Moog Music Forum

I played phone tag with a guy for about 3 weeks to get this....glad it paid off.


It needs some cleaning, but damn it sounds good. The organ sounds great. The brass sounds awesome when it works The attack/decay and modulation controls make for same craaaaazy sexy synth sounds

When it first powers up, the VCF works, then eventually the brass sections gives out. The strings section really doesn't work either...could be an op amp, or some caps that need to be replaced. I'm gonna open it up & clean all the sliders & contacts soon with some De-Oxit. Also, the foam they used in these to protect the internal circuit turns to goop after 30 years, so I'll have fun scraping that off.

After all the cleaning I'll see what works & what doesn't & take it to a local vintage tech...figured I'd save myself some $$$ by cleaning the easy stuff first.

If anyone has cleaned the insides of one of these before & has some tips, I'm all ears.

Hey, Mr. H. O3 owner here to. I'm psyched for you.

It's a very unique instrument and there is nothing like playing a fat chord of brass section through that filter. Some of my favorite attributes of it are the String section chorus and the way that you can delay the LFO from coming in (and having it blend in smoothly). Some people say "it's crap, such and such string machine blows it away" but I say nonsense.

As for cleaning it. Mine was trashed inside, black form crap everywhere. I used alcohol on qtips all over the board and components. It's amazing how that black funk gets all crumbly and finds it's way stacked up on resistors as if it's iron filings sitting on top of a magnet.

The guy I bought mine from must have doused it with kerosene because there was all sorts of odor on it but it functions about 95% once I get it 'booted'. I used Deoxit for all of the sliders.

There's a fair amount of information here if you search for it and various schools on how to treat the sliders. Some say they should be cleaned perfectly and kept dry, others say use dielectric grease of a particular variety, some of which is not even available anymore due to environmental concerns.

All I did was to clean the board and components with alcohol best I could, then Deoxit all of the sliders. It's better than it was but not brilliant. The other thing I did was cosmetic and that was to buy a load of slider caps from Moog; the type that goes on the Murf for all of the sliders, and picked up some Moog style knobs for the mixer section and a mini knob of the same style for the master tune.

I see you have the original wood on yours; Mine was painted black by some maniac. I'm pretty hand at woodworking so do have plans to build a new case, possibly out of cherry, possibly whitewashed popular (to match my VOS). At that time, I'll mess with the sliders. One of the other guys that own one desoldered ALL of them, took them ALL apart, then cleaned them to immaculate shine with what some funky carb cleaner that I picked up at Pep Boys. I'll dig it up and post the brand name. The guy swears by it.

As you'll see, NOTHING will remove the funk from the slider bodies; what an amazing adhesive. The stuff should be put to good use (instead of evil) in some application within the Space Program : )

Anyway, enjoy the hell out of the thing, I'm a big fan of it and not alone. If you have any questions, post it here; I'm not electronic genius but will post what I know (one of the other guys actually knows quite a bit about it, just search for Opus and you'll dig up the threads; all about 3-6 months old).

I'd be more suspect of cracked soldering than bad opamps, especially on the sliders, switches and connectors.

I'm not a fan of De-oxit. I don't use it and have been fine.
I just go for "properly cleaned and lubed" and if that doesn't work, replace the sliders.

It's possible to do some mods on them too- LFO range increased, external audio ins for chorus and vcf, etc.
Have fun!

Kevin Lightner wrote:I'd be more suspect of cracked soldering than bad opamps, especially on the sliders, switches and connectors.

I'm not a fan of De-oxit. I don't use it and have been fine.
I just go for "properly cleaned and lubed" and if that doesn't work, replace the sliders.

It's possible to do some mods on them too- LFO range increased, external audio ins for chorus and vcf, etc.
Have fun!

+1 on bad solder joints. Especially since stuff works for a little bit, then dies. Expansion from heat could be causing intermittent connections. As far as cleaning solutions, dunno what you think, Kevin, but in my (limited) experience working on electronics containing black foam of death, 90% isopropyl alcohol and Q-tips works well for removing it.

Thanks guys! I'm not looking forward to the black tar/foam/goop but I know it needs to be done. And yes the delay of the onset of the chorus is incredible sounding!

So scrape off the goop? Clean the board with alcohol and q tips? And some de omit in the sliders? Then see what's happening?

mhuxtable wrote: And some de omit in the sliders? Then see what's happening?

No deoxit! NEVER deoxit! A mild detergent and distilled water is fine.

I've found that certain citrus solvents work pretty good on the black goo.
DeSolvIt by OrangeSol is what I use.
Acetone will do it quicker, but will also remove the paint underneath and if it seeps to the front panel, will eat that too.

Deoxit never? I don't know.
In an emergency it might be my first choice, but not for restoration.

Kevin Lightner wrote:I've found that certain citrus solvents work pretty good on the black goo.
DeSolvIt by OrangeSol is what I use.
Acetone will do it quicker, but will also remove the paint underneath and if it seeps to the front panel, will eat that too.

Deoxit never? I don't know.
In an emergency it might be my first choice, but not for restoration.

I use Deox-id by GC electronics. They have a few varieties of Deox-id which are specific for various applications. They have silicone and non-silicone varieties, and I've always had good luck with their products in emergency situations. I wouldn't ever use Deoxit, but that's just me.

Sounds more like GC is cashing in on the "deoxing" hype.

Kevin Lightner wrote:Sounds more like GC is cashing in on the "deoxing" hype.

GC makes awesome stuff, despite the close naming of their products. The chemicals aren't as harsh in Deox-id as they are in Deoxit.

What's so bad about deoxit? Every amp tech I know uses it....

And how do you get inside the pots and sliders to spray stuff in?

mhuxtable wrote:What's so bad about deoxit? Every amp tech I know uses it....

And how do you get inside the pots and sliders to spray stuff in?

Deoxit works for amps...sometimes. I wouldn't dream of using it for silver plated contacts, for example. It depends on how far gone the pot is. The problem with sealed pots, is you have to drill a hole in the pot to spray the cleaning solution. This can cause MAJOR catastrophic failure to the pot. Shavings get in there, start moving around, and all of a sudden your resistive element is scratched to hell and not repairable. That's no good. Sliders are different, I think. Never seen a slider that couldn't be opened CAREFULLY, mind you. Though there might be sliders that can't be. I haven't looked inside too many vintage synths to be sure.

mhuxtable wrote:What's so bad about deoxit? Every amp tech I know uses it....

That's because they want you to eventually come back, over and over...

Deoxit works fine at restoring contacts, and pots. But it doesn't last indefinitely. You will innevitably have to redo it.
It is fine for emergency situations, and can last long enough. But it's not a permanent solution.

It the case of Opus 3, MG-1, or any other Moog synth from that era that used the foam of death, I've found that, more often then not, replacing all the sliders and toggle switches with new ones was a better permanent solution.

See Transplant Technology site for their complete kit for Opus 3. A little expensive, but worth it.

My two cents on it. TIFWIW

Hey mhuxtable, I found this link that might interest you...

http://preservethesound.com/2011/08/25/ ... -basement/

Thanks everyone! I've browsed through the forums here and got some good info, and thanks for that link!