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Galaxy 959 No TX audio or PA audio. I thought it would be easy

Low_Boy

Low_Boy

Sr. Member
Jan 21, 2010
1,934
1,198
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Rochester N.Y.
I have a Galaxy 959 with no transmit audio or PA audio this is on AM and SSB. Some how the roger beep is sneaking through. It has receive audio. My first thought was a easy, audio amp. the new 2003 style. No still not working. I then checked Q54 and Q55. all check good. I figured possibly the limiter Q39 that checked good. I do get a dead key in AM from 2 to 9 watts variable power . Microphone is good. Any ideas of what I am missing?
 

No echo board in this radio.
Mike.. I will check voltage on pin 3 and 4.
LC I will check IC7.
First thought looking at the symptoms was a bad audio amp. I will post my findings
Thanks Guys
 
Well, a 959 has talkback, so if you have no audio - yet you say you have receive audio...

Means the audio amp works, this would be more related to the Talkback circuit (Q42) but just don't start swapping out parts just yet, this could be something as simple as a header bouncing off the pins or the TB switch getting flakey onto the TB POT itself opening up.

So while you have the foil side of the case open, try to rub or place fingers around the audio amp - if you hear a buzz the audio is there it is not the amp . It's (the problem lies in) the pipeline from the IC to the "branches" it breaks off - part of this being the TB circuit - if one of these branches has a bad or shorted part (thinking capacitor) this can wreck your day.
 
I have been crazy busy with life problems. LOL nothing serious. So I will be back on this tomorrow Sunday. By the way talk back does not work but I forget to mention that but boy does the roger beep come through the talkback nice and loud. Also one big problem I can not find a voltage chart for this radio anyplace. If someone could post a link i would be grateful. I do get the buzzing from the audio amp when touching the solder side around the amp. I did do something I usually do not do after assessing I threw in a audio amp without checking I was a bit cocky and said a easy one audio amp but I was very wrong.
Thanks
 
this is for the RCI-2950 but i would think the voltages should be somewhat similar, allowing you to compare with what you see in your radio.
hope this helps:

upload_2021-10-30_20-43-54.png

LC
 
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My go-to tool for this sort of issue is the "Digital Manual Signal Injector".

With one hand, key the mike. With the other hand:

Take a small screwdriver and lay one finger (digit) alongside the shaft.

Touch the tip to pin 3 of IC7, the 8-pin 4558 chip.

Should manually inject a raucous 60-Hz hum into the transmit audio.

If it won't the problem is downstream from this point.

And if it does, you'll usually hear feedback squeaks along with the hum. This tells you the problem is between this point and the mike jack. The transmit audio downstream from pin 3 is working.

Would provide a starting point.

73
 
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nomadradio said:
My go-to tool for this sort of issue is the "Digital Manual Signal Injector".

With one hand, key the mike. With the other hand:

Take a small screwdriver and lay one finger (digit) alongside the shaft.

Touch the tip to pin 3 of IC7, the 8-pin 4558 chip.

Should manually inject a raucous 60-Hz hum into the transmit audio.

If it won't the problem is downstream from this point.

And if it does, you'll usually hear feedback squeaks along with the hum. This tells you the problem is between this point and the mike jack. The transmit audio downstream from pin 3 is working.

Would provide a starting point.

73
Click to expand...
Loud squeal on pin 3. Slight hum on pin 2. So the problem is between IC 7 and mic.
 
The radio is now working. I must have tested a part with a bad solder joint because after pulling and testing a few parts this is now working
Thanks all for your help .
 

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