Alesis Micro Limiter Issue :(

[racer]

So I just picked up this micro limiter, I'm in love with it and have been using it on literally everything..All of a sudden it stopped working and won't play the processed signal. When I hit the bypass button, the unprocessed original audio will play and be just fine, but when I hit the button to engage the limiter, no signal. I left it plugged in for a while and maybe this caused damage, but it didn't get super hot or anything so I'm not sure. Is it worth getting serviced? Can I fix it on my own?

 

[Blue Jinn]

View attachment 106758

So I just picked up this micro limiter, I'm in love with it and have been using it on literally everything..All of a sudden it stopped working and won't play the processed signal. When I hit the bypass button, the unprocessed original audio will play and be just fine, but when I hit the button to engage the limiter, no signal. I left it plugged in for a while and maybe this caused damage, but it didn't get super hot or anything so I'm not sure. Is it worth getting serviced? Can I fix it on my own?

I picked one of those up pretty cheap, I dpn't think paying someone to fix it is probably worth it. Getting schematics from Alesis might be hard but you should ask. then pop the hood and look for something obvious at first.

What troubleshooting have you done so far? It would help us help you.

 

[jpmorris]

There's a reversed-engineerd schematic for it here:
Alesis - MicroLimiter - freestompboxes.org

EDIT EDIT: First thing, make sure the wall-wart is actually putting out 9V AC or thereabouts.


I'm not seeing the bypass circuit, but if we assume it's a true bypass like my MicroGate, the problem will be somewhere on the audio path, which is largely TL084 op-amps.
There's a couple of electrolytics in the path too, e.g. C3 and C16, but it's unlikely they'd both die simultaneously so I would assume it's one of the chips. U1 and U2 are quad op-amps which are handling both inputs and both outputs respectively so if either one of those broke down entirely you'd lose both channels.

However, everything flows through a CEM3381 dual VCA and those are pretty rare, even in the later PA381 incarnation. I'm seeing the chips go for more than I paid for the MicroGate.
Another simpler possibility is that that PSU isn't working right. It takes the 9VAC input and steps it up to +/- 12V. Make sure both power rails are delivering the goods.

If it were me, I'd check the power rails are OK first, and then take an oscilloscope. Feed a test tone into the limiter, and see where the signals goes in and out of each chip in the signal path, starting from the U1 input op-amps, then the Curtis VCA chip, then the U2 output op-amps. Look for the point where it goes in and doesn't come out again.

EDIT: For that matter, is the unit powering on at all?
Also, is anything showing on the meter when you push a signal through it? If so, that would tell us that at least U1, the input opamp is working OK.

 

[alkexjames]

I'm also having the exact same problem! I haven't used mine in a while, tried today and while its bypassed I can hear what I'm putting through and the lights are lighting up but as soon as I engage it I just get nothing, no lights or sounds!

 

[witzendoz]

I bought one of these when they cam out new, still have it but its retired really. Used it as a buss compressor on a whole lot of recordings, then I moved it to my large PA rig and put it between the desk and the crossovers as a safety limiter. The PA really cranked when you hit the micro a bit, and it also stopped guest engineers that bands brought in from blowing up the PA (as I did not tell them it was there). Mine acted up a while ago and it was actually one of the pots, I cleaned it with contact cleaner and off it went again good as new. When you hit bypass the pots are bypassed.

Alan