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President Washington d858

Discussion in 'General CB Services Discussion' started by kaos513, Aug 10, 2021.

  1. nomadradio

    nomadradio Analog Retentive

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    Nobody has asked if the sideband receive works as it should. If not, trouble with the carrier crystals is possible.

    Does sideband transmit work at all?

    If the lights dim and the relay drops out immediately, pull the power cord immediately and clip out that tiny tantalum cap C179.

    Before you damage the relay. A hard one to find when you need one.

    73


     
    midnight special likes this.

  2. NZ8N

    NZ8N Well-Known Member

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    Washington 858 bad Tantalum cap.jpg
    Washington 858 bad Tantalum cap location.jpg

    If this capacitor is shorted, it will shut down your transmit in all modes, and show a high current draw on the power supply in transmit mode.
     
    tecnicoloco likes this.
  3. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    This thing hasn't bee nrecapped has it?

    Don't see any foil rework around those caps - you @kaos513 - should know better! :)
     
  4. OldTech03

    OldTech03 Sr. Member

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    You say it tests fine but do you see the frequencies being
    Actually, I did ask if the SSB Power was working but I don't know if he ever responded to that question?
     
  5. kaos513

    kaos513 Sr. Member

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    I have no ssb power as well
     
  6. kaos513

    kaos513 Sr. Member

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    I recapped the radio made sure didn’t put any caps backwards as for tantlums as well
     
  7. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Then you know that you have to do - continuity checks.

    Test points - like TP2 and 4 - that are in NZ8N's post as well as testing Collector of Driver and Final to AM Regulator - show continuity? Gotta use that Relay to check - so be careful.

    Voltage checks ...

    JP35 - show 8V in TX?

    You may have a TX light, does you no good if it can't send power to the TX Strip...

    Mode switch - blown? <<< Biggest culprit - 36 watts equates to 3 amp pull from somewhere...

    AM Regulator even putting out a voltage?

    When you don't even have SSB, then look at your power branches off the power switch.

    Signal Checks - like OT-03 asked - anything at the Mixer?

    You said you recapped, that's great, but do both IF's that radio uses, getting to the TX?

    If 3 amps are routing thru, somewhere on the board, it's getting hot. Relay stuck?
     
  8. OldTech03

    OldTech03 Sr. Member

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    I must confess I sometimes post without that little voice in the back of my head that keeps telling me don't assume that voltage testing is part of the routine don't ever assume that frequency testing with either a scope or frequency counter is part of the routine, so for the record, the first thing all would-be repairmen should have is a decent DVM and it helps to use it. Now if you don't have a good frequency counter designed for component level troubleshooting you are left with not being able to look at oscillator and mixer stages to see if they are actually working and producing an end result that would translate to 27 meg signal being delivered to the first buffer/pre-driver stages. Here is the thing if indeed there is a bad electrolytic that isn't being used in a feed-thru for audio then it must be used for some kind of voltage stabilization so if that cap is shorted you need to know. Sometimes "a lot" I forget the powerful nature of basics when I taught troubleshooting to young tech students there was always set rules that were taught that admittedly revolved around some knowledge of block diagrams they are a powerful weapon in troubleshooting because it's a roadmap to what modules or sections of the radios circuits and their relationship to each other or at least that there is a relationship.
    I guess the short of this is read, learn, and follow basic troubleshooting procedures. Now if you say I don't know what that is there are many books that could be found that will guide you through that process.

    Oh and don't forget an OSCILLOSCOPE you can get some pretty nice scopes real cheap It is my go-to piece of equipment and the Rigol low-end scopes will also display the frequency and amplitude of that frequency I use this little devil nearly every day.

    https://www.thriftbooks.com/w/cb-ra...0aAmUfEALw_wcB#idiq=21778179&edition=17326669

    https://www.ebay.com/itm/1145353091...mJ0SaAZfVwWQXqp35kKEfJ92fAwiqSSMaAjiWEALw_wcB

    THIS BOOK COVERS ALL THE BELOW The best $65 you will ever spend if you are serious about learning:

    http://www.cbcintl.com/urbook.htm


    CHAPTER 1 — INTRODUCTION TO CB SERVICING
    The new Surface Mount technology. CB technical specs defined. Test equipment you’ll need. Inexpensive testing aids you can build yourself. Additional information sources. Includes a complete shopping section for CB radios, antennas, parts, accessories, and test equipment including names, addresses, and "800" numbers. Plus much more!

    CHAPTER 2 — BASIC TROUBLESHOOTING TECHNIQUES
    Block diagrams teach you the theory of AM and FM receivers and transmitters. Use of the systematic approach. Testing semiconductors. Signal injection and signal tracing. Intermittents. Interpreting DC biases. Transistor amplifier circuits. Understanding device markings. Plus much more!

    CHAPTER 3 — GENERATING THE SIGNAL FREQUENCIES
    Crystals and crystal oscillators. Series and parallel resonance. The Colpitts Oscillator. Overtone oscillators. Oscillator troubleshooting. How to order crystals. Walkie-Talkies. The VFO, Crystal, and PLL synthesizers. Elements of the PLL system. How digital dividers work. Generating the binary and BCD channel codes. ROM programming. Additional PLL functions. Expanded coverage synthesizer methods. Broadbanding methods. Evolution of the PLL using several examples. PLL alignment procedures and equipment set-up. PLL troubleshooting methods. The MB8719 synthesizer. Includes 23-channel crystal mixing charts covering 90% of all AM CB's; use these to quickly determine dead channels or 10-Meter Ham conversions. Plus much more!


    CHAPTER 4 — RECEIVER CIRCUITS
    RF and IF Amplifiers. Mixers. Single- vs. dual-conversion methods. IF selectivity methods plus tips on improving them. IF troubleshooting. Detector circuits. ANL circuits. AGC circuits. AGC troubleshooting. The S-Meter circuit. Noise Blankers. NB troubleshooting. FM detector circuits. FM receiver troubleshooting. Squelch circuits. Squelch troubleshooting. Scanning circuits. Selective calling. The audio amplifiers. Audio troubleshooting. LED channel displays and bar/graph displays. Delta Tune circuits. Tone controls. Receiver alignment procedures and equipment set-up. Plus much more!

    CHAPTER 5 — TRANSMITTER CIRCUITS
    The RF amplifier chain. Oscillators, mixers, and buffer stages. Power amplifiers. Classes of amplifier operation. Biasing methods. Vacuum tube power amps. Power doubling methods. Power reduction methods. Coupling and filtering. AM and FM modulation methods. Speech processing. Mikes and microphone problems. Limiters and compressors. Measuring and adjusting modulation. RF Power Meter circuit. Modulation meter circuit. SWR Meter circuit. Antenna Warning circuit. Roger Beep Oscillator circuit. CW keying circuit. Selective calling circuit. Transmitter alignment procedures and equipment setup. Plus much more!


    CHAPTER 6 — SINGLE-SIDEBAND CIRCUITS
    SSB characteristics, pros, and cons. SSB signal generation. The Carrier Oscillator. Carrier and synthesizer offset methods. The speech amplifier. The Balanced Modulator. BM troubleshooting. Sideband selection methods. SSB crystal filters. The mixer. Mixer troubleshooting. Linear RF power amplifiers. Biasing methods. AM/SSB power and modulation control. ALC. Testing the SSB transmitter. SSB reception methods. The Balanced Demodulator. The Product Detector. The Clarifier circuit. Clarifier troubleshooting. IF amplifiers. SSB AGC methods. SSB transceiver alignment procedures and equipment set-up. Plus much more!


    CHAPTER 7 — POWER SUPPLIES AND T/R SWITCHING
    The mobile DC power supply. Ground loops. Electronic and relay T/R switching circuits. Voltage regulation circuits. The base station AC/DC power supply. The solid-state base supply. Tube and hybrid power supplies. DC-to-DC power supplies. Multimode transceiver power supplies. Includes use of SAMS Fotofacts schematics for step-by-step analysis of several common power circuits. Troubleshooting the power supply. Plus much more!

    CHAPTER 8 — ANTENNAS AND TRANSMISSION LINES
    Mobile antenna types and mounting hardware. 27 MHz characteristics. The ½-wave antenna. Reactance and tuning. Impedance and radiation resistance. The Standing Wave Ratio (SWR). Coax length vs. SWR. Coax characteristics. Effect of in-line accessories. Coax losses vs. SWR losses. Some practical coax tips. Bandwidth. Gain and directivity. Radiation patterns and field strength. Omnidirectional antennas. Loading coils. Directional mobile antennas. The Quad and Yagi beam, including dimensions for home construction. The PDL. Antenna matching principles. Tuning and troubleshooting the mobile whip. Magnetic antennas. Co-phasing simplified. Co-phase matching tips. Use of dummy loads in troubleshooting. Matching high-Z verticals. Matching Quad and Yagi beams. Stacking beams for increased gain. Preventing TVI. Matching special CB antenna types. Plus much more!

    APPENDIX A — SOLVING NOISE AND INTERFERENCE PROBLEMS
    TVI and RFI. Front-end overload. Audio interference. Ignition and other automotive noise problems. Includes reference data and parts suppliers.

    APPENDIX B — FCC FREQUENCY CHART
    Quick reference 40-Channel frequency listings including tolerances.

    Before I end I just want to make sure nobody thinks I'm trashing anyone or trying to put myself on some kind of genius pedestal or looking down at you across my giant nose of indignation no, no, no I just feel all beginners would have a much better time and sense of accomplishment in the hobby if they invested time in the lost art of READING!... and it can be really rewarding to realize you now understand or have a better understanding how circuits work and how they interact.

    And this is just a shortlist of possible technical information available. So, That is all I have to say about that !!!
     
    #23 OldTech03, Aug 11, 2021
    Last edited: Aug 11, 2021
  9. kaos513

    kaos513 Sr. Member

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    Relay is not stuck I can see it move back and forth when I key up
     
  10. kaos513

    kaos513 Sr. Member

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    I have fixed several radios in the past this is the first one I ever encounter with a relay and oldest model I worked on, radio has great receive as I aligned it my self
     
  11. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Again I ask was there any mods done?

    Mic plug, External Speaker - Talkback mods - scorch marks - Crayola's by power supply to match the color of the wires it's now melting onto...you show us a foil side - but not the top - so what do you want us to do? We're guessing and by your responses - it's raising a few questions from the rest of us - if you're really paying attention or just just want to play...

    You've fixed these things before - why are you having such a problem with one using a relay?

    You can wiggle a relay - but does it make contact?

    Continuity checks - gotta see if you have any wires, traces, jumpers - acting like blown fuses.
    • You shold also be looking at your work with the caps - see if your work is causing a dead short on the TX line pulling those amps?
    You may get a TX, but that is from a "ok to go".

    No carrier - no ssb - no-nothing - yet you see 36 WATTS of power draw. Ok, lets do some math...

    36 watts = assume 12V X ?

    Or
    ? = 36 / 12

    Roughly 3 amps of draw down in the board - but no power -

    Lift COLLECTOR leg of Driver - still 36 watts?

    Lift COLLECTOR leg of Final - still 36 watts?

    Short somewhere...

    Where ever the 36 watts dropped - is the part you need to check - thinking Driver and Final - one or other or both are shorted causing draw

    Only you need to test for that.
     
    #26 Handy Andy, Aug 11, 2021
    Last edited: Aug 11, 2021
    Holydvr likes this.
  12. kaos513

    kaos513 Sr. Member

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    Tr 25 regulator reads the following B=13.00 Vdc Emmiter = 11.00 vdc Collector 11.00 vdc
     
  13. KneeBiter

    KneeBiter Well-Known Member

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    I'm going to ignore all the advice and not respond and keep telling you what I find !!
     
  14. kaos513

    kaos513 Sr. Member

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    Little progress made d25 was toasted replaced hear my audio on all modes very low but still not there yet
     
  15. kaos513

    kaos513 Sr. Member

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    Still no luck
     

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