Moog 901a / 901b DIY

noddyspuncture · Joined: Dec 12, 2011 Posts: 2 Location: UK

Thanks Tim, already did that. It was he who suggested I post here...!
I think I have found a work around... looking at the actual Modular pcb layout I think I can suss it.

Cheerz anyway.
Tom

3nity · Joined: Oct 10, 2008 Posts: 13 Location: west

ericcoleridge · Joined: Jan 16, 2007 Posts: 889 Location: NYC

I remember seeing a Moog Modular Service Manual that included schematics and PCBs with parts overlays. I tried to find it again recently and I couldn't. But I'm sure it must be somewhere on the web still. If you just search for every moog 900 service manual scan and look through them I think you'd find it.

living sounds · Joined: Mar 27, 2009 Posts: 9 Location: Germany

Wow, the example is pretty much the best sound I've ever heard in terms of synth bass!

Could someone please point me to the schematics/component layout for the discrete mixer?

And yes, the component placement for the VCOs would be great.

dingebre

dingebre

dingebre · Posted: Mon Apr 15, 2013 10:58 am Post subject:

I just got a note from the Sears order department, my order of the 871999127 - Diode CL-1 has SHIPPED!

Wow. I wonder if they have any other bizarre parts...

I'll post some photos when they arrive.

David

dingebre · Posted: Fri Apr 19, 2013 6:30 pm Post subject:

Peake · Posted: Sun Sep 15, 2013 3:16 am Post subject:

Little kick for interest and experimenters. Note: Still unconfirmed. Use the Moog Modular Service Manual for reference and to answer any parts values/layout questions. This version is slightly different than the version in the Service Manual.

Peppy · Joined: Feb 10, 2021 Posts: 30 Location: heide

Peppy · Joined: Feb 10, 2021 Posts: 30 Location: heide

I still have a stripboard design that I created, not nicely done by me, but it serves its purpose, it's a PWM mod, you can find the original schematic on: Analog-Monster.de

Many thanks to Carsten (Analog-Monster.de) for his valuable work adding a PWM to the Square!

pwm analog monster stripboard 2.png

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blue hell · Posted: Sun Dec 18, 2022 11:42 am Post subject: Re: 901B more Information !

Peppy · Joined: Feb 10, 2021 Posts: 30 Location: heide

What I would like to mention is an experience! Many have problems scaling the VCO to more than 2 or 3 octaves, me too! I've tried many things and often managed to give the vco good tracking on 3 octaves, over 4 octaves was hardly / not at all possible for me!
I reduced my R18 (3.3M) to 491K resistance, then it worked VERY WELL to scale the VCO to 5 octaves. VERY IMPORTANT: Let the VCO warm up for 60 minutes and no less and then start to get the octave tracking right!

Due to the reduction of R18 (901A) from 3.3M to 491K, I have not experienced any other negative effects!

PWM note: Here R29 should be changed from 13K to for example 24K, I kept this resistor with 13K and the PWM still works well!
PWM is an incredible gain for the VCO !