Alesis Micron.. I can't figure this out

@kvitekp thanks man! This information is very helpful. I will test and report back.

@schrab no signal at U7 pins 3,12. I shorted pins 1,2 and 5,6 of the volume pot pcb connector. Output signal was not restored. I checked C44-C47 and did get a signal on all of these.

@kvitekp I checked all of the pins on U5 and didn’t get any signal.

Is there a signal at negative pins of C45,46 after shortening pot connector?

@schrab I will check that.

Ok, you have signal at point A and no signal at B, so check everything in between, also check B to ground resistance, it should not be shorted. You can also apply some line level audio signal to point B (to avoid desoldering of U7) and listen to main/headphone outs.

@schrab if I had signal at C46, could I rule out anything being a problem before that?

Put the pot connector back. Check again. If signal lost - the problem is pot/pot pcb/cable.

@schrab what are your thoughts on U5 shunting the signal?

not sure, but they are looks decoupled with C42,C55. And first you have to get signal at B points. Did you try to apply external signal to B point?
In such cases i’m usually replacing all suspicious components i have spares for =)

@schrab I haven’t tried to apply external signal to B point. How would you recommend I do this? Hookup my iPhone (music) cable to the mono cable that connects to the audio probe? Basically the reverse of using an audio probe? I’m sorry for my ignorance. Also, I haven’t done any SMD soldering since I soldered the Midipal, let alone remove the TL084 from the mainboard. I was planning to clip the leads on the TL084 and bend it back and forth until it breaks off, then apply solder and wick off any excess. It sucks that that TL084 is stuck between a few caps. I think it will be challenging to do the replacement. Though I am optimistic. :slight_smile:

You’re abolutely right about reversed audioprobe.
Clipping legs is good but irreversible. If you want to save the IC first remove surplus solder from all pads with a wick, than heat up legs and bend it up slightly (until disconnected from pad) with a toothpick one by one. Just a tip. In your case with spare 084 you can act rudely.
Removal of SMD resistors/caps is much easier - grab it with tweezers in the center than simultaneously pull up and heat both pads alternately until desoldered.

Using enamelled wire is a good way of lifting SMD legs if you want to do a lot of them.

@schrab great! I don’t care to save the IC really. I’m more concerned about damaging the pads. Do you know where I can find the B point on the mainboard?

@6581punk like a 42AWG enamelled wire? I’m guessing it needs to be pretty thin right? Slip the wire underneath several legs and pull as you apply hot solder?

@xtrmnt point B is U7 pins 3,12, also C45,46 negative pins. Look at this post attachment.

@schrab thanks!

@schrab I did get faint audio at point B 3,12, c45, and c46 when applying an external signal. I replaced TL084 and got synth audio out of the headphone jack, but not the left and right audio channels. So I decided to solder J111s into Q2 and Q3. Now I have no synth audio from the headphone jack or left and right audio channels.

@schrab I just clipped off the J111s at Q2 and Q3. The headphone jack is now working again. I decided to probe the leftmost drain of Q2 and Q3. I get a good signal out of Q3 drain but no signal from Q2.

@schrab I get signal at pin 3 of U7, but nothing on pin 1 or 2 of U7. Could U5 be shunting the left audio channel output?