Pride DX-300 CHAPTER 1
Contents
1. Ref Description MFR Part No ASSY HIGH VOLTAGE PWR SUPPLY 2 01 0300 00 HIGH VOLTAGE PWR SUPPLY PCB 82 0300 01 Resistors Ref Description MFR Part No R1 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R2 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R3 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R4 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R5 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R6 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R7 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R8 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R9 Resistor Carbon Film 150K Ohm 2W 10 06 1504 02 R10 Resistor Carbon Film 150K Ohm 2W 10 06 1504 02 R11 Resistor Carbon Film 150K Ohm 2W 10 06 1504 02 R12 Resistor Wire wound 25 Ohm 10W 10 17 2500 10 Capacitors Ref Description MFR Part No C3 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C4 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C5 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C6 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C7 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C8 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C9 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C10 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C11 Capacitor Electrolytic 100uF 450V 23 0107 45 C12 Capacitor Electrolytic 100uF 450V 23 0107 45 C13 Capacitor Electrolytic2. C47 1 2 C48 C48 Figure 3 41 Cathode Circuit The RL2 DPDT relay on the main R F board is used solely for switching the receiver preamp in and out of the antenna circuit It is controlled by both the RECEIVE switch on the front panel and the grounding contact on the RL1 4PDT relay RADIO ANT IN R53 12vDC 82 0300 03 SRF INPUT AND C 12 via 54 and Low o Voltage Supply PCB REC AMP Figure 3 42 Receiver Preamp Circuit 32 Copyright O 2004 CBTricks com Pride DX300 3 5 Safety Interlock PCB From Pin 3 of the HY Power Supply PCB CHAPTER 3 INTERLOCK 59 LL r LI LI 1 r 1 LI LI LI LI To L8 Plate Choke 10pH C3 005uF 82 0300 04 3KV SAFETY L INTERLOCK PCB Figure 3 5 Safety Interlock Circuit Never turn on the amp with cover off The shorting safety switch will cause the high voltage to short out If this happens it will usually takes out R59 or the bridge rectifier 3 6 Wattmeter PCB To RF Input and Control PCB 1 C57 may have a 1 39pF SM installed 1yF 50v 82 0300 06 METER PCB z Figure 3 6 Wattmeter Circuit 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 4 Maintenance The following information is presented so that the competent service technician should have no trouble in performing routine service on the Pride DX 300 Lethally high voltages are present inside the amplifier unit Never remove either top or bottom
3. Pride DX300 CHAPTER 7 7 5 Bias Circuit Modification Version1 Nomad Radio Mod The Bias voltage is a Negative 82 Volt supply which is set between 65 and 68 volts to the tube The most common part failure is the bias pot RV1 500ohm 2W linear pot and an 82 Volt 5 Watt zener D25 One substitute for the stock D25 setup is three 20 Volt 5 Watt zeners in series For people who want a bias control that will turn all the way down past cutoff use a string of six for the R version of the tube and five of them for the stock B tube It looks a little over the top but never comes back blown 350v DC from C34 5K 50W Low Voltage Power Supply PCB Wirewound 22K To Pin 16 on the RF Input and Control PCB D3 D1 DB 20 SW 1N5357 A D5 Install D1 D5 for a 4CX250B Install D1 D6 for a 4CX250R Remove R38 R39 D25 Remove RY1 and install 1K 5V Potentiometer Figure 7 1 Zener Bias Mod The space the zeners occupy here is normally where the two very hot 10 Watt resistors R38 and R39 go You can locate a single 5K 50W resistor off the board to do that job It runs cooler and leaves room for five or six zeners in series on the low voltage power supply PCB With six zeners installed the pot has an end to end range of 40 Volts more or less For the 250R this is from 120 to 80 For the 250B with just five zeners installed is 100 to 60 This permits biasing the tube past cutoff and provides a rollback or carrier control fo
4. 0138 00 S6 Switch Phonetic 1 Pole 5 Position 40 3000 00 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 6 CHASSIS Cont Ref Description MFR Part No L7 ASSY Tank Coil 15 80 Meters 01 0300 15 L12 Choke RF 1mH 160 MA 24 1006 00 Capacitor Strap 85 0300 17 Ref Description MFR Part No Dial Figure Black DX 300 32 0299 00 Knob Black DX 300 32 2912 00 Knob Black DX 300 32 2912 01 CAP Knob DX 300 42 0290 00 LED1 L E D Red Diffused 49 5024 00 LED2 L E D Red Diffused 49 5024 00 LED3 L E D Red Diffused 49 5024 00 LED4 L E D Red Diffused 49 5024 00 Clip amp Ring LED Panel Mounting 05 5024 00 Z1 Parasitic Suppressor Grid 4Turns 22 01 0300 07 Resistor Carbon Film 150 Ohm 1 2W R65 Z2 ASSY Parasitic Suppressor 01 0300 05 Resistor Carbon Film 100 Ohm 2W R62 Resistor Carbon Film 100 Ohm 2W R63 Resistor Carbon Film 100 Ohm 2W R64 L9 Choke RF Plate 55uH 24 0014 00 T1 Transformer DX 300 High Voltage 25 0300 01 T2 Transformer DX 300 Low Voltage 25 0300 02 BL1 Blower High Output Modified 87 1250 00 Flange Outlet For Blower PN 87 1250 00 87 1250 01 Ref Description MFR Part No V1 Tube 4CX250B 65 0250 00 Socket Electron Tube E F Johnson 124 110 09 0250 00 Screen bypass Cap Round Frame E F Johnson 124 113 001 Socket Chimney E F Johnson 124 0111 011 09
5. 0250 01 Ref Description MFR Part No PL 1 Line Cord 3 Wire 1118W Molded Plug 28 3186 00 PL 2 SO239 RF Input PL 3 SO239 RF Output PL 4 Recept 3 COND Round Metering Jack 09 7135 00 RV1 POT 500 Ohm 2 25W 10 SCR ADJ 625 SHFT 18 5001 02 F1 Fuse AGC 10 AMP 65 0010 00 Fuse Extractor Post 67 1200 00 Ref Description MFR Part No Foot Rubber 31 32 75 2135 00 Cover 85 0300 11 Bottom Plate 85 0300 14 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 7 Circuit Modifications 7 0 Introduction NOTE Exercise a great deal of care with any Modifications done Due to the high Voltage and close proximity of the surrounding components If done wrong you could destroy components or KILL yourself If you have even the slightest doubts or the proper equipment it would be wise to have someone else you trust perform the mod for you SO TAKE YOUR TIME AND DOUBLE CHECK YOUR WORK 7 1 Screen LED Modification The Screen LED LED4 seldom lasts long but we use a 2W part for R35 and R36 same resistance values The LED will still die if there s a surge on the screen but the larger resistors take it better than the stock 1 2W parts 7 2 Screen Supply Modification The Pride DX300 has no screen regulation and should Nomad Radio http www nomadradio com is working on a new Low Voltage PCB have seen Prides with a 25K 10W to ground on the 350v supply A p
6. 100uF 450V 23 0107 45 Diodes Ref Description MFR Part No D1 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D2 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D3 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D4 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D5 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D6 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D7 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D8 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 6 3 B CIRCUITRY Safety Interlock Ref Description MFR Part No ASSY B CIRCUITRY Safety Interlock 01 0300 16 PCB B CIRCUITRY 82 0300 04 Inductors Ref Description MFR Part No L8 ASSY Toriod Inductor 10uH 10 Windings 01 0300 28 Resistors Ref Description MFR Part No R59 Resistor Carbon Film 150K Ohm 2W 10 06 1504 02 Capacitors Ref Description MFR Part No C56 Capacitor Ceramic Disk 0 005uF 3KV 08 0502 00 Ref Description MFR Part No Ground Strap Safety Interlock 85 0300 15 Bracket B Circuitry 85 0300 18 32 Copyright 2004 CBTricks com Pride DX300 6 4 LOW VOLTAGE PWR SUPPLY CHAPTER 6 Ref Description MFR Part No ASSY LOW VOLTAGE PWR SUPPLY 01 0300 02 LOW VOLTAGE PWR SUPPLY PCB 82 0300 02 Resistors Ref Description MFR Part No R27 Resist
7. OUTPUT QO OO Q OO Q OO O QQ Q OO Q OO O QQ Q OO qp PLATE TUNE High voltage present when covers removed Fr amp 3 o D S E S E WARNING DANGER D qp t SE o gt Bee Gass z g E 5225 32 o 378 5 0 oats o Ao 928 s 2E S s 26 set 2 2 9zi Ez o 5 Al o 32 Copyright 2004 CBTricks com REAR VIEW Pride DX300 CHAPTER 5 5 8 Chassis Layouts Top and Bottom BL1 Ol IO T1 amp m 4 vu T TII RF Input and Control PCB 32 Copyright O 2004 CBTricks com Pride DX300 6 1 HIGH VOLTAGE PWR SUPPLY 1 CHAPTER 6 Ref Description MFR Part No ASSY DX 300 HIGH VOLTAGE PWR SUPPLY 1 01 0300 01 PCB DX 300 HIGH VOLTAGE PWR SUPPLY 82 0300 01 Resistors Ref Description MFR Part No R13 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R14 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R15 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R16 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R17 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R18 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R19 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R20 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R21 Resistor Carbon Film 150K Ohm 2W 10 06 1504 02 R22 Resistor Carbon Film 150K
8. Ohm 2W 10 06 1504 02 R23 Resistor Carbon Film 150K Ohm 2W 10 06 1504 02 R24 Resistor Carbon Film 6 8 Ohm 2W 5 06 0680 02 R25 Resistor Carbon Film 6 8 Ohm 2W 5 06 0680 02 R26 Resistor Wire wound 25 Ohm 10W 10 17 2500 10 Capacitors Ref Description MFR Part No C14 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C15 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C16 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C17 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C18 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C19 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C20 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C21 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C22 Capacitor Electrolytic 100uF 450V 23 0107 45 C23 Capacitor Electrolytic 100uF 450V 23 0107 45 C24 Capacitor Electrolytic 100uF 450V 23 0107 45 Diodes Ref Description MFR Part No D9 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D10 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D11 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D12 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D13 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D14 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D15 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D16 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 32 Copyright 2004 CBTricks com Pride DX300 6 2 HIGH VOLTAGE PWR SUPPLY 2 CHAPTER 6
9. cover when power line is connected DO NOT attempt to operate unit when covers are removed 1 Lethal voltages would be open to contact 2 Protective interlock on top cover will short circuit the high voltage power supply attempting to operate under these conditions can cause damage to power supply amplifier tube or both 3 Attempting to operate the unit with bottom cover removed causes loss of air pressure to the tube and can cause rapid failure of the tube 4 Attempting to operate the unit with top cover removed with the interlock blocked may make the amplifier erratic in tuning and performance due to the high level of R F on the top chassis coupling to the coaxial input cable at the rear of the chassis If repairs should be necessary contact the factory or a repair facility with proper equipment and technical experience for the servicing of high power amplifiers If covers need be removed allow two minutes after turning the unit off and unplugging the line cord before removing covers 4 0 Plate current measurement Plate current can be monitored by means of an external meter plugged into the METERING jack on the back panel The voltmeter should be connected as below 1 5 3v Figure 4 0 Meter Connection The following chart converts voltage as read at the metering jack to actual plate current 17V 2 50mA 1 02V 300mA 34V 100mA 1 19V 350mA 51V 2 150mA 1 36V 400mA 68V 200mA 1 53V 450mA 85V 250mA 1
10. 04 3899 sales mouser com Nomad Radio 1615 Bardstown Road Louisville KY 40205 http Awww nomadradio com info nomadradio com Add on and replacement accessories for various amateur CB radios and amplifiers 32 Copyright 2004 CBTricks com Nomad Radio Heavy Duty High Voltage power supply board kit for the Pride DX 300 base amplifier f Tma EE gt m a B S RANAANENEN The Kit includes all the parts to build a single PCB HV Power Supply that replaces both HV PCB in a Pride DX300 This PCB lets you completely remove the original two H V circuit boards and install the single piece replacement The Kit has the following components 1 HDHV version 3 printed circuit board 6 180uF 450 Volt radial snap in electrolytic capacitors 2 5 ohm 5 Watt wirewound power resistors 7 240K ohm 2 Watt carbon film bleeder resistors 26 1N5408 3 Amp 1000 Volt rated rectifier diodes Nomad Radio 1615 Bardstown Road Louisville KY 40205 http www nomadradio com info nomadradio com 1N5408 x24 32 Copyright 2004 CBTricks com
11. 70V 500mA 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 4 4 1 Bias voltage adjustment The following adjustment is from the factory manual you may want to do it another way The bias voltage should rarely need attention If however the tube is changed or the adjustment is otherwise disturbed the following procedure should be adhered to 1 Be sure the amplifier has been off for several minutes to allow enough time to discharge the power supplies Remove the bottom cover 2 Place a jumper wire or clip lead from point A on the main circuit board to ground Refer to pictorial for specific placement of the jumper 4 91 qo D30 A 3 y C50 5 R50 e 6 n a GND 15 x L11 an D32 R57 R58 lt dMe Figure 4 1 Jumper A O 3 Replace bottom cover 4 Place a 50ohm dummy load on the output connector of the amplifier 5 Turn the unit on and allow it to warm for 60 seconds 6 Place the TUNE STANDBY OPERATE switch into the OPERATE position and adjust bias control for a reading of 35mA or 12V as read at the metering jack 7 Turn off unit and allow it to discharge for several minutes before restoring it to normal configuration This completes the bias adjustment 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 4 4 2 Wattmeter Calibration The following adjustment is from the factory manual you may want to do it bypassing the safety interlock and adj
12. B 1800VDC 500m B ne 2 Dm pee 2 O AEE o g 1 1 LI a 1 pr LI R9 1 de R21 1 D2 ca C11 DIO lt R14 1 TC22 150k I i ac iur SRE i OS hor fw 450V 5 450V D3 lt R3 C5 D11 lt R15 C16 LI c LI LI 9 L LI LI 180DVAC DA R4 C5 i D12 RIE c17 500MA R12 E R26 de R22 1 Q 25 Tor Sok D Troe 0 RED 100pF 1 w ADS RS c7 450v 2W I r tow D13 R7 Lote asov i T1 i 1 1 1 LI pe i 1 LI LI 1 a LI D7 R7 cg R11 x D15 lt R19 C20 de R23 1 un ien 180K i l NEU E 1 100pF 2 a i pesi Wo L D8 ps c10 450v D16 lt R2 c21 n LI LI o o Pie in be BOR Tr i BOARD JA Sp R25 TMeter Jack Dis TRADE o N 0 ME 58 208 os LE equ murus RED re MAD D9 D16 1N4007 Coenen Con R13 R20 470K 1 2W 1 82 0300 01B ri opyng pe Inge OM HIGH VOLTAGE POWER SUPPLY C14 C21 DlyF 1KV Figure 3 1 High Voltage Power Supply 32 Copyright O 2004 CBTricks com Pride DX300 CHAPTER 3 3 2 Screen and Bias Supplies PCB The screen and bias supply is also bridge rectified but with a center tapped transformer and filter string that allows a split output voltage Approximately 700 VDC is developed across the two 40pf filter caps C33 C34 but due to the circuit configuration this shows up as 350 and 350 VDC The 350 VDC is fed through a 300hm metering resistor R36 to the screen c
13. FR Part No D29 Diode Signal 1N914 48 0914 00 D30 Diode Rectifier 1A 50V Plastic 48 4001 00 D31 Diode Rectifier 1A 50V Plastic 48 4001 00 D32 Diode Signal 1N914 48 0914 00 Relays Ref Description MFR Part No RL1 Relay 4PDT Allied Control TY154 4C 12DC 41 1024 00 RL2 Relay 2PDT Potter amp Brumfield R10 E1 Y2 V185 41 1022 01 Transistors Ref Description MFR Part No Q1 Transistor 2N2905 PNP SI Switching 48 2905 00 Q2 Transistor 2N2905 PNP SI Switching 48 2905 00 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 6 6 6 WATTMETER PCB Ref Description MFR Part No ASSY WATTMETER PCB 01 0300 09 WATTMETER PCB 82 0300 06 Inductors Ref Description MFR Part No T4 ASSY Toroid Coil 17 Winding 01 0300 27 Resistors Ref Description MFR Part No RV2 Potentiometer Trimpot 50K Ohm 1 4 W 19 5003 00 R60 Resistor Carbon Film 15K Ohm 1 2W 5 06 1503 00 R61 Resistor Carbon Film 68 Ohm 2W 5 06 6800 02 Capacitors Ref Description MFR Part No C57 4 60pF C58 Capacitor Dipped Mica 330pF 5 DM 15 21 1331 00 C59 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C60 Capacitor Ceramic 0 1uF 100V 08 0104 02 Diodes Ref Description MFR Part No D33 Diode Signal 1N914 48 0914 00 Meters Ref Description MFR Part N
14. Pride DX 300 CHAPTER 1 1 0 INTRODUCTION In putting together this manual started with the Pride DX300 factory manual added information that was missing and in error put together new updated schematics and PCB layouts The Pride DX 300 is a high frequency linear amplifier covering the Amateur bands from 3 5 to 30 MHz Pride Electronics in San Diego CA was a manufacturer of RF amplifiers and VFO s as well as frequency counters The products that Pride built where assembled by handicap people hence the slogan printed on the back of the amplifier Manufactured with Pride by the Handicap think that most of the DX300 s where built between 1977 and 1978 Some people say that Pride was in the business of selling CB amplifiers under the guise of amateur radio amps The Pride DX300 has no screen regulation no feedback and no screen or grid metering it was designed to provide a medium power amplifier with high power gain at LOW COST It does have a receiver preamplifier and automatic RF actuated switching The amp has no mistuning protection but with care anyone should have not problems with tuning it using the TUNE mode 1 1 SPECIFICATIONS Power Ratings Mode Drive Power SSB 15 watts peak 1000 watts PEP input 650 watts nominal peak output any band CW 10 12 watts 750 watts input 50 duty cycle 500 watts nominal output any band AM 4 6 watts 500 watts input 5 minute cycle 300 watts nominal output a
15. This will normally result in approximately 100watts output for three to four watts of driving power 8 Un key the exciter and place the TUNE STANDBY OPERATE switch in the OPERATE position When the exciter is keyed again the power output will be somewhat higher and the SCREEN indicator may glow brightly again Repeat the procedure as before tuning the PLATE LOADING and PLATE TUNING controls alternately for maximum output The PLATE TUNING control should always be the last control that is adjusted Power output should be about 250watts for five watts drive at this point in the tune up procedure When proper loading is accomplished the SCREEN indicator should glow only dimly The plate current as read on an external meter should be in the neighborhood of 200 250ma 32 Copyright 2004 CBTricks com Pride DX 300 CHAPTER 2 9 For SSB operation drive power should now be gradually increased to 10 or 12 watts and the unit peaked for maximum output This can be done using the carrier insertion control on some exciters or if this is not available a steady tone may be applied to the microphone input When maximum power has been achieved operation consists of simply keying the microphone and speaking The SSB delay switch should be in the on position which will give the R F actuated relays a time delay so that they won t chatter during transmission During the SSB transmission power output peaks will occur so rapidly that the output meter will n
16. at part number would be R10 E1 W4 V185 The pre amp relay RL2 is usually a Potter amp Brumfield The original part number would be R10 E1 Y2 V185 That crosses over to a NTE R16 11D3 12 It is a 2PDT type with 3 amp contacts and a 12 volt 185ohm coil 8 2 Band Switch If the amp is keyed up and the band switch S5 is turned while still keyed the band switch is ruined for good the contacts will burn so badly that the entire switch will have to be replaced The Band switch haven t found a replacement 8 3 Input Coil Information T3 the 9 1 impedance step up input transformer 3 wires 10 windings trifilar L5 10 meters is 12 turns 24 shows 0 75 uH 13 TURNS APPROX 0 9 uH works better on 27 MHz Core 7 16 OD x 7 32 ID x 5 32 thick Yellow black Probably a 6 powdered iron core L4 15 meters is 17t shows 1 4 uH same core L3 20 meters is 23t shows 2 4 uH same core L2 40 meters is 31t on a larger core shows 6 pH Core 11 16 OD T 68 x 3 8 ID x 7 32 thick red probably 2 powdered iron mix L1 200 pH RF choke 8 4 Z1 Information 4 Tums 22 R65 150 Ohm 122 Z1 Grid Parasitic Suppressor ASSY 8 5 Z2 Information If the resistors look like toast new resistors should be n installed before you try to run it 100 Ohm 2W q 3 8 Ie If the resistors look okay and it has all 3 of them leave it alone If you replace them we recommend using a 5 Watt rated 100 ohm carbon film or metal film resist
17. cription MFR Part No D17 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D18 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D19 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D20 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D21 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D22 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D23 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D24 Diode Rectifier 1N4007 1 AMP 1000PIV 48 4007 00 D25 Diode Zener 82V 5W 1N5375 48 5375 00 D26 Diode Rectifier 1N4001 1A 600PIV 48 4001 00 D27 Diode Rectifier 1N4001 1A 600PIV 48 4001 00 D28 Diode Rectifier 1N4001 1A 600PIV 48 4001 00 32 Copyright 2004 CBTricks com Pride DX300 6 5 RF INPUT AND CONTROL BOARD CHAPTER 6 Ref Description MFR Part No ASSY RF INPUT AND CONTROL 01 0300 03 RF INPUT AND CONTROL PCB 82 0300 03 Inductors Ref Description MFR Part No L1 Choke SUB MIN 200UH NIN Q47 80 METERS 24 2000 00 L2 ASSY Coil Input Toroid 40 METERS 01 0300 26 L3 ASSY Coil Input Toroid 20 METERS 01 0300 25 L4 ASSY Coil Input Toroid 15 METERS 01 0200 24 L5 ASSY Coil Input Toroid 10 METERS 01 0300 23 L10 Choke RF 22 uH 24 2200 00 L11 Choke RF 0 82 uH 24 0820 00 L14 Choke SUB MIN 200uH NIN Q47 24 2000 00 T3 ASSY Input Transformer 3 Wire
18. d it also simplifies repairs RF actuated switching eliminates the need for switching contacts on the exciter which are not found on some of the lower powered rigs on the market An internal receiver preamp provides approximately 10db of gain on the higher frequencies Power supplies 3 1 High Voltage Supply PCB The high voltage supply consists of the plate supply transformer located on the top of the chassis and the two rectifier filter boards below chassis directly under the plate transformer A bridge rectifier circuit is used which allows good utilization of the transformer Both circuit boards are the same with the exception of the jumpers JP1 and JP2 which determine whether the filter capacitors are on the high side of the series filter string or on the low side The low side board also contains two 6 80hm 2W metering resistors R24 R25 Each board contains one half of the bridge rectifier circuit with appropriate jumpers between the boards The filter string consists of six 100pf electrolytic capacitors C11 C12 C13 C22 C23 C24 in series with voltage equalizing resistors R9 R10 R21 R22 R23 across each one The time constant of the filter when no current is being drawn is approximately 20 seconds so that supply will be largely discharged 60 seconds after turn off ALWAYS CHECK The high voltage developed by the supply is approximately 2200 VDC no load and 1800 VDC at 500mA e 2200VDC No ine To Safety Interlock PC
19. erson could build a regulator for the supply So check his web site for details 7 3 Tube Oscillation Adding another capacitor on the B side of the plate choke can stop oscillation of the tube Typically 001uF at 3000Volts 7 4 Wattmeter PCB Modification Nomad Radio Mod On the small circuit board bolted to the rear of the meter the output coax should be SOLDERED DIRECTLY TO THE BOARD First unplug the two coax cables from it Loosen the nuts on the meter posts and GENTLY pull the board away from the meter body You will need to unsolder the bare ground wire from the inboard lower corner Heat the solder to the four pins where the two coaxes were plugged in and pull them completely out of their holes You will need to ream the two ground holes the ones on the outside edge out to a hole size of about 3 32 of an inch You also need to clear any leftover solder from the two holes where the coax center wires attach Remove the spring contacts from both the coax cables that you unplugged from the meter board Strip about 3 8 of an inch from the end of each You should also pull off the shrink tubing that covers the coax braid Tin each of these wire ends to hold all those loose strands together Now insert the tinned wire ends back into the four holes in the meter board Solder them in place and that skinny bare ground wire on the corner of the board When the meter board is mounted back onto the meter posts 32 Copyright 2004 CBTricks com
20. f people using a 4CX350B but I haven t tested that 4CX250B 7203 4CX250R 7580W Characteristics Plate Dissipation Max 250 Watts Screen Dissipation Max 12 Watts Grid Dissipation Max 2 Watts Frequency for Max rating CW 500 MHz Amplification Factor 5 Filament Cathode Oxide Coated Voltage 6 0 Volts Current 2 6 Amps Capacitance Grounded Cathode Input 4 5 pf Output 04 pf Feedthrough 15 7 pf Capacitance Grounded Grid Input 4 5 pf Output 01 pf Feedthrough 13 0 pf Cooling Forced Air Base 9 Pin Special Air Socket SK 600A Air Chimney SK 606 Boiler Length 2 46 in 62 50 mm Diameter 1 64 in 41 70 mm Weight 4 oz 113 gm Characteristics Plate Dissipation Max 250 Watts Screen Dissipation Max 12 Watts Grid Dissipation Max 2 Watts Frequency for Max rating CW 500 MHz Amplification Factor 5 Filament Cathode Oxide Coated Voltage 6 0 Volts Current 2 6 Amps Capacitance Grounded Cathode Input 4 8 pf Output 04 pf Feedthrough 17 5 pf Capacitance Grounded Grid Input pf Output pf Feedthrough pf Cooling Forced Air Base 9 Pin Special Air Socket SK 600A Air Chimney SK 606 Boiler Length 2 46 in 62 50 mm Diameter 1 64 in 41 70 mm Weight 4 oz 113 gm 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 5 5 0 Low Voltage Supply PCB 8s0 00 0 S8 3 6 5 4 ee o D26 R42 PRIDE DX300 Bi Linear Amplifier LOW Voltage Power Suppl
21. ials for voltage readings and locations Voltages on the tube socket are as follows Pin 1 350 VDC 10 Pins 3 and 7 6 3VAC 10 Grid Connection 82 to 64 VDC depending on the setting of bias control and mods installed Caution When measuring the B supply 2200 VDC use only a meter which is designed to measure 2kv plus safety during operation at high voltage levels 8 Restore the unit to its original condition 4 5 Preventive Maintenance There are four circuit boards in the bottom compartment have all the wires attached to them with small spring metal socket contacts Pull each of the socket contacts one at a time If any of them that feel loose when you pull on it should be GENTLY squeezed with a small pair of pliers so that it has some friction when you push it back onto its circuit board pin Check for burnt components on each of the circuit boards replace as needed and look for reason for failure Important When you put the bottom cover back on check the seal and be sure that you put all the screws in Also be sure that the 3 screws on the back of the top cover are installed Now take a close look at that big copper hair pin Z2 that attaches to the tube clamp topside If the resistors look like toast new resistors should be installed before you try to run it If the resistors look okay and it has all 3 of them leave it alone If you replace them we recommend using a 5 Watt rated 100 ohm carbon film or metal film res
22. istor They will withstand more abuse than the original 2 Watt rated parts DO NOT use wire wound resistors Period Both Mouser Electronics and Westgate Labs sell this resistor Check the main fuse F1 in the back and check the rating printed on it The correct size is 10 Amp 125 Volt or 250 Volt A 32 Volt fuse is NOT the right type for this amplifier 32 Copyright 2004 CBTricks com Pride DX300 4 6 Tube Replacement If a tube failure does occur a likely reason for this would be a loss of one or more of the required operating voltages at the tube socket Thus before a tube is replaced the voltage measurement procedure should be followed to determine if further repairs are necessary If all required voltages are present the tube can then be replaced safely The 4CX250R is a ruggedized 4CX250B with a better cathode and more gain It is pin and heater compatible with the 250B The Eimac catalogue says The 4CX250R 7580W will replace the 4CX250B in equipment where the range of bias adjustment will tolerate this higher perveance tube and where the tuning range can compensate for the small differences in input and output capacitances It means you may need a bit more negative G1 bias to set the required standing current 100mA per tube Brand of tube types that work in the DX300 Eimac Best Taylor Very Good Svetlanta Russian Very Good Edcom Not Good Tubes that will work 4CX250B 4CX250R CHAPTER 4 Have heard o
23. itch into the operate position 4 Apply approximately three watts of drive to the input of the amplifier with band switch set to the appropriate band 5 Spread or compress the turns of the toroid for the band in use to obtain the lowest SWR reading possible 6 Restore the unit to its original configuration 32 Copyright O 2004 CBTricks com Pride DX300 CHAPTER 4 4 4 Voltage Checks As the voltages present on the DX 300 chassis are potentially lethal the procedure below must be followed when checking voltages 1 Make sure that the unit is unplugged and has been off for several minutes to allow all voltages to bleed to zero 2 Remove the top cover Doing so will engage the safety interlock so never apply A C power when this cover is removed 3 Loosen and remove the anode clamp from the 4CX 250B tube V1 Remove the tube the ceramic chimney and the anode clamp from the chassis Make sure the parasitic suppressor Z2 is suspended away from any chassis parts 4 Replace the top cover on the amplifier 5 Lay the amplifier on its side or top and remove the bottom cover Remember the tube must be removed or it will be damaged by the loss of cooling air when the unit is powered without the bottom cover 6 Apply A C power to the unit WARNING Extreme caution must be used when working with voltages of this level Always be cautious and alert while working on the live chassis 7 Refer to the individual circuit board pictor
24. l Rights Reserved Rev 1 2 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 5 5 5 Safety Interlock PCB PRIDE DX300 Bi Linear Amplifier HV Safety Interlock PCB 82 0300 04 Copyright 2004 CBTricks com All Rights Reserved Rev 1 0 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 5 5 6 PCB Trace Layouts 810 00 0 c8 PRIDE DX300 Bi Linear Amplifier HIGH Voltage Power Supply PCB 82 0300 01B Copyright 2004 CBTricks com All Rights Reserved Rev 1 0 82 0300 02B PRIDE DX300 Bi Linear Amplifier LOW Voltage Power Supply PCB 82 0300 02B Copyright 2004 CBTricks com All Rights Reserved Rev 1 0 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 5 PCB Trace Layouts Cont PRIDE DX300 Bi Linear Amplifier RF Relay and Control PCB 82 0300 03 Copyright 2004 CBTricks com All Rights Reserved Rev amp 1 0 32 Copyright 2004 CBTricks com CHAPTER 5 Pride DX300 5 7 Chassis Layouts Front and Rear QBQKEOSOBQGQEOSOS DSL 2000000 DDC CR OORO O STANDBY PL1 st FUSE 10A 3AG RECEIVE ON HIGH OPERATE o LOW TUNE O O O QO O O O O O O O O O O O O PLATE LOADING OOO OO OOO OO OOO OO OOO OO OOO OO OOO OO OOO OO OOO OO BIAS ADJ METERING PL4 PRIDE DX 300 Bi Linear Amplifier OUTPUT Pride Electronics San Diego Calif S N POWER ON FRONT VIEW 2 la e e z 100 RF POWER
25. le should be as short as is practical preferable less than five feet 3 Connect antenna or suitable high power dummy load to the output connector of the amplifier using RG8 U coax The smaller RG58 U coax may be used with matched antenna systems better than 1 5 to 1 SWR but will have somewhat higher loss The amplifier will match most loads from 25 to 100ohm 4 Exciter power levels above 12 watts PEP or 5 watts carrier level should be avoided as over drive of the amplifier will occur 5 The unit should be grounded for R F by attaching a ground strap of coaxial shield or 10 12 gauge wire to the ground post on the amplifier This should be connected by a short run to a ground rod or cold water pipe The idea is to have a short direct earth ground to keep the chassis at radio frequency ground In many cases normal operation can be had without such a ground but a good ground can help prevent television interference and make tuning straightforward 6 The A C line cord should be plugged into a three wire outlet The electrical circuit should be capable of handling a 10 ampere load Pride Electronics San Diego Calif S H Figure 2 0 Rear Panel 32 Copyright 2004 CBTricks com Pride DX 300 CHAPTER 2 RF POWER OUTPUT 100 300 500 o PRIDE DX 300 Bi Linear Amplifier Figure 2 1 Front Panel 2 1 OPERATION 1 Check to see that the TUNE STANDBY OPERATE switch is in the center or STANDBY position Apply power to the unit b
26. ny band Frequency Coverage 3 5 to 4 0 MHz 7 0 to 7 3 MHz 14 0 to 14 35 MHz 21 0 to 21 45 MHz 28 0 to 29 70 MHz Device Complement 1 4CX250B ceramic metal tetrode 1 2N2905 receiver preamp transistor 1 2N2905 RF switching transistor 24 1N4007 rectifier diodes 5 1N4001 rectifier diodes 3 1N914 small signal diodes Metering Functions Meter reads RF power output Amplifier tube screen current is monitored by an LED indicator Receive amplifier and power amplifier status are also monitored by LED indicators Front Panel Functions Power On Off switch Receive preamp on off switch SSB delay on off switch Tune Standby Operate switch Plate tuning control Band selector switch Plate Loading control Rear panel Functions Bias adjustment pot Metering Jack and Input Output RF connections AC Power Requirements 120VAC 60 Hz 500watts average 1000watts absolute peak Dimensions 12 wide x 9 high x 12 deep Weight 29lbs 32 Copyright 2004 CBTricks com Pride DX 300 CHAPTER 2 2 0 INSTALLATION 1 Select a location for your amplifier RF amplifiers need ventilation so choose a location that will not restrict the air flow around the amp and where it won t get water coffee or soft drinks spilled on or in it 2 Connect a short length of coaxial cable from the exciter to the amplifier input connector RG58 U or RG8 U may be used and a PL 259 connector is required at the amplifier end of the cable This cab
27. o M1 Meter 1ma F S With Special Scale 49 0300 00 6 7 CHASSIS Ref Description MFR Part No C1 Capacitor Ceramic Disk 0 01uF 1KV 08 0103 02 C2 Capacitor Ceramic Disk 0 01uF 1KV 08 0103 02 C35 Capacitor Ceramic Disk 0 001uF 1KV Across LED4 08 0102 00 C44 Capacitor Ceramic Disk 0 01uF 1KV 08 0103 02 C45 Capacitor Ceramic Disk 0 01uF 1KV 08 0103 02 C46 Capacitor Ceramic Disk 0 01uF 1KV 08 0103 02 C47 Capacitor Ceramic Disk 0 01uF 1KV 08 0103 02 C48 Capacitor Ceramic Disk 0 01uF 1KV 08 0103 02 C49 Capacitor Ceramic Disk 0 01uF 1KV 08 0103 02 C62 Capacitor Ceramic Disk 0 01uF 1KV 08 0103 02 C63 Capacitor Dipped Mica 360pF 1KV 21 1361 01 C64 Capacitor Dipped Mica 360pF 1KV 21 1361 01 C65 ASSY CAPACITOR 165pF TEFLON DIELECTRIC 01 0300 13 Teflon Sheet 4 50 X 3 50 85 0300 04 Teflon Plug 1 0 DIA 85 0300 05 Brass Sheet 4 00 X 3 00 85 0300 06 Teflon Sheet 2 00 X 2 00 85 0300 07 Brass Sheet 1 40 X 1 40 85 0300 08 C66 Capacitor Variable Panel 10 110pF 3KV 20 1101 03 C67 Capacitor Variable Panel 1350pF 750V 450pF x 3 20 2450 00 C68 Capacitor Ceramic Disk 0 0022uF 7 5KV 08 0222 07 C69 Capacitor Ceramic Disk 0 001uF 1KV Across LED3 08 0102 00 C70 Capacitor Ceramic Disk 0 01uF 1KV 08 0103 02 Ref Description MFR Part No S1 Switch SPST IOA 40 8006 00 S2 Switch 3A SPST 40 1606 00 S3 Switch 3A SPST 40 1606 00 S4 Switch DPDT Center Off 10A 40 8706 00 S5 Switch Band Ceramic 2 Wafer 5 Position 40 9002 00 Coupler Shaft 26
28. or Carbon Film 470K Ohm 1 2W 06 4704 00 R28 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R29 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R30 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R31 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R32 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R33 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R34 Resistor Carbon Film 470K Ohm 1 2W 06 4704 00 R35 Resistor Carbon Film 150 Ohm 1 2W 10 06 1501 00 R36 Resistor Carbon 30 Ohm 1 2W 5 06 0301 00 R37 Resistor Wire wound 20K Ohm 10W 17 2003 10 R38 Resistor Wire wound 12K Ohm 10W 10 17 1203 10 R39 Resistor Wire wound 10K Ohm 10W 10 17 1003 10 R40 Resistor Carbon 3 3K Ohm 2W 5 06 3302 02 R41 Resistor Carbon 3 3K Ohm 2W 5 06 3302 02 R42 Resistor Carbon Film 680 Ohm 1 2W 5 06 6801 00 Capacitors Ref Description MFR Part No C25 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C26 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C27 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C28 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C29 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C30 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C31 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C32 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C33 Capacitor Electrolytic 400F 450V 23 0406 45 C34 Capacitor Electrolytic 400F 450V 23 0406 45 C36 Capacitor Electrolytic 1000uF 25V 22 0108 00 C37 Capacitor Electrolytic 1000uF 25V 22 0108 00 Diodes Ref Des
29. or Ge They will withstand more abuse than the original 2 Watt rated parts DO NOT USE WIRE WOUND RESISTORS Period Mouser Electronics Westgate Labs and RF Parts sell this resistor Parasitic Suppressor ASSY 32 Copyright O 2004 CBTricks com 32 Copyright 2004 CBTricks com Pride DX300 8 6 Blower Detail CHAPTER 8 HOWARD INDUSTRIES PART NUMBER FOR THE BLOWER 3 20 1250 think this translates to 3 inch wheel 20 CFM at 1250 rpm RF Parts has this Blower 87 1250 for 39 95 8 7 Repair Part Suppliers RF Parts Company 435 South Pacific Street San Marcos CA 92078 http www rfparts com Orders and Information 800 737 2787 760 744 0700 7 00 a m to 4 00 p m PST Mon Fri Technical Help and Customer Service 760 744 0750 10 00 a m to 4 00 p m PST Mon Fri Tech Help is NOT available through the 800 line Fax 888 744 1943 760 744 1943 WESTGATE LABORATORIES L L C 1859 Caravan Trail Suite 106 Jacksonville FL 32216 http www westgateparts com 1 800 213 4563 Local 904 997 2031 Fax 904 997 2041 Email WestgateParts aol com Surplus Sales of Nebraska 1502 Jones Street Omaha NE 68102 3112 http Awww surplussales com Toll free 800 244 4567 Local 402 346 4750 Fax 402 346 2939 e mail grinnell surplussales com Mouser Electronics Inc 1000 North Main Street Mansfield Texas 76063 http www mouser com 800 346 6873 Local 817 804 3888 Fax 817 8
30. ot be able to follow the signal If a monitor scope is available it can be seen that the peak power is considerably better than the 400 watts or so that was obtained during tune up The SCREEN indicator will flicker with the transmission level and will reach full brilliance at high peak power levels This is a faster indicator of peak drive conditions than is the power output meter 10 For CW operation tune up as in step nine above Power output will be nominal 250 watts for 5 watts of driving power The SSB delay switch may be left in the on position to prevent relay chatter during keying 11 The 4CX 250B transmitting tube has been proven is commercial and military uses where long life and reliability are major factors Although it is designed to work a little harder in amateur service it will still be extremely reliable if a few common sense rules are applied a Make sure that the tube always receives a good airflow Remember that a lot of watts are being packed into that rather small package and that the only way to keep it cool is to get air through the tube fins Do not block the top of the cabinet or stack other equipment on the amplifier Make sure that the rear of the chassis where the blower gets its air is open to cool room air If the bottom cover of the unit has to be removed for service see that it is replaced properly prior to plugging in the unit for safety also The bottom chassis must be pressurized in order to force air thr
31. ough the tube fins b Wait 60 seconds before applying drive to the tube Allowing the tube to properly warm up will help you get the longest service from it c After a long period on the air let the amplifier run in the STANDBY mode for a minute or so before turning off the power switch This allows the blower to bring the tube down to a cooler temperature fairly rapidly d Avoid excessive R F drive to the amplifier e Use care in tuning most tube failures are the result of operator error not equipment failure These transmitting tubes are used for thousands of hours in commercial service and similar results should be yours with reasonable precautions 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 3 3 0 Circuit Description The DX 300 power amplifier uses a 4CX 250B Tetrode ceramic metal construction and utilizes forced air cooling It is in a grounded cathode driven grid configuration that provides very high power gain high peak power output and excellent linearity and harmonic suppression The use of tuned input circuits and broadband matching transformers permits low drive operation combined with additional rejection of exciter harmonics Class AB operation of the tube permits high peak powers with low distortion products and harmonics The amplifier has a tune function that restricts the power gain of the amplifier for easy safe tune ups The use of a single tube in the design avoids the problem of matching tubes an
32. r a radio that doesn t have one built in And it helps to reduce the heat load on the tube from the carrier power 7 6 Bias Circuit Modification Version 2 Another way is to use a transistor and zener The following uses two TIP50 s you can use one transistor as long as the one you use can handle the current and voltage Every shop has a pile TIP50 s laying around and they are cheap You can use the stock D25 for the zener or series as many lower voltage 1W zeners you need to get the voltage range you like TIP50 TIP50 Ene Remove 1N5375 ur 82V 5W LOW Voltage RV1 Power Supply PCB 800 54 BIAS CBTricks com A Copyright 2004 All Rights Reserved 1 Rev 1 2 Cut Center Mount on back wall Pin C of the chassis Figure 7 2 Transistor Zener Bias Mod 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 8 8 0 Introduction In this section have information on some of the components use in the DX300 8 1 Antenna Change Over and Preamp Relay Information The antenna change over relay RL1 is a 4 pole double throw 4PDT relay with 10 amp contacts and a 12 volt 185ohm coil I ve always seen an Allied Control relay here Part number TY154 CC CC 12VDC The current part number to order would be TY154 4C 12VDC with only change being the way the C s are entered Potter amp Brumfield have a similar relay with contacts rated at only 7 5 amps but it would probably work in a pinch Th
33. s 10 Windings 01 0300 22 Resistors Ref Description MFR Part No R44 Resistor Carbon 1 5K Ohm 2W 10 06 1502 02 R45 Resistor Carbon 1 5K Ohm 2W 10 06 1502 02 R46 Resistor Carbon 18K Ohm 2W 10 06 1803 02 R47 Resistor Carbon 18K Ohm 2W 10 06 1803 02 R48 Resistor Carbon 270 Ohm 2W 10 06 2701 02 R49 Resistor Carbon 270 Ohm 2W 10 06 2701 02 R50 Resistor Carbon Film 1K Ohm 1W 06 1002 01 R51 Resistor Carbon Film 470 Ohm 1 2W 5 06 4701 00 R52 Resistor Carbon Film 680 Ohm 1 2W 5 06 6801 00 R53 Resistor Carbon Film 680 Ohm 1 2W 5 06 6801 00 R54 Resistor Carbon Film 10K Ohm 1 2W 5 06 1003 00 R55 Resistor Carbon Film 270 Ohm 1 2W 5 06 2701 00 R56 Resistor Carbon Film 470 Ohm 1 2W 5 06 4701 00 R57 Resistor Carbon Film 68K Ohm 1 2W 5 06 6803 00 R58 Resistor Carbon Film 1K Ohm 1 2W 5 06 1002 00 Capacitors Ref Description MFR Part No C39 Capacitor Ceramic Disk 0 01uF 1KV 08 0103 02 C40 Capacitor Ceramic Disk 0 01uF 1KV 08 0103 02 C41 Capacitor Dipped Mica 39pF 5 DM15 21 1390 00 C42 Capacitor Dipped Mica 10pF 5 DM15 21 1100 00 C43 Capacitor Ceramic Disk 0 01 uF 1KV 08 0103 02 C50 Capacitor Ceramic Disk 0 01uF 50V 05 0103 00 C51 Capacitor Electrolytic 35uF 25V Axial 22 0356 00 C52 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 C53 Capacitor Dipped Mica 120pF 5 DM15 21 1121 00 C54 Capacitor Dipped Mica 50pF 5 DM15 21 1500 00 C55 Capacitor Ceramic Disk 0 001uF 1KV 08 0102 00 Diodes Ref Description M
34. through the relay to the output connector In the operate or tune mode drive is switched to the 9 1 input matching transformer T3 which steps the impedance up from 50ohm to 450ohm to feed the input circuitry The rear deck of the Band Switch selects a tuned circuit for the appropriate band Two 15000hm 2W resistors R44 R45 are in parallel with the resonant input circuit to provide proper loading and bandwidth Adjustable bias voltage is fed to the grid through a 200uH choke L14 an input toroid and the parasitic choke Z1 on the tube grid connection v1 4CX250B RF INPUT 15 METER E 10 METERS 1500 2 Low Voltage Supply PCE 82 0300 02B 1500 2 L14 Figure 3 4 RF Input Circuit 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 3 Another set of contacts on the RL1 4PDT relay switches the cathode circuit of the tube to ground when the amplifier goes into the on the air condition When not transmitting two 18K 2W resistors R46 R47 provide a cathode blocking bias that prevents the tube from pulling current The two 2700hm 2W resistors R48 R49 that are in series with the cathode line provide some additional bias during the TUNE mode causing a loss in power gain and making it easy to tune up at lower power These resistors are shorted out by a section of the TUNE STANDBY OPERATE switch when in the OPERATE mode y1 CR EE EEE EEE RF Input and Control PCB 4CX250B 52 0300 03 C46 C49 OF 1KV C46
35. urrent The 350VDC is fed through two power resistors to provide source current for an 82 volt Zener diode D25 that provides a stable bias supply voltage This 82 volt supply is dropped in a voltage divider consisting of the back panel bias pot and two 33000hm 2W resistors R40 R41 to provide an adjustable stable bias source for the tube control grid D17 D24 1N4007 R27 R34 470K 1 24 C25 C32 O01pF 1KY SCREEN 340YDC SCREEN BIAS 62VDC MAX 82 0300 02B LOW VOLTAGE POWER SUPPLY PCB R40 R41 3300 3300 2 2 Figure 3 2 Screen and Bias Voltage Power Supply 3 3 Low Voltage Supply PCB This supply consists of a full wave voltage doubler which is supplied from the 6 3volt filament winding on the smaller transformer 12 to 15 VDC is developed for use of the receive preamp relays and indicators 82 0300 02B LOW VOLTAGE POWER SUPPLY PCB Figure 3 3 Low Voltage Power Supply 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 3 3 4 R F Input and Control Board This board is located under chassis near the tube socket and is mounted horizontally It contains the R F switching circuitry input matching transformer and tuned toroid input coils the receiver preamp and some of the control circuitry Control Drive power from the exciter is fed to one set of contacts on the RL1 4PDT relay and coupled also to a 2N2905 Q1 relay switching transistor When the amplifier is in the standby mode drive is fed
36. ust it with the top removed but use caution If adjustment becomes necessary it should be performed only if the following equipment is available Exciter 100 to 200watts output at 28 MHz Dummy load 50ohm with an accurately calibrated wattmeter Calibration procedure 1 Remove the top cover after allowing several minutes for the unit to discharge to a safe level 2 Disconnect the right hand as viewed from the front of the unit coax cable at the wattmeter board and attach a short length of RG58 U coax cable from the wattmeter board to the output of your exciter 3 Disconnect the left hand coax cable and attach a short length of RG58 U from the wattmeter board to the input of the dummy load wattmeter 4 Apply power and adjust the exciter for an output of 100 to 200watts as read on the dummy load wattmeter 5 Set the potentiometer on the wattmeter board for the same reading This now completes the calibration of the wattmeter Restore the unit to its original configuration 4 3 Input SWR adjustment If the input SWR should require adjustment on any particular band the following procedure should be used 1 Remove the bottom cover after allowing sufficient time for the power supply to discharge to a safe level 2 Apply 12 VDC to point B as identified on the pictorial of the main circuit board O can 16 L14 e R48 e C43 15 MG L OB e L2 IT gt Hin Figure 4 3 Jumper B 3 Place the TUNE STANDBY OPERATE sw
37. y PCB 82 0300 02B Copyright 2004 CBTricks com All Rights Reserved Rev 1 0 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 5 5 1 High Voltage Supply PCB Board 1 R21 ciem cu Jr en D10 D11 TI JF c1 C18 R22 o a 4 cmi D14 ins 8 Rie S D 85 10 C21 TO E on 85 0300 0LB 2 R13 9 s C15 e Dye C14 C22 pr pe 7 ot a o e010 5 R21 B d QE C16 ew Ss CR et og Dy fc 8 Tes C23 9 e e Di4y 4 gt R22 R19 D1 25 C21 C20 PRIDE DX300 Bi Linear Amplifier HIGH Voltage Power Supply PCB Board 1 82 0300 01B Copyright 2004 CBTricks com All Rights Reserved Rev 1 0 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 5 5 2 High Voltage Supply PCB Board 2 85 0300 0LB PRIDE DX300 Bi Linear Amplifier HIGH Voltage Power Supply PCB Board 2 82 0300 01B Copyright 2004 CBTricks com All Rights Reserved Rev 1 0 32 Copyright 2004 CBTricks com Pride DX300 CHAPTER 5 5 3 Wattmeter PCB Component Side View PRIDE DX300 Bi Linear Amplifier Meter PC 82 0300 02B Copyright 2004 CBTricks com All Rights Reserved Copper Side View Rev 1 1 32 Copyright 2004 CBTricks com Pride DX300 5 4 RF Input and Control PCB e2 18441344 15 12 de 9 6 10875 CHAPTER 5 PRIDE DX300 Bi Linear Amplifier RF Relay and Control PCB 82 0300 03 Copyright 2004 CBTricks com Al
38. y switching the POWER switch to the ON position You will hear the cooling blower come up to speed Wait 60 seconds for the tube to come up to operating temperature 2 During the time that the amplifier is warming up or at any time that the TUNE STANDBY OPERATE switch is in the STANDBY position the exciter may be operated normally straight through the amplifier 3 Set the band switch to the same band as that the exciter is tuned to 4 After warm up place the TUNE STANDBY OPERATE switch into the TUNE position The OPERATE indicator will light up indicating that the unit is ready for operation If the RECEIVE switch is on the RECEIVE indicator will light also indicating operation of the receive preamplifier 5 Rotate the PLATE LOADING control to the nine o clock counter clockwise position 6 Apply several watts of drive from the exciter and quickly peak the PLATE TUNE control for maximum output as indicated on the front panel wattmeter The SCREEN overload indicator may glow at this time and will peak in brilliance at approximately the same place of tuning that maximum output occurs 7 The PLATE LOADING control is then turned clockwise 1 2 division or so and the PLATE TUNING control is peaked again for maximum output The brilliance of the SCREEN indicator will peak again but not quite as brightly as before This process is continued until a further increase in the PLATE LOADING control will give no further increase in power output
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