Galaxy DX929 no mic audio

[Techno1]

I have a Galaxy DX929 AM radio.

There is good receive Audio and good tx and rx.

There is no mic audio and no pa audio.
If i key radio about 3 watts and turn on a radio next to i can not hear any audio when I keyup.
If i turn on the echo and then key up I can just faintly hear the mic audio with echo.
I used an audio tracer and on the in of the mic connector good audio coming from the mic. Also tried 3 different mics same problem.
Someone I think added the audio board and the pot control out front and then on the other side sandwiched between the front panel looks like a hassle to take apart and check on that area. There is the big echo board attached to the side chassis.
I dont have a good service manual to trace out the audio from the mic connector then through the echoboard in and out.

Would anyone have an Idea where to look of have a service manual for this dx929.

thanks

 

[Shadetree Mechanic]

Galaxy DX Radios Index

Galaxy DX Radios index for free technical information, user manuals and schematic diagrams

cbtricks.org

 

[SuperLid]

I have a Galaxy DX929 AM radio.

There is good receive Audio and good tx and rx.

There is no mic audio and no pa audio.
If i key radio about 3 watts and turn on a radio next to i can not hear any audio when I keyup.
If i turn on the echo and then key up I can just faintly hear the mic audio with echo.
I used an audio tracer and on the in of the mic connector good audio coming from the mic. Also tried 3 different mics same problem.
Someone I think added the audio board and the pot control out front and then on the other side sandwiched between the front panel looks like a hassle to take apart and check on that area. There is the big echo board attached to the side chassis.
I dont have a good service manual to trace out the audio from the mic connector then through the echoboard in and out.

Would anyone have an Idea where to look of have a service manual for this dx929.

thanks

You may want to have a look at the output of IC7. If it is working, look at Q53, 54 and 55.

 

[Techno1]

Superlid
Thanks I see that in the block diagram will check ic 7 out and then the 4 trannys. So this radio uses a separate chip for receive audio then a chip ic 7 for the mic audio. Older radios always used 1 chip to control both.
Thanks again will check tomorrow.

 

[Techno1]

Well I did some detective work and no good results.
I checked the mic input and good audio.
I went over to the IC7 BA4558 and no mic audio to the in on both channels and of course no output.
I checked the mic audio right in the front panel and a few components but looks like the front panel will have to come apart as the 929 also had a stock Echo board in it.
I took the echo board off the side and was able to trace some audio to the echo board and was able to get some audio with the echo board powered on.

By the block diagram the BA4558 is the mic amp and also Q53 and 55 I will check Q53 and 55 tomorrow.
So the front panel I do not have a schematic to check the echo board and how it was wired in.

Any good suggestions???

Again the radio has good receive audio.
I can hear very faintly audio with the echo board on with a radio turned on next to the 929.
Radio has about 4 watts out good receive just no mic audio.

Person who owns radio uses a stock mic and I tried his mic on another Galaxy 959 and works fine.
I tried 3 other mics and same problem no mic audio.

 

[Techno1]

Just thinking that it might not be Q53 or 55 because im not getting audio to the in of the IC7 BA4558 mic audio chip.
I would like to try to bypass the echo board but no schematic on how its wired in.

 

[Techno1]

Well i just did a bit more checking and audio is getting to the mic gain pot and back out to the Echo bd.
With audio trace good clean audio and if I put the echo on that works also.

Getting audio at all 3 red arrow locations

Not getting any audio in the the rf signal power out.

dont know what that black heat shrink part is its wired into a factory plug onto the front of radio.

Any suggestions? here is a picture

 

[Eldorado828]

Well i just did a bit more checking and audio is getting to the mic gain pot and back out to the Echo bd.
With audio trace good clean audio and if I put the echo on that works also.

Getting audio at all 3 red arrow locations

Not getting any audio in the the rf signal power out.

dont know what that black heat shrink part is its wired into a factory plug onto the front of radio.

Any suggestions? here is a pictureView attachment 68576

I have a feeling there's a control pot wrapped in that heatshrink. Probably removed to install the echo control. I think you need to pull that echo board loose to get a clear view of the installation wiring. Seems like there's something along that path if it changes with the echo board on.

 

[Techno1]

Im sure you are correct I think its the dimmer switch and the shrink tube is one with glue in side so Im going to let it stay.
I was able to get the audio work by bypassing the echo board.
On the schematic without echo board the center of the mic pot feeds resistor 202.
So I jumped that and no audio and talkback all work accept the echo.
The owner is fine with no echo. Crazy is I have no schematic to trace the mic audio in the front panel as it will have to come apart. So by jumping out the echo board IC7 is good and Q53 and 55 is good.
Gotta be something with the echo.

 

[Techno1]

So i was able to fix the radio 100% and the echo board is working also.
What i did was follow the schematic center out of the mic gain in front and feed the echo board and now radio has audio and echo with all functions. Something in the front face plate most likely a broken trace/wire. On to the next radio.

 

[doffo]

Awesome you got it fixed.