Hey JPK, running in to a good bit of noise on the output of my MU524 and I'm not quite sure what's causing it. It's a hissing/static type of noise. The noise ONLY increases when I turn up the output. The input knob has no impact on the level of noise coming out of the unit. I'm assuming this means it has something to do with the output stage.
Troubleshooting I've done so far:
- Checked an reflowed any solder joints. I couldn't really find any but I reflowed a couple of them that were not as good as others.
- no reversed components
- no component leads touching the back plate
- Nothing seems to be touching the transformer
I read through @egelmett's thread about noise issues as well and tried to see if there was an overlap.
I do have some similarities with his issue and the way he describe the noise being effected by the cover plate. However, even with the cover plate off mine is still giving off a good bit of hiss. just a little bit less.
I tried tapping pieces with a pen and screwdriver and there's only been one thing that has made any difference so far. The Voltage Regulator. The spacers/screws near the voltage regulator were also the ones that made the most difference with noise.
If I tap a screwdriver to the coil on the voltage regulator the hissing completely stops. The unit also still passes audio through when I do this at the same level. I have only been doing this for a couple of seconds at a time as I'm not sure if that could potentially damage anything by doing that.
Does this point to the voltage regulator being an issue or is it something else and this behavior with the voltage regulator is to be expected? Also, just simply moving a screwdriver around the coil without actually touching anything shifts the noise as well.
Thanks in advance!
