Very Low Volume on a COBRA 2000GTL

[714sandman]

I just got back into CB after 40 years. One of my Cobra 2000's has a problem with very low volume that doesn't respond to changing the volume pot. Also, squelch is non responsive. I noticed this when I first got it and truth be told it was a $20 garage sale score so I wasn't mad about it. I let it rest and well I have some time today...
So today I fired it up and low and behold, there's the volume you'd expect! Squelch worked, everything seemed right with the world.... So I opened it up, cleaned all the controls because I figured it must be that. Alas, it happened again. I used deoxit and blew them out with air a few times, but the volume is barely audible again and squelch non responsive.
I just confirmed transmit and receive. The other party was transmitting and I can see the needle deflection of their signal, but I couldn't hear them whatsoever, even faintly.
I found the 2000gtl schematic and well honestly, if it ain't point to point and about 50 components total, I get lost - really lost. This is a huge schematic for me to read and I can't even FIND the volume pot on the schematic!!! ALSO, IS THERE A TRACE MAP SOMEWHERE???
I have an iron and all the electrolytics anyone could need, but I DON'T have any idea where to begin.
Your advice would be greatly appreciated.
714Sandman

[Jetman]

Sandman, replacing the caps is a good bet. Also if you power on the radio and take you thumb and press a little in the center of the main board with enough pressure to flex the pcb, see if it causes the issue to come and go. That would inicate a cold solder joint. Sounds more like the audio amplifier (IC6) is going out. They are still available on eBay. Just look for TA77222P. Hope this helps

[714sandman]

Sandman, replacing the caps is a good bet....Just look for TA77222P. Hope this helps

I can't find that - TA77222P - the number must be off Jetman...?

So get this, I come in this morning, turn the radio on and the audio and squelch function is back!!!
Ok, so I figure I have an intermittent problem OR the heavy Deoxit bath I gave it yesterday cleaning the pots needed to dry out - even though I blew it all out with an air compressor. I have had that happen before.

Yesterday I was inside this radio for the first time and I see now that it has been modified with extra channels and who knows what else. I am slightly better than a "YouTube Tech" so I am unsure what else may have been done. Looks like the radio was modified to work on 10 meters as well. Apparently the clarifier is unlocked too. I am unhappy about this but as I said, it was a very cheap garage sale find.

I bought all the electrolytics for the radio but MAN I didn't want to remove the board to do the job. I was hoping there were trace/component layout drawings somewhere but I haven't found any yet. Do they exist?

[MDYoungblood]

It should be a TA7222P (not TA77222P) (IC-6 on the schematic and board ID), you will find it on the right side of the board toward the back. The DeoxIT probably helped but plugging it in and letting it warm back up after sitting a long period of time helps too. I would recommend a recapping to wake it back up completely.

3's

Greg

[714sandman]

Ok I found that MDYoungblood, thanks. Its been on for awhile now. The Mrs. is at home with the other 2000GTL, I am waiting for her so I can confirm receive. It has intermittent static now too. Yeah, this bad boy needs a lot of work.

[jessejamesdallas]

Sandman, replacing the caps is a good bet....Just look for TA77222P. Hope this helps

I can't find that - TA77222P - the number must be off Jetman...?

So get this, I come in this morning, turn the radio on and the audio and squelch function is back!!!
Ok, so I figure I have an intermittent problem OR the heavy Deoxit bath I gave it yesterday cleaning the pots needed to dry out - even though I blew it all out with an air compressor. I have had that happen before.

Yesterday I was inside this radio for the first time and I see now that it has been modified with extra channels and who knows what else. I am slightly better than a "YouTube Tech" so I am unsure what else may have been done. Looks like the radio was modified to work on 10 meters as well. Apparently the clarifier is unlocked too. I am unhappy about this but as I said, it was a very cheap garage sale find.

I bought all the electrolytics for the radio but MAN I didn't want to remove the board to do the job. I was hoping there were trace/component layout drawings somewhere but I haven't found any yet. Do they exist?

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