over it Do not hold solder in your mouth Solder contains lead and is a toxic substance Wash your hands thoroughly after handling solder Be sure that there is adequate ventilation present Assemble Components In all of the following assembly steps the components must be installed on the top side of the PC board unless otherwise indicated The top legend shows where each component goes The leads pass through the corresponding holes in the board and are2. backing off to expose the glue Place the PC board assembly into the case as shown in Figure 12 Use two 4 screws to hold the case together Do not over tighten or the holes may strip out Cut a 13 16 piece of red shrink tubing and slide it over the probe tip until it touches the plastic case Shrink the tubing by heating it with your soldering iron Be sure the soldering iron does not contact the tubing or plastic case o nra o 4 This completes the assembly procedure Your Logic Probe is now ready for testing Figure 11 Red Shrink Tubing 4 x 5 8 Screw Bottom Label 4 x 5 8 Screw Figure 12 CAUTION Do not connect the alligator clips to any AC power source or to DC power source greater than 35VDC Failure to comply to this warning may result in damage to this instrument TESTING YOUR DIGITAL PROBE Checking out your Logic Probe for proper operation is fairly easy All that is needed is a 9V battery or other DC power source 5 10V Connect the red alligator clip to the positive terminal of the battery and the black clip to the negative terminal Set the PULSE MEM switch to the PULSE position and the TTL CMOS switch to the TTL come on and stay on until the switch is flipped back to the pulse position No LED s should light up when the tip is not touching anything open circuit The logic probe should operate at the followi
3. indicate the condition of the node Refer to the chart below to interpret the LED readings To prevent power supply spikes connect the leads as close to the node to be tested as possible Interpreting the LEDs All LEDs off 1 Test point is an open circuit 2 Out of tolerance signal LED 3 Probe not connected to power 4 Node or circuit not powered O LED Off Equal brightness of the HI and LO LED indicates approx 50 duty cycle square wave LED Blinking High frequency square wave greater than approximately SMHz Logic 0 with positive pulses present Low duty cycle since HI LED is not If duty cycle were increased the HI LED would start to turn on Logic 1 with negative pulses present High duty cycle since LO LED is not on If duty cycle were reduced the LO LED would start to turn on SCHEMATIC DIAGRAM 906zNZzZ did MOL1UDITIg HOiU5ITU Q3au OOtNT sa SvTtNT 4A4nToo 92 3S id og T0621 zem StTPNT 9062NZ TS TZ va 900z TOeZW z3 vin tO6 NZ zo Spt NT bO6ENZ be 906ENZ HOST zo ata 4nsoo woot SvTPNt HOOT ou 8 3 10 Elenco Electronics Inc 150 W Carpenter Avenue Wheeling IL 60090 847 541 3800 http www elenco com e mail elenco 9 elenco com
4. 01 C5 047uF Capacitor May marked 473 C6 001uF Capacitor May be marked 102 C3 200pF Capacitor May be marked 201 D3 1N4148 Diode see Figure 4 D4 1N4148 Diode see Figure 4 C4 005uF Capacitor May be marked 502 C7 1uF Capacitor May be marked 104 ASSEMBLE COMPONENTS TO THE PC BOARD Refer to the top legend on the PC board install and solder the following components Insert the IC socket into the PC board with the notch in the direction shown on the top legend Solder the IC socket into place Insert the IC into the socket with the notch in the same direction as the notch on the socket PC Board Before installing snip off the tabs Mount the switch so that the legs are touching the PC board U1 14 pin IC Socket U1 LM2901 IC see Figure 5 SW1 Switch see Figure 6 Q1 2N3906 Transistor see Figure 7 L1 Q2 2N3904 Transistor see Figure 7 SW Switch see Figure 6 Q4 2N3904 Transistor see Figure 7 Mount the transistor with the flat side in the direction shown on the top legend Leave 1 4 between the part and PC board Flat Side Marking Figure 7 Cut a 3 8 piece of tubing for each LED lead to be used as stand offs Mount the LED with the flat side in the direction shown on the
5. 0kO Resistor brown black yellow gold R6 100kO Resistor brown black yellow gold R7 100kO Resistor brown black yellow gold see Figure 1 R22 30kO Resistor orange black orange gold R21 2000 Resistor red black brown gold R3 4 7MQ Resistor yellow violet green gold Tos 1 1 R5 100kO Resistor brown black yellow gold see Figure 1 R4 4 7kO Resistor yellow violet red gold ASSEMBLE COMPONENTS TO THE PC BOARD Refer to the top legend on the PC board install and solder the following diodes capacitors and jumper wires When mounting diodes Form jumper wire from discarded When mounting diodes horizontally vertically mount as resistor lead mount as indicated by the band indicated by band Diodes have polarity Diodes have polarity o IL LI Figure 2 Figure 3 Figure 4 D1 1N4148 Diode see Figure 2 D2 1N4148 Diode see Figure 2 J Jumper Wire see Figure 3 J Jumper Wire see Figure 3 C1 001uF Capacitor May be marked 102 OJ Jumper Wire see Figure 3 D5 1N4148 Diode see Figure 4 J Jumper Wire see Figure 3 J Jumper Wire see Figure 3 D6 1N4002 Diode see Figure 4 C2 100pF Capacitor May be marked 1
6. IL 7 il 00039 8 Assembly and Instruction Manual Elenco Electronics Inc Copyright 1992 Elenco Electronics Inc REV F Revised 2003 753241 PARTS LIST If you are a student and any parts are missing or damaged please see instructor or bookstore If you purchased this LP 525K Logic Probe kit from a distributor catalog etc please contact Elenco Electronics address phone e mail is at the back of this manual for additional assistance if needed RESISTORS Qty Symbol Description Color Code Part 03 R21 R23 R24 2002 596 1 4W red black brown gold 132000 1 R16 2kO 596 1 4W red black red gold 142000 O1 R4 4 7 596 1 4W yellow violet red gold 144700 1 R14 5 1kO 5 1 4W green brown red gold 145100 1 R11 15kQ 5 1 4W brown green orange gold 151500 1 R13 18kQ 5 1 4W brown gray orange gold 151800 2 R10 R15 20kQ 5 1 4W red black orange gold 152000 2 R12 R22 5 1 4W orange black orange gold 153000 Ri R5 R8 R19 R20 100kO 5 1 4W brown black yellow gold 161000 1 R17 120 5 1 4W brown red yellow gold 161200 1 R18 150 5 1 4W brown green yellow gold 161500 3 R2 R3 R9 4 7MQ 5 1 4W yellow violet green gold 174700 CAPACITORS Qty Symbol Description Part Qty
7. Symbol Description Part 1 C2 100pF 101 Discap 221017 1 C4 005uF 502 Discap 235018 1 C3 200pF 201 Discap 222010 1 05 047uF 473 Discap 244780 2 C1 C6 001uF 102 Discap 231036 1 UT 1uF 104 Discap 251010 SEMICONDUCTORS Qty Symbol Description Part Qty Symbol Description Part 1 D6 1N4002 Diode 314002 Q1 3 5 2N3906 Transistor 323906 5 D1 D5 1N4148 Diode 314148 1 Ui LM2901 IC 332901 2 Q2 Q4 2N3904 Transistor 323904 3 L1 L3 LED 350001 MISCELLANEOUS Qty Description Part Qty Description Part 1 PC Board 517014 1 Label Front 724002 O2 Switch SPDT 541024 11 Label Back 724003 1 Probe Tip 616001 1 Wire 1 5 814220 01 Case 623005 03 Wire 2 cond 870500 2 Screw 4 x 5 8 643450 3 Tubing 20 890020 1 Socket 14 pin 664014 1 Shrink Tubing red 890312 1 Alligator Clip Black 680001 1 Solder Tube 9ST4 1 Alligator Clip Red 680002 PARTS IDENTIFICATION D Sj mM Capacitor Transistor Ge IDENTIFYING RESISTOR VALUES Use the following information as a guide in properly identifying the value of resistors BAND 1 BAND 2 Resistance 1st Digit 2nd Digit Tolerance Color igi Color Multiplier Tolerance Black Back 0 10 Brown 70 5 Red 2 Red 100 11 Orange 1 000 Red 2 Yellow 10 000 Green Blue Bue 6 Violet Gray Gay 8 White Wie 9 BANDS 1 2 Multiplier Tolerance N i 9 IDENTIFYING CAPACITOR VALUES Capacitors will be identified by their capaci
8. ircuit paths and creates a short circuit This is usually caused by using too much solder To correct this simply drag your soldering iron across the solder bridge as shown ASSEMBLE COMPONENTS TO THE PC BOARD Refer to the top legend on the PC board install and solder the following resistors Stand resistor on end when called for R13 18kO Resistor brown gray orange gold R9 4 7MQ Resistor yellow violet green gold R10 20kO Resistor red black orange gold R23 2000 Resistor black brown gold see Figure 1 R1 100kO Resistor brown black yellow gold R24 2000 Resistor red black brown gold R12 30kQ Resistor orange black orange gold R20 100kO Resistor brown black yellow gold see Figure 1 R17 120kO Resistor brown red yellow gold see Figure 1 R19 100kO Resistor brown black yellow gold R2 4 7MQ Resistor yellow violet green gold R15 20kQ Resistor red black orange gold R16 2kQ Resistor red black red gold i 1 1 1 1 1 1 gea 0 Save 5 discarded leads for jumper wires R14 5 1kO Resistor green brown red gold R11 15kO Resistor brown green orange gold 1 1 1 1 1 1 1 1 1 1 R8 10
9. ng logic levels when the power supply voltage is precisely set to position Touch the probe tip to the positive side of the 5VDC battery the PULSE LED should blink once and the HIGH LED should light up Place the probe tip to the negative terminal and the LOW LED should light up To check the operation of the memory switch set the PULSE MEM switch to the MEM position and set the TTL CMOS switch to the TTL position Now touch the probe tip to the positive side of the battery The PULSE LED should DTL TTL Position Logic 0 under 8V 1V Logic 1 above 2 3V 25V CMOS Position Logic O under 1 5V 2V Logic 1 above 3 5V 35V TROUBLESHOOTING CHART Power Cord leads reversed Check U1 C7 or D6 HIGH LED or LOW LED never lights Check LED by shorting pins Condition No LED s light up 1 2 or 14 to negative supply Check U1 Check U1 R9 to R15 Check Q3 Q5 U1 Check LED 3 Q1 Q4 D3 D4 Noise on power line HIGH or LOW LED always on Pulse LED always on PULSE LED never flashes All LED s flash OPERATING INSTRUCTIONS To operate the logic probe connect the two alligator clips to the circuit DC power supply red clip to the positive voltage black to ground BE SURE THE CIRCUIT SUPPLY IS UNDER 35V OR DAMAGE MAY OCCUR TO THE PROBE Set the logic family switch to TTL or CMOS Touch the probe tip to the circuit node to be LED STATES INPUT analyzed The LED display on the probe body will light to
10. nput and the comparator turns off The short pulse on the input is thus stretched to 1 5 milliseconds The input pin 8 of the PULSE LED driver is biased to 2 5VDC by resistors R19 and R20 The input is biased to 3VDC by resistors R6 and R18 The 1 5 milliseconds pulse from the pulse stretcher grounds the input through diode D5 turning the comparator on and lighting the PULSE LED When the PULSE MEM switch is in MEM Q5 is also turned on causing the input of the comparator to go to 5VDC This keeps the comparator on even after the input returns to 3VDC When the PULSE MEM switch is in PULSE the feedback path to the input is broken and the LED is lit only for the duration of the 1 5 milliseconds pulse Thus each time the input signal changes state the PULSE LED is activated for 1 5 milliseconds When observing low frequency signals the PULSE LED provides an immediate indication of this pulse activity By observing the HI and LOW LEDs the polarity of the pulse train can be determined Low frequencies cause the PULSE LED to blink once for each transition High frequencies cause the LED to flash at a rate that makes it appear to be on continuously When the PULSE MEM switch is in MEM a single input pulse will cause the PULSE LED to come on and stay on until the switch is returned to the PULSE position The input impedance of the LP 525 is 1MQ This eliminates any loading effect on the circuit under test
11. soldered on the foil side Use only rosin core solder of 63 37 alloy DO NOT USE ACID CORE SOLDER What Good Soldering Looks Like A good solder connection should be bright shiny smooth and uniformly flowed over all surfaces Types of Poor Soldering Connections 1 Insufficient heat the solder will not flow onto the lead as shown 1 Solder all components from the copper foil side only Push the soldering iron tip against both the lead and the circuit board foil Soldering Iron Component Lead E 2222222 V Soldering iron positioned Circuit Board incorrectly 2 Insufficient solder let the solder flow over the connection until it is covered Use just enough solder to cover the connection 2 Apply a small amount of solder to the iron tip This allows the heat to leave the iron and onto the foil Immediately apply solder to the opposite side of the connection away from the iron Allow the heated Soldering Iron Solder 3 Excessive solder could component and the circuit foil to melt the solder Allow the solder to flow around the connection Then remove the solder and the iron and let the connection cool The solder should have flowed smoothly and not lump around the wire lead Here is what a good solder connection looks like i make connections that you did not intend to between adjacent foil areas or terminals Solder bridges occur when solder runs between c
12. t see schematic diagram One comparator drives the HI LED and the other drives the LOW LED The comparator output goes low lighting the LED when the input is more positive than the input To measure TTL circuits the TTL CMOS switch is set to TTL and the red and black alligator clips are connected to 5VDC and ground The input pin 5 of the HI comparator is then biased to 2 3VDC by resistor network R9 through R15 Thus the LED lights when the probe tip is more positive than 2 3VDC To measure CMOS circuits the HI comparator changes to 3 5VDC or 70 of the supply voltage The input of the LOW comparator is biased to 8VDC for TTL operation and 1 5VDC or 3096 of the supply voltage for CMOS operation The LOW LED thus lights when the probe tip is connected to voltages less than 8 or 1 5VDC The pulse LED is controlled by a bipolar edge detector circuit which responds to both positive and negative transients This circuit is made up of capacitors C2 and C3 transistors Q1 through Q4 and the associated resistors When the circuit is activated by pulses as short as 25 nanoseconds a negative pulse is applied to the input pin 11 of the pulse stretcher comparator The comparator then turns on and is held by the feedback resistor R8 The ground level on the output pin 13 causes C5 to discharge through R17 In approximately 1 5 milliseconds the voltage on the input pin 10 becomes more negative than the i
13. tance value in pF picofarads nF nanofarads or uF microfarads Most capacitors will have their actual value printed on them Some capacitors may have their value printed in the following manner The maximum operating voltage may also be printed on the capacitor ms 9 TT T2 T4 T5 T5 Note The letter R may be used at times First Digit to signify a decimal point as in 3R3 3 3 Second Digit Multiplier Talatang The letter M indicates a tolerance of 20 The letter K indicates a tolerance of 10 The letter J indicates a tolerance of 5 v Maximum Working Voltage The value is 10 x 1 000 10 000pF or O1uF 100V METRIC UNITS AND CONVERSIONS Multiply Unit By 000000000001 000000001 micro 000001 milli 001 unit 1 kilo 1 000 mega 1 000 000 Means Pico nano Abbreviation 1 000 pico units 1 nano unit 1 000 nano units 1 micro unit 1 000 micro units 1 milli unit 1 000 milli units 1 unit 1 000 units 1 000 kilo units 1 kilo unit 1 mega unit CIRCUIT DESCRIPTION The Elenco Model LP 525K Logic Probe kit is a convenient and precise instrument for use in the measurement of logic circuits It displays logic levels high or low and voltage transients down to 25 nanoseconds The LED readouts provide instant response to the logic state To detect the high and low logic levels the LP 525 uses two comparators of a Quad Comparator LM2901 Integrated Circui
14. top legend Flat Side 8 Marking Figure 8 L1 LED L2 LED see Figure 8 L1 L3 LED see Figure 8 R18 150kQ Resistor brown green yellow gold Q5 2N3906 Transistor see Figure 7 Q3 2N3906 Transistor see Figure 7 see Figure 8 Install SW1 first Install the power cord as shown in Figure 9 Pull the power cord wires apart about 2 inches on one end Strip the insulation off of both wires to expose 1 4 of bare wire s A Solder wire to clip Note that one wire is ribbed then bend tabs over on the edge Solder the red Figure 9 insulated vire alligator clip to the ribbed wire Solder the black clip to the round wire On the other side of the power cord pull the wires apart 1 2 Strip 1 4 of insulation off of both wires Make a knot to serve as a strain relief about 1 inch from the end Solder the ribbed wire to hole marked and the round wire to the hole Figure 10 marked see Figure 10 Install the probe tip as shown in Figure 11 Using the 1 1 2 wire strip 1 4 of insulation off of both ends Solder one end to point P on the PC board Solder the other end of the wire to the probe tip groove Install the two labels to the case as shown in Figure 12 Be careful to place the labels on neatly and correctly Peal the
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