Another PC122XL TX Problem

[sonoma]

sounds like another good radio is about to be brought back to life.
Low_Boy you just made a bad radio good again.
after Andy got into this radio I knew you would find the problem. these little radios are one of the best I have used . like I mentioned earlier in your post I have 2 PC122 radios, 2 trc453's, 1 trc-465, and 1 PC122XL's. . I will not sell any of them. can only use one at a time but like having them.

 

[Low_Boy]

Sonoma you're absolutely right. I have another sitting here hooked it up last Sunday talked Skip all over the place Barefoot. It,s a great radio

 

[kaos513]

I did bring mine back from the dead works great.

 

[Dmans]

I see something may have struck the jack -

Maybe in it's prior ownership someone told the operator to "Hit his Kicker"!

Good catch Low_Boy. Sometimes the eyes are the best diagnostic tool!

73's
David

 

[Low_Boy]

That was the last spot I would have thought the problem would be. They surd did use the kicker LOL.

 

[Low_Boy]

I have my work cut out for me.

 

[kaos513]

Save that peace apoxy it back then work around it

 

[Low_Boy]

Already back in.

 

[kaos513]

Great!

 

[kaos513]

Makes sense hope nothing else went bad keep fingers crossed.

 

[Low_Boy]

It,s Working but not out of the woods yet. Something is shunting the modulation only in cb mode. In pa full modulation, In AM or SSB you get a word then modulation falls back like the limiter just kicked in. but instead of bouncing back you loose modulation until you unkey and key then you get a word and the same thing happens. If I get a chance tonight I will remove the limiter and try it. Possibly a cap. not holding charge.

 

[kaos513]

one step closer

 

[Low_Boy]

Is the modulation limiter for this radio TR27? If so and that checked good what else would be killing modulation after the first word? TR36 and TR37 are amps and check good.

 

[kaos513]

You may wanna check the audio amp chip

 

[Handy Andy]

Sounds like an open trace. Hows' the AM regulator doing?

In the audio path - even the PA amp can get in the way.

One word, then cutoff, sounds like the Mic amp is turning on, but then shutting off, due to a TX switch issue, or a line is open - can't drain off a charge.

- check AMC and ALC control trim pots in the rear. TR34 for ALC and TR28 takes in that as well a AMC from the AM Regulator section and amplifies it to make the limiter work. Limiter is Tr27 - I'd pull that and if operation is normal - the ALC and AMC circuits need to be figured out and fixed...

ALC is SSB if left on due to bad parts, can "clip" the audio and force TR27 to clamp due to the control senses carrier too. Its' turned off by a diode (D41) from the AM mode side of that switch. IT equalizes or powers both sides of the ALC sense - rendering it unable to amplify anything.

Look at the TX section, and mid-section by network coils for shorts or broken traces.

You had a busted mic socket - there may be more twists and turns in this radio.