(Topic ID: 310178)

DE Guns N Roses Sound Board Noise/Distortion

By Md2020

6 months ago



Topic Stats

  • 5 posts
  • 1 Pinsider participating
  • Latest reply 5 months ago by Md2020
  • Topic is favorited by 1 Pinsider

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#1 6 months ago

So, I thought I had it all figured out.
The sound board makes a lot of distorted/garbled noise.
The PO told me it was a voltage regulator. I replaced both VR1 and VR2 on the soundboard.
I also found VR1 on the power supply damaged, so I replaced that as well.
I tested the voltages coming to the soundboard and they seemed OK compared to what I've read around the forums: +12= +11.2vdc +5= +5.1vdc -12= -14 vdc.
The AC ripple I'm getting on the +12v side is around 300mv or so. Not ideal, but I didn't think that would be causing this.
I've been mulling it over and I'm wondering if it's possible all 3 output amps could be blown.
Here's a video of the audio in diagnostics

.
You can hear the "sounds" underneath all the s*** somewhat.
Any ideas? I'm about to pull the board out again and hit with my ESR to see what I can see

#2 6 months ago

I just made a junk headphone "scope" to trace back where the audio is getting fuxated. I probed into the output of the TDA8199 amplifier (U35). Pure shite distortion. My initial theory was bad output amplifiers. But, in this case, it's "garbage in, garbage out".
Wanted to check capacitors first, but I had an LCR meter- not an ESR meter. Worthless.
Can a guru point me in some sort of direction?
I'm pretty limited as far as specialty tools. It's been crossing my mind that it may be time to buy an O-scope. I'd have to be taught how to apply it, though.
tl;dr- bump

#3 6 months ago
Quoted from Md2020:

I just made a junk headphone "scope" to trace back where the audio is getting fuxated. I probed into the output of the TDA8199 amplifier (U35). Pure shite distortion. My initial theory was bad output amplifiers. But, in this case; "garbage in, garbage out".
Wanted to check capacitors first, but I had an LCR meter- not an ESR meter. Worthless.
Can a guru point me in some sort of direction?
I'm pretty limited as far as specialty tools. It's been crossing my mind that it may be time to buy an O-scope. I'd have to be taught how to apply it, though.
tl;dr- bump

#4 6 months ago

Just a little bumpy-poo

#5 5 months ago

No leads? I'm trying to avoid a shotgun approach

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