I just recently got my micromoog repaired and cleaned after having a broken trim pot. I paid a lot of money to get this done and I seem to have a problem with it already. When I make basic, un-modulated sound on it with no attack, there seems to be a pop sound right when i press the key. Does anyone know what could be making this happen? Faulty repair maybe? Could it be the trim pot that they replaced? any help would be greatly appreciated.
if the attack is set to open the VCA real fast, the signal level is rising from zero to max in less then a oscillators cycle. This sounds like a pop. It should be very less obvious, if the oscillators are set to higher frequencies by means of the range switch and/or the keyboard.
If it still sounds like before, then I would gues it is caused by a wrong adjusted VCA.
Till is likely correct.
Sounds like a VCA DC offset adjustment.
To (hopefully) cure it, let the synth warm up a few minutes, turn off the oscillator and suboctave, open the filter fully, emphasis at 0, set the attack and release to 0, turn your amp up and adjust the VCA trimmer until the thump is at a minimum.
The correct setting will be approximately in the middle of the trimmer’s travel.
Too far right or left will increase the thump. Find the quietest spot in the travel of this trimmer, set and leave alone. Then enjoy… 
When I did this, i actually ended up turning it all the way to the left before the pop seemed to decreased, is this still not right? the pop still hasnt gone away completely either.
Unfortunately, it sounds as if it will require additional repairs.
If it didn’t do this before you took it in for repairs (I don’t know if the original repair had anything to do with this), you should approach the last tech and explain the new problems. If he’s reasonable, he will take it back and make it right.
VCA circuits are not terribly complex, but should be performed by someone qualified. If he refuses, find another service center or sell it as-is, with the problem honestly declared. My advice anyways. Sorry you’re experiencing such problems. 