Cobra 29 LTD ST no/low receive

DDBL22 · Post by **DDBL22** » Friday 7th Jul 2006, 12:53

My 29 LTD ST transmits clearly but I can't figure out why I can only hear others if I get really close to the speaker. And then I can only hear a soft crackle of a voice. I know some other models have a capacitor problem, but I'm not sure about this model. Any help would be appreciated. Thanks... DLO

Rick · Post by **Rick** » Saturday 8th Jul 2006, 12:06

Check IC4 (TA7222AP). Switch the radio on and leave it no for a minute then touch the IC if it is very hot, then replace it as it has gone short.

Rick.

DDBL22 · Post by **DDBL22** » Sunday 9th Jul 2006, 5:32

I plugged it up for a while.....I couldn't feel any heat coming from IC4. Would it be really hot? I might not be able to feel it if it's dissipating heat through the CB housing. Thanks, DLO

Rick · Post by **Rick** » Sunday 9th Jul 2006, 10:11

The next to try is the PA. Plug extension speaker in to the PA socket switch the radio to the PA mode key the mic and speak there should be some output from the extension speaker, if there is no output the Audio IC4 is duff (and not the beer) just replace it, but if all is ok check with a DVM at the collector of TR12 and open and close the squelch the voltage should be about 9.2v to 0.5v if ok then try C34 33u at 16 volt I have had this cap go short.

Rick.

DDBL22 · Post by **DDBL22** » Monday 10th Jul 2006, 7:27

I've plugged a PA in before and we could hear it loud and clear. I just checked TR12...the max I can get from it is 0.64 volts. What's the next step?? Again..thanks for your help!!!

Rick · Post by **Rick** » Monday 10th Jul 2006, 9:34

Remove TR13 or left the collector, and tell if you get the audio back.

DDBL22 · Post by **DDBL22** » Tuesday 11th Jul 2006, 15:33

Well I just removed TR13...It didn't change anything. I can still barely hear the tranmissions if I put my ear next to the speaker.

I put TR13 back in....

What's next? Could it still be that Capacitor?

Thanks, DLO

Rick · Post by **Rick** » Tuesday 11th Jul 2006, 22:14

If you have removed TR13 and it didn't change anything and you told me that the voltage at TR12 max was 0.64 volts the fault has to be TR12 or TR13. If you have a small head phone the ones you get with a walkman, but it from the center connect of the volume control and ground you should have good audio .

DDBL22 · Post by **DDBL22** » Friday 14th Jul 2006, 10:12

I'm not sure which leads are coming from the volume pot....are they the white and black leads?

Rick · Post by **Rick** » Saturday 15th Jul 2006, 3:44

I think it would be best if you take it to some one who can sort it out. Sorry I can not help any more.

Rick

DDBL22 · Post by **DDBL22** » Saturday 15th Jul 2006, 9:36

thanks anyways

DDBL22 · Post by **DDBL22** » Monday 17th Jul 2006, 10:17

Anybody else got a clue? I really like this radio, so I'd like to get it working again.

Pioneer621 · Post by **Pioneer621** » Wednesday 26th Jul 2006, 9:54

Hi, Have you tried plugging a good external speaker in the EXT Speaker jack in the back of the radio. I have had a blown speaker in the radio put out slight sound before but you really had to turn it up to make out what was being said, so if you have not tried that its always worth a shot.

Also, Does your meter show high S-readings when you receive a strong signal? If you can hear your voice through PA loud and clear and when you transmit as well, that pretty much rules out the AUDIO chip of being bad. Sounds like maybe something in the receive circuit, maybe the I.F gain VR is set to low or maybe you need a complete receive alignment.

I hope you get it figured out, the 29 LTD radios are GREAT. I have had quite a few of those radios that I fixed / restored & tuned up. I have not had that problem with the ones I repaired, so I am not really sure what it could be. You may want to check the MIC cord for a bad RX wire as some radios I have had still put out a very slight amount of sound even when the MIC is unpluged so you may want to try a known working MIC. cbtricks.com has the schematics for the 29 LTD as well as the service manual, so you may want to check that out and see if you can determine the problem from that info. Again I hope you get it figured out!!! Kyle.

DDBL22 · Post by **DDBL22** » Thursday 27th Jul 2006, 9:58

Hey thanks for posting!!

Well this is what I do know:

If I plug a PA into the back and speak into the mic, its loud and clear. When I transmit to my buddy's CB, he can hear me loud and clear. Nothing looks burnt-up inside.

I will look into the other things. Again thanks for posting!!

DLO