Pc76 audio chip

[Dirty Duck]

 

[Dirty Duck]

 

[Cable Guy]

That transistor that I circled is Q18, it's your limiter. It is covered in a glue that needs to be removed. The glues they used turn corrosive and conductive with age. If that glue has gone conductive, it can pull your signal to ground there. That is the purpose of that transistor, to pull the mic audio down when it gets too high, limiting it. Conductive glue is fault of many radios in the dump, but patience can fix it. If it's hardened, chip away at it carefully. If soft, pull it off carefully. If it's went corrosive, you may have to replace components. Just clean it off and see if your mic audio comes back.

 

[Dirty Duck]

View attachment 73932
That transistor that I circled is Q18, it's your limiter. It is covered in a glue that needs to be removed. The glues they used turn corrosive and conductive with age. If that glue has gone conductive, it can pull your signal to ground there. That is the purpose of that transistor, to pull the mic audio down when it gets too high, limiting it. Conductive glue is fault of many radios in the dump, but patience can fix it. If it's hardened, chip away at it carefully. If soft, pull it off carefully. If it's went corrosive, you may have to replace components. Just clean it off and see if your mic audio comes back.

I’ll get to it asap tonight. I’m doing chores right now. I never would have figured glue but, it makes sense.

 

[Dirty Duck]

View attachment 73932
That transistor that I circled is Q18, it's your limiter. It is covered in a glue that needs to be removed. The glues they used turn corrosive and conductive with age. If that glue has gone conductive, it can pull your signal to ground there. That is the purpose of that transistor, to pull the mic audio down when it gets too high, limiting it. Conductive glue is fault of many radios in the dump, but patience can fix it. If it's hardened, chip away at it carefully. If soft, pull it off carefully. If it's went corrosive, you may have to replace components. Just clean it off and see if your mic audio comes back.

I’ll get to it asap tonight. I’m doing chores right now. I never would have figured glue but, it makes sense

 

[Dirty Duck]

alright I Removed the glue “concrete lol” and I officially have transmit and receive again.

I’m not surprised but the receive is poor and I’m not sure on how well it transmits.

But it does both now so that’s a plus!

I had to take my antenna down for maintenance. I’m currently testing the radio in my vehicle.

 

[AudioShockwav]

The glue, actually Sonybond, has resulted in as many dead radios as dried out caps, even worse when it starts eating the leads off of components.
Nasty stuff, if you see anymore get rid of it.

73
Jeff

 

[Cable Guy]

alright I Removed the glue “concrete lol” and I officially have transmit and receive again.

I’m not surprised but the receive is poor and I’m not sure on how well it transmits.

But it does both now so that’s a plus!

I had to take my antenna down for maintenance. I’m currently testing the radio in my vehicle.

Congratulations, you fixed your radio. Now a good alignment is in order. Also, look for any more glue like that and try to remove it. I have a 76xl here without the weather band and it also has glue on the limiter, but it's only lightly touching the tops of the components. Yours looks like it seeped down around the pins, where it can do the most damage. Good luck.