Moog parametric eq repair

Redsandblu · Jan 23, 2007

Hi,
Anyone here who works on Moog parametrics, and has replacement parts for it? The 'drive' (input gain) control's not working anymore; heard it may be a blown opamp(?).
Seems to be one of the most common issues on these eq's...Anyone's seen these issues before?
Thanks a bunch,
Raf

pucho812 · Jan 24, 2007

post pics.

Bo Hansen · Jan 24, 2007

Raf,

You can not hear the "headroom knobb" work on the Moog parametric and graphic eq, because it is a dual potentiometer that work simultaneous around both input and output amp.
When it rise the input level it also reduce the output level, and reverse.

--Bo

Redsandblu · Jan 25, 2007

Bo,
I'm well aware that it's a dual pot, and I'm not expecting to hear an apparent level change. But an increasing amount of distortion should be quite obvious...At least on the other one I worked with...It goes from a smooth distortion to an almost over the top fuzz pedal...
thanks

BrianJSiegel · Apr 1, 2022

I have the same issue. a Moog MKG seems to be working except I cannot hear any difference when using the Drive control. Maybe even a little dip in level. What would cause this? I replaced all electrolytics and the opamps seem to be okay. Maybe I need to checked each one to be sure.

mjrippe · Apr 1, 2022

MKG is the Graphic EQ, not the parametric, correct? My Moog parametric had the schematics inside the top cover, does yours?

pvision · Apr 1, 2022

I've had quite a few and none gave a pronounced effect from the Drive control. Maybe my input level was too low?

BrianJSiegel · Apr 2, 2022

mjrippe said:
MKG is the Graphic EQ, not the parametric, correct? My Moog parametric had the schematics inside the top cover, does yours?

Yes, it does have schematic which I thought was very helpful

mjrippe · Apr 2, 2022

Hmmm, I recall that a fellow engineer used to use my parametric as a distortion box. IIRC, the circuit has a treble boost on the input and a matching cut on the output as a sort of noise reduction. The result when overdriven was pretty cool.

Sorry I don't know more about the graphic. Maybe if you post the schematic we can compare the two?

Moog parametric eq repair

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