Hello,

I just received a Mediavision Thunderboard and probably need some assistance determining where its defect comes from.

It sounds like massive clipping or as if not all bits come through, but only the upper ones, but I think it is more like a gating effect, since it depends on the selected volume level. The issue happens independend if digital audio or OPL2 audio is being played, so it must be located in, or more likely, after the DAC. The higher you crank the volume via the knob, the more sound passes through.
It appears that only the louder parts of a sample come through, again, depending on selected volume levels by the volume knob. Only louder parts pass through and appear distorted, as if some electronic part would only switch if there's a certain voltage reached, instead of working on a (mostly) linear level.

I'm not too much into electronics (yet), so I assume these things:
- Bad capacitors (The only electolytic one measured perfectly fine, didn't test the tantalum ones yet)
- Bad amplifier (386N-1 is used, behind volume knob)
- Possibly bad volume potentiometer (but it doesn't crackle)
- Bad voltage regulator (LM340T5 in use, top right on board)
- Bad DAC (possible, but wouldn't explain why changing the volume changes the effect of pass through)

Here's a picture of the same board: http://www.amoretro.de/2014/09/media-vision-t … underboard.html

Here's an example recording: It starts with an Adlib track with first lower volume, then an increase via the volume knob, then another increase.
https://badsector.de/download/sound_issue.mp3

Is there someone who could point me into possible directions? Thanks in advance!