Moog Music Forum

I'd posted this over at Muff's but thought it could be of interest here as well for folks interested in replacing their old power supplies. As we now all know, early Moog modulars with 901 VCOs used +12v, -6v and -10v supplies. (The later ones with 921 VCOs ditched the -10v line). In any case, off-the-shelf PowerOne supplies are not set up to provide the 6 OR 10 volt values. However, the very helpful folks at Bel Power Solutions (who own PowerOne) provided this solution:

HB5-3/OVP-AG supply normally provides 5V @ 3A. By replacing R7 with a jumper, you can dial in -6V with the trimmer potentiometer

HBB15-1.5-AG supply normally provides +/-12V @ 1.7A. By replacing R27 with a jumper, you can dial in -10V in addition to the +12V

Really quite simple, and the impact on my system(s) has been dramatic. No hum, and I've gotten 901s to track five octaves quite nicely.

Cheers,
Roger

Hi Roger:

What model Power One supply are you using? And are you using it in a C or P enclosure?

Sorry it wasn't clear. I use BOTH supplies mentioned in the post, in order to generate the three required voltages. One supplies the -6v line, and the other supplies the +12v and the -10v lines.

I've used the pair of supplies in a rack system and will be also installing the pair in a separate P cabinet system.

Cheers,
Roger

Roger,

Did you find the the original power supply could not be restored to original performance? You mention that you can now track more octaves, is this due to
a more stable power supply or other work that was done on your modules? I have a Moog 1C from about 1972 and I have restored my supply with new caps and checked the other components as well as the delco power transistors. The supply seems clean.

Just wondering.

Peter Lutz
[email protected]

Hi Peter,

In my case, the original supplies were not usable. But further, the performance of a 1960's era power supply, even one with properly functioning components, is simply not going to be comparable to a modern supply like the PowerOne. While I can't say whether the VCOs I have could be made to track as well with a well-tuned vintage supply, I can say that I am very happy indeed with the new supplies. Certainly, the 60 cycle hum is eliminated.

Best wishes,
Roger

Hi,
I use an original Moog 910 power supply with new caps and toroidal transformer with no issues whatsoever.
I don't think that the power supply actually dictates whether or not the 901 oscillators will track 5 octaves..?!

My 901a controllers each have a custom modification which compensates for 'scale drift' via a front panel control which either adds or subtracts a percentage of the CV voltage at any given time. It has always tracked 5 octaves.

Cheers,
Tom

Hi Tom,

Glad you were able to make the 910 power supply work for you.

Cheers,
Roger

Does anyone know how to set the two trimpots on a 909/910 Moog modular power supply? They affect the -6VDC output but both seem to interact. Not sure if one is for overvoltage or current and the other for setting the -6VDC level.

I am restoring three of these . Moog technical has refused to answer my requests for some reason.

Thanks,

Peter Lutz
Farmington, Utah
[email protected]

oakpal wrote:Does anyone know how to set the two trimpots on a 909/910 Moog modular power supply? They affect the -6VDC output but both seem to interact. Not sure if one is for overvoltage or current and the other for setting the -6VDC level.

You must have a fault there.... the two presets should adjust +12 and -6 independently.
That's what they do on mine anyway.

Cheers,
Tom