I realize the MK80 is a bit of a rare bird, but does anyone have any experience fixing these synths? We have one that has a soft fuzz present at all times at the outputs. It works great outside of this issue. Unfortunately that soft fuzz makes it fairly unusable.
Opening it up and looking inside, I don’t see anything obvious (like leaky caps or something). It’s in really clean shape physically.
depending on the age it, it could be at the capacitor replacement age. A constant buzz usually means lack of power supply filtering, so either the capacitors in the main power supply are timing out, or there is a failing capacitor somewhere in the audio output path.
A ground loop could also explain the buzz is there is any add on circuitry that somebody installed but that doesn’t sound like it fits this situation.
A broken grounding wire or grounding connection can also explain the buzz, if any of the audio jacks going to the audio output have a faulty ground connection it will cause a buzz. Solution just re-solder the connectors to restore the connection.
My guess is its a faulty solder joint somewhere.
if you have the ability. Unpower the unit, remove the circuit boards and do a detailed visual inspection using a magnifying tool - and look for a bad solder joints. resolder the joints to fix.
if that doesn’t work, take it to a tech.
I’m looking at a MK-80… the seller suggests that the ‘distortion’ is only appearing a couple of the patches. He was considering replacing the I/O board. Do you think it is still potentially/most likely the solder joints?
usually fuzz or distortion is a result of improper grounding, so a bad solder joint is my first guess.