Question about Uniden PRO510XL 40-Channels Base CB Radio

1 Answer

Uniden Pro 510xl can send but not receive

A friend and I each have a Uniden pro 510xl CB radio in our trucks. His radio will transmit (I can hear his messages) but will not receive (he can not hear my messages). We tested both radios with others in the RV park and confirmed that it is HIS radio which has the problem.

I switched microphones in case switching in the microphone was permanently turning off the incoming amplifier, but no change. There is a hiss from the speaker, and touching a voltmeter to connections around the amplifier and speaker does produce clicks.

It's as if the incoming signal never makes it to the audio amplifier.

We looked for obvious cold solder joints, no luck.

Any suggestions please?

Ed

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  • 8 more comments 
  • whitetmp Dec 31, 2008

    Thanks tparsenault. Although I haven't tried an external speaker there is no doubt that the speaker is functional - we can get it to click, and it will play music when I feed it from a CD player. We already checked the solder joints around the pcb which feeds the microphone, but I'll check it again based on your comment that it's a common problem. Any other ideas would be appreciated.

    Ed

  • whitetmp Dec 31, 2008

    Thank you Tom. Dumb old me, I never thought to look at the receive signal. I'll check that tomorrow.



    Unfortunately, we're in Mexico for the winter, and in a remote area, so access to a signal generator is not an option.



    Are you able to describe where the audio pin is ?



    Thanks

    Ed

  • whitetmp Dec 31, 2008

    Tom, we have eliminated the antenna as a problem by switching the radios and antennas. I didn't mention earlier that we have a third friend here with the same radio and antenna so we've tested the antenna and microphone on his radio. We're certain that the problem is somewhere in the radio itself.



    Thanks for the info re the location of the audio pin. I'll try your suggestions tomorrow and will let you know.



    Thanks again.

    Ed

  • Anonymous Jan 01, 2009

    Hi Tom

    Tried your suggestions this morning with the following results:

    1.
    When transmitting, the transmit signal shows on the LEDs on the front, but when receiving there are no indications that a signal is being received. No LEDs light up.
    2.
    I placed my finger across the contacts of the 3 chips on the board, one at a time:
    IC 302 is a small rectangular chip on the main board, positioned on its side, right behind the pcb which feeds the microphone
    IC301 is a flat rectangular chip in a normal “flat-on-the-board” position almost halfway back on the board
    IC1 is the audio amplifier attached the the metal housing
    I do not have access to a circuit diagram so I have no information on what IC302 and IC301 actually do.
    3.
    I checked again the solder connections on the pcb feeding the microphone and all seem to be intact.
    Does this additional information help identify the source of the problem??
    Thank you and Happy New Year, from Lo de Marcos, Mexico
    Ed

  • Anonymous Jan 01, 2009

    Jan 1/09

    Hi Tom

    Tried your suggestions this morning with the following results:

    1.
    When transmitting, the transmit signal shows on the LEDs on the front, but when receiving there are no indications that a signal is being received. No LEDs light up.
    2.
    I placed my finger across the contacts of the 3 chips on the board, one at a time:
    IC 302 is a small rectangular chip on the main board, positioned on its side, right behind the pcb which feeds the microphone
    IC301 is a flat rectangular chip in a normal “flat-on-the-board” position almost halfway back on the board
    IC1 is the audio amplifier attached the the metal housing
    I do not have access to a circuit diagram so I have no information on what IC302 and IC301 actually do.
    3.
    I checked again the solder connections on the pcb feeding the microphone and all seem to be intact.
    Does this additional information help identify the source of the problem??
    Thank you and Happy New Year, from Lo de Marcos, Mexico
    Ed

  • whitetmp Jan 01, 2009

    Jan 1/09



    Hi Tom



    I tried your suggestions this morning, with the following results:



    1.

    When transmitting, the transmit signal shows on the LEDs on the front, but when receiving there are no indications that a signal is being received. No LEDs light up.

    2.

    I placed my finger across the contacts of the 3 chips on the board, one at a time:

    IC 302 is a small rectangular chip on the main board, positioned on its side, right behind the pcb which feeds the microphone

    IC301 is a flat rectangular chip in a normal “flat-on-the-board” position almost halfway back on the board

    IC1 is the audio amplifier attached the the metal housing

    I do not have access to a circuit diagram so I have no information on what IC302 and IC301 actually do.

    3.

    I checked again the solder connections on the pcb feeding the microphone and all seem to be intact.

    Does this additional information help identify the source of the problem??

    Thank you and Happy New Year, from Lo de Marcos, Mexico

    Ed

  • whitetmp Jan 01, 2009

    Jan 1/09



    Hi Tom



    Tried your suggestions this morning with the following results:



    1.

    When transmitting, the transmit signal shows on the LEDs on the front, but when receiving there are no indications that a signal is being received. No LEDs light up.

    2.

    I placed my finger across the contacts of the 3 chips on the board, one at a time:

    IC 302 is a small rectangular chip on the main board, positioned on its side, right behind the pcb which feeds the microphone

    IC301 is a flat rectangular chip in a normal “flat-on-the-board” position almost halfway back on the board

    IC1 is the audio amplifier attached the the metal housing

    I do not have access to a circuit diagram so I have no information on what IC302 and IC301 actually do.

    3.

    I checked again the solder connections on the pcb feeding the microphone and all seem to be intact.

    Does this additional information help identify the source of the problem??

    Thank you and Happy New Year, from Lo de Marcos, Mexico

    Ed

  • whitetmp Jan 01, 2009

    Hi Tom



    In answer to your question, even when Don is parked right next to me there is no receive signal showing on his radio.



    We had more or less reached the conclusion that the radio was a throwaway, but being in Mexico for the winter we had hoped to find a solution so that Don would have the radio working on the way back to the USA in March.



    Thanks for trying so hard to solve his problem. I'll let him know your recommendations re a replacement.



    Ed

  • Tom Arsenault
    Tom Arsenault May 11, 2010

    The only other thing I would ask is do you notice any recieve signal on the front? My be the rf gain or squelch crapped out. If you know where the audio pin is try holding a finger across the solder conections with the radio powered up and on if you get a squeal then we know the audio circut and speaker is working, might need to put a signal gen on it and trace the rx if all else fails;

    Good Luck,

    Tom

  • Tom Arsenault
    Tom Arsenault May 11, 2010

    Have you tried an external speaker? Checked around the mic connector at pcb? I have found this quite a bit on the 510 xl's.

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  • 170 Answers

If you look on the solder side of board you shoud see a straight line of 5-7 solder joints, look on the other side the audio vhjp is a bmack thin retangular ic chip. Not to worry you wont hurt anything by doing this. Its an old cb tech trick to test audio chips.GOOD LUCK.

Oh one other thing does the radio have same same problem in either vehicle? A insulating washer on the antenna bracket can cause this also,
Happy New Year , Tom

Posted on Dec 31, 2008

  • Tom Arsenault
    Tom Arsenault Jan 01, 2009

    IC 1 is the one to check but I don't think that's the problem. sounds like a detector circuit or one of the rx stages isn't working. I am not one to blow smoke up you know where, To properly troubleshoot this you need to have it on a bench, Even if your neighbor pulls right up next to you and keys up do you notice receive? I think its def a rx prob and probably will cost more to fix then replace. Back in the day we got 40 bucks for the 510 xl, Get a nice cobra 25 , 29 ltd or the uniden clone. Very dependable, inexpensive radios. Really popular with truck drivers, so most cb shops have experience and parts available.

    Sorry I couldn't help out more, please look me up next time you have a problem.

    Happy New Year,

    Tom (The tech formally known as double-t in the south east coast.)

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