Moog Music Forum

Im having problems with a Micromoog.

In short its low output and NO bass at all as well as the VCA creating a popping sound when set to fast attack.

But I have checked the synth thoroughly and all functions seem to work properly except for the mentioned problems.

Same Hipass result when running Pink noise into the audio input and the cutoff seems to start at around 600hz and severely cuts off at about 200hz resulting in NO low end whatsoever.
In fact when i turn down the cutoff the signal pretty much disappears.

I noticed in the service manual that the filter seems to be split into two sections.
Filter HI end ( 700hz to 1400 hz) and Filter Lo end (44hz to 176 hz ).
There could be a problem with the Filter Lo end section , it has a couple of LM 3046n Ic´s that i have tried replacing without any change.

So far i have tried changing a few caps as well as the output opamp but no luck.

Any ideas?

I have just a low resolution service manual of the Micromoog, but it seems that the filter ladder consists of one 3046 array and some single transistors Q505 to Q508. Correct me if I'm wrong. If I'm right: Did you replace the 3046 *AND* the transistors?
I recommend to replace all parts of the filter section, meaning all caps, the 3046 (if not already done) and the stand alone transistors. If the problem stays and the oscilloscope picture says the filter output is ok, you must follow the signal via the FET differential amplifier and the OTA based VCA (3080). These like to die as well.

Hope that helps...

Any luck fixing your Micromoog? I just acquired one and am having similar issues, maybe you have some ideas.