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Trc 424 with tx mod coming out of the internal speaker.

Hi, I am working on a friends trc 424 that has a "talk back" problem. The radio transmits well with good modulation it just has this tx audio coming out of the internal speaker loud and clear problem. Where should I start to troubleshoot this problem?

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  • n2vww Nov 22, 2013

    I found the problem, It was an open diode.

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  • 141 Answers

Check for a resistor soldered across the P.A. jack and external speaker jack (solder side of the board) if you see one, remove it

Posted on Nov 26, 2013

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Posted on Jan 02, 2017

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SOURCE: Radio Shack TRC-502 cb radio

Here is the owners manual I'l see if I can get my hands on a internal schematic

http://support.radioshack.com/support_electronics/doc62/62220.pdf

Posted on May 14, 2008

  • 55 Answers

SOURCE: radio shack trc-502 cb radio

YOU CAN GET SCHEMATICS FOR THAT MODEL
I JUST LOOKED IT UP FOR YOU........THE BOOK IS SAMS PHOTO FACT...WEBSITE IS

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THEY HAVE EVERY CB RADIO EVERY MADE

GOOD LUCK

Posted on Feb 21, 2009

  • 773 Answers

SOURCE: Cobra 29LTD CHROME low tx no mod, rx good low Vol, talkback good

1 why would you change the finals?? Have you checked you antenna? How are your SWR's? Crappy antenna's cause a lot of problems.

Use an external meter to see what the SWR is, and see what the output is PEP. If its low, then there is something wrong. If it is High, change the mic and turn up the dynamic all the way.

Next. Have you been messing around in there?? Tryin to get more wattage? You turned VR4? If you thought you were turning it up by turning it all the way to the right, you turned it all the way down. Turn it all the way to the left.

Posted on Jun 17, 2009

Benimur
  • 6966 Answers

SOURCE: cobra 142 gtl no audio on receive

Hi and welcome to FixYa,

Initially, the speaker of course has been checked?

Offhand, would partial schematic of the mic and speaker section help?

7008f3b.jpg

Good luck and thank you for asking FixYa.

Posted on Dec 20, 2009

  • 141 Answers

SOURCE: how many amps does a Reakistic CB radio TRC-474

4 amps MAX

Posted on Jan 30, 2010

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1 Answer

Good day I have an cobra 148 Gtl tx and rx a working but no out put


It might not seem obvious but on many, if not all, current CB radios have separate wires coming from the microphone for RX and TX. It seems like the mic wire for TRANSMIT may be open. It is a common failure.

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Tx red light is use to show what


when you are not talking the light should be an aqua / green color.When you transmit it should turn red. if you see two red lights your antenna is out of match.As for your radio not get out you have to get a friend to listen on another radio and he will tell you if its working or not.

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TRC-481 No sound


test the internal speaker to see that sound is indeed getting to it.Hook an external speaker to it and see if that works.you just may have to change the speaker but it could be more than that. Do thisfor now then repost as to what you did and whether it worked or not because there is more problems and they are internal. Just go with this for now and if it doesn't work you may have to get it to a tech to repair it.

Jan 10, 2013 | Radio Shack Trc-481 Cb Radio

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Have trc 457 need to clip mod limiter, what to look for?


why do you want to clip the limiter ? you will be overmodulaing the audio and bleeding over all the channels and this is great but also a good way to loose friends because while you are talking they cannot listen because your voice will be coming through their radio. the best thing to do is leave it alone and find the variable to turn the mod up then you should be at around 90% modulation .

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Need to replace microphone on a Radio Shack TRC 447 CB. 6 pin Anybody know?


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1 Answer

Key mike no hears me but shows meter


You didn't mention if you hear the other radio. If not, here's a common problem and solution.
That's usually a defective amc stage that produces RX audio and TX modulation. It's an integrated circuit that will require a tech fixing it. You will have a transmitted carrier with no modulation, and no sound in your speaker. However, make sure you have a good mike plugged in first, and substitute a known good mike to verify it's not the mike.
However, if you hear them, and they see your signal, but no talk (modulation), then the problem is usually your mike. Try another one in this case. Thanks, Bill

Jul 27, 2010 | Cobra 19 Ultra II CB Radio

1 Answer

I removed my Roger Beep from my Eagle Sidewinder 400, It still receives but will not transmit. What do I have to connect back up for it to start transmitting again? I'd be Thanking you for any help.....


If the radio is not going into TX, then you have not connected the TX line back up,

If there is no audio when you TX you have left the audio wire off.

The radio usually needs 4 wires.
TX (Puts radio into TX)
Audio (this carries the audio from the mic into the modulator)
Screen (ground cable (earth))
RX (not as common these days)

May 18, 2010 | Radio Communications

1 Answer

No receive cobra 29 ltd classic


Hi and welcome to FixYa,

Initially, pls confirm that there is modulation (transmit audio). The reason I asked is if IC4 (TA7222P) is blown, then the radio would have no audio amplifier which would explain no receive audio. Additionally, the final and pre-final (TR15 & 15) gets is modulated TX+12 through D8 from T1 which in turn is the output of IC4 through C48.

Perhaps a schematic diagram may be of further help.

Good luck and Thank you for using FixYa. Happy Holidays.

Dec 18, 2008 | Cobra 29 LTD CB Radio

1 Answer

When I Press the mic to talk, others hear me key down, but no sound is transmitted


Hello lummox30,

Check you mic first to see if it is indeed working. Then if it is the below advice is applicable.
It sounds as if your TX audio amplifiers might be malfunctioning or the TCXO might be bad. If you have a background in Electronics I would suggest that you open up the unit and using a dummy load on the antenna check the two TX audio amps to see if when you key the mic and speak into it the amplifiers are amplifying your voice and sending it to the modulator. If the problem is not amps or the filters in between the amps, the modulator and the VCO buffer are suspect. If the TCXO is being modulated I would check the PPL IC and the Drive amp to see if the modulated signal is getting through. The last two checks I would perform are on the final amp and the TX switch prior to the antenna jack.

If you do not have a background in electronics, still check your mic, but the rest of the above advice can be done by a qualified Radio Technician.

I hope this helps,

Thank you,

Shuttle83

Oct 01, 2008 | Maxon MCB-30 40-Channels Base CB Radio

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