Moog Music Forum

Update: R514 was acting up and VCF Balance was improperly set. Fixed R514 trimmer and adjusted the voltage to where it should be and there you go, Filter Tone is back. Thought I'd share the resolution to this problem.

Sent you an e-mail.

Thanks for your help with this! Can you clarify what you mean by setting up the board for normal use?

Also to clarify, the Tone is completely inaudible after 3-4secs of the synth booting up. So it's not like I can initiate it again once it disappears, it's just gone from the audio signal. To ...

I have it set up as they are suggesting in the Service Manual.


I. VCF not passing signal. Reason undetermined.

Set controls according to Figure 5-1

1. Insure the input signal of roughly 40 mV p-p appears at base of Q501. (PIN 4)

2. This same waveform should appear (40 mV p-p differentially ...

I'm getting the following for IC502.

1 - 2.48V
2 - 1.52V
3 - 0.85V
4 - 1.52V
5 - 2.48V
6 - 7.60V
7 - 6.94V

8 - 15.00V
9 - 7.60V
10 - 6.94V
11 - 15.00V
12 - 0V
13 - 0V
14 - 0V

Are you referring to taking measurements from IC502?

I just mean that when I first tune on the unit, and let's say it's set to Bypass for an 'always on' Tone, I will hear it peak at the initial boot up, but then it slowly decays and become inaudible with some intermittent audio crackles. Envelope is at full sustain in this case so it should just be a ...

IC601, IC602, IC302, IC501 and Q512, Q513 have all been replaced without any effect.

I wonder if switching out C507, C513 and C707 might do the trick. Old electrolytic caps from the late 70s starting to act up?

There's gotta be someone out here who knows a bit more about schematics to help me out here. :)

I'm trying to diagnose an issue with a Micromoog I just acquired. The issue is that as soon as I turn on the synth, and have it set to Tone, I can hear the tone but then it slowly drifts and goes quiet ...

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

Definitely does have that Colonial Maple 223 vibe. But unless I saw it in person (versus on screen) I couldn't say for sure. It has that bit of orange in it. How bad is the scratch?

Edit: Gunstock 231 might be it too... They're kind of close.

I had the 8-voice originally, then switched to the 16-voice. I don't hear any difference in the fan noise honestly. They operate very quietly on both. If your space is not overly hot, the fans usually stay at the lower speeds.

And trust me, if you get the 16-voice, you'll be glad you didn't get the ...

I would suggest that functionality to Moog. It might be possible to implement. They could add a feature in the sequencer (send to arp) or something like that. The sequencer would then be dictating what the arp is playing off of. Nice idea!

They didn't fix a kind of small thing that I've been asking for since Moog One came out. I will send it to them again since I think it's actually a fundamental issue. Basically, when you use any LFO to modulate the WAVE angle and that LFO is unipolar, the Modulation direction is inverted, which ...

Reporting back with the little bit of time I just spent with 1.5.

I have to say that most of the issues I had with it are now GONE! The little clicks and pops from changing settings / preset / parameters are absolutely gone. It doesn't seem like much but not having these little digital noises was ...