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no audio

Sam Tedesco
 

Hi everyone. It's that time again.... Opened sunil case w/ v4 board to add audio amp. Removed audio pin 7 to the front input board and brought audio to amp from d16. Hooked internal speaker to amp and it worked great. Added front audio input and got buzzing/oscillations over audio. Turned off, removed front input, turned on, no audio. Took everything off amp and put audio back to board...nothing. changed q71, 72, and 73...nothing. Any ideas?? Thanks 

 

Not too clear what you did as I have not used Sunils case.

Sometimes the culprit in such case is the EP socket. Some plugs have a different tip shape and may damage the contact
inside the socket. If you used an external speaker through EP socket then check that.

Raj

At 07-06-19, you wrote:
Hi everyone. It's that time again.... Opened sunil case w/ v4 board to add audio amp. Removed audio pin 7 to the front input board and brought audio to amp from d16. Hooked internal speaker to amp and it worked great. Added front audio input and got buzzing/oscillations over audio. Turned off, removed front input, turned on, no audio. Took everything off amp and put audio back to board...nothing. changed q71, 72, and 73...nothing. Any ideas?? Thanks

 

What type of amp are you using. I remember using a type-d with my sota beams filter and needed to keep the GND isolated from radio/earth gnd.

Maybe try the audio jack when its not attached to the case and see if it works if so you know.
--
David

 N8DAH
Kit-Projects.com

Shop is open!

Sam Tedesco
 

David and Raj, thanks. I already tried both of your suggestions. I'm using Sunil's audio amp. I removed the amp and reverted to just the standard ubitx setup, and I have no audio... even at the pre-amp stage. I'm stumped...

Mark Hatch
 

I assume those front panel jacks are not grounding to the case?  The early (smaller) Sunil cases attached the bottom handle right under that front board and it would ground out. I had to get my dremel out and then some electrical tapes to isolate these points from the front board.

BTW: I "think" i blew the standard audio push/pull transistor set q72/q73 when trying to install the amp. I replaced them both and never tried installing the amp again. So no certainly not confirmed that I didn't do something else wrong.

73
Mark

Joe Puma
 

I dremeled and grounded all metal contacts to the front case. 



On Jun 7, 2019, at 11:18 AM, Mark Hatch <mark2382@...> wrote:

I assume those front panel jacks are not grounding to the case?  The early (smaller) Sunil cases attached the bottom handle right under that front board and it would ground out. I had to get my dremel out and then some electrical tapes to isolate these points from the front board.

BTW: I "think" i blew the standard audio push/pull transistor set q72/q73 when trying to install the amp. I replaced them both and never tried installing the amp again. So no certainly not confirmed that I didn't do something else wrong.

73
Mark

Sam Tedesco
 

I tried isolating the amp only. Nothing. I tried a radio shack amplified speaker on just the audio section of the main board...pre and post amp. Nothing. I tried isolating only the front panel. Nothing. Receive is gone. ???

Arv Evans
 

Sam

Difficult to troubleshoot remotely without more information, but if there is no local
oscillator signal into the BFO mixer there would be no audio output from that stage. 
You might connect your external audio amplifier to the output of the BFO mixer to
see if there is audio there.  The level will be low, but audio should be heard on
strong signals. 

Arv
_._


On Fri, Jun 7, 2019 at 1:38 PM Sam Tedesco <stedesco619@...> wrote:
I tried isolating the amp only. Nothing. I tried a radio shack amplified speaker on just the audio section of the main board...pre and post amp. Nothing. I tried isolating only the front panel. Nothing. Receive is gone. ???

Evan Hand
 

Sam,
can you fill us in on what test equipment you have?  I would start by measuring voltages on the RX tags listed in th3 schematic.  I would then try supplying a signal to the audio section (sometime the hum from touching th3 test point is enough). 

If I am reading your comments correctly, I think you may have a short somewhere in the RX power supply.  ESP if all of the audio sections are down. That was wh6 testing the voltages first, the going to audio signal injection to see where the signal is lost. 

Good luck, and happy hunting:)
73
Evan
AC9TU

Sam Tedesco
 

Tried injecting audio. No go. I might have to venture before the mixer. I'm lost on this one

Arv Evans
 

Sam

Confused here.  You said you do not have an oscope, so what is it that is making weird lines?

If injecting audio at the mixer output did not produce audio at the regular output then you have
probably isolated the problem to between the mixer and the audio output.  Follow the audio
path on the schematic and inject audio (use a 0.1 mfd cap for DC isolation) at each stage
in the signal path from mixer output to audio output.  At the point where you start hearing audio
measure DC voltages and look for any that are different from normal values.  If voltages near the
fault are all normal then you will probably need to look for an open in the circuit path (cold solder
joint or possibly a bad component). 

Arv


On Fri, Jun 7, 2019 at 8:31 PM Sam Tedesco <stedesco619@...> wrote:
I have most test equipment. Except for an oscope. All it ever does is make weird lines! 

Lawrence Galea
 

You do not start from the mixer.
You start from the audio output stage
Try injecting audio backwards from the audio output stage.
If you get audio out the output stage is OK
Then move backwards to the mixer testing each stage at a time and as long as you have output the stages following your test point will be working.
When you have no audio from a test point the fault will be between that point and the previous test point.
Regards
Lawrence

On Sat, Jun 8, 2019 at 4:29 AM Sam Tedesco <stedesco619@...> wrote:
Tried injecting audio. No go. I might have to venture before the mixer. I'm lost on this one

Sam Tedesco
 

I started at the output and have been working backwards. Changed a few transistors on the amp stage. Just checked preamp. No audio to be found. On to the mixer. My dad has a nice audio injector that I need to try. My setup is a little cumbersome. So far, voltages seem fine to amp

Sam Tedesco
 

Got it. Thanks for all the suggestions