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uniden washington

Discussion in 'General CB Services Discussion' started by kaos513, Dec 23, 2018.

  1. kaos513

    kaos513 Well-Known Member

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    found r104 clipped could that be my issue?


     

  2. Handy Andy

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

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    Then there ya go, looks like a wire routing or TR13 "Conversion" issue.

    Something is causing the leakage....

    So go back over some of those areas like around TR13, TR36 as well as their support parts. Volume control and speaker ground are pin 5 on that mic. The Mic amp itself also ties right to the audio amp - so the Mic amp strip and CB/PA as well as the PA amp (TR30) may all be accidentally left on due to D39 and D40 being blown open and not going to Pin 5 ground. Again check those diodes and look for carbon trails of burnt flux and bad solder in the mic amp section - including the PA/CB switch S404 - ALL THE POLES can have something going on that throws you for a loop.

    Many times I've seen someone sneak in a parts change that throws you for a loop because a part they swapped out was changed to offer some tailored improvement to one user that doesn't apply to the OEM.

    I have also had to go over radios that have flux dated back into the original assembly and this is where you may have a problem or two in leakage and "crosstalk" issues. The cap soldered in to straddle one sections' bias to another - can also leak across a poorly soldered and flummoxed (flux drop) set of pads generating a similar problem to what you have. Remember the work done by the speaker switching branches can add to this because the chassis may have speaker audio applied to it and it's now propagating a signal throughout the entire chassis.

    Galaxy radios in their AM and FM as well as SSB separations - all had routing problems if too much solder or extra flux was left behind. The carbon trail left enough of a resistive circuit to cause crosstalk and strange AGC to RF meter readings you did not expect only to find that cleaning up the AM detector section in the early 3600XX EPT board - took care of such issues.
     
    Shadetree Mechanic likes this.
  3. Handy Andy

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

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    Could be more of an AMC issue - that is an AMC amp that "samples" the AM power and carrier - part of the resistor divider network for the Base bias of that AMC amp - but it can also mean they tried defeating limiter works too. so brace for even more discoveries...
    Kaos513.jpg
     
    #108 Handy Andy, Jan 6, 2019
    Last edited: Jan 6, 2019
    Shadetree Mechanic likes this.
  4. kaos513

    kaos513 Well-Known Member

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    Did an alignment I lost my signal generator tone today I tried generator on another radio works good
     
  5. OldTech03

    OldTech03 Sr. Member

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    Well, are you trying to find it?
     
  6. kaos513

    kaos513 Well-Known Member

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    Yes working on it
     
  7. kaos513

    kaos513 Well-Known Member

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    Strange it's right on frequency but do no get tone
     
  8. Handy Andy

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

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    Audio amp ok?

    Tr36 pre-amp ok?

    Squelch control ok?

    Are you ok?
     
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  9. OldTech03

    OldTech03 Sr. Member

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    No Andy he is not Ok. He is out of TONE!
     
  10. kaos513

    kaos513 Well-Known Member

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    Rf gain is not ok, squelch is ok tr-36 not known yet
     
  11. Handy Andy

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

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    Gosh Darn It!

    I've been out of TONE for a long time - just ask my wife...

    Shoot! And I just gave the last of my Left-Turn Blinker Fluid to a neighbor.
     
  12. kaos513

    kaos513 Well-Known Member

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    Tr-36 is good
     
  13. Handy Andy

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

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    Do you have PA though?

    I mean, you're checking to make sure the Audio amp is...amping...?

    Because losing tone can mean that what you heard as "volume doesn't go all the way down. May have been TR13 audio amp up at the conversion section - heading into self-destruct full-throttle.

    It' is why I mentioned to check it to make sure it is not.

    When I mention to check the transistor - that usually means in circuit - if TR13 is causing this the transistors' voltage readings would be out of specs.
    Look for old caps...
    Cobr142WashingtonTR13.JPG
    If they went shorted - can bias TR13 into self destruct.

    Now as far as the audio amp - if it's failing it's internal - but you will need to review and check all the Electrolytic caps around the audio chip - for if a bootstrap, ripple filter or EQ is not isolating each section of the amp (READ:Those pins) from DC- the amp biases itself into self destruct. This happens a lot on older radios the output cap will short and 1/2 the supply rail usually goes with it. BOOM.
     
    #118 Handy Andy, Jan 14, 2019
    Last edited: Jan 14, 2019
    kaos513 and Robb like this.
  14. kaos513

    kaos513 Well-Known Member

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    r101 was shorted replaced it did the alignment but volume will not cut off still
     
  15. Handy Andy

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

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    So you found tone?
     

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