Moog Schematics/Service Manual

[quote author="Steve Jones"]I have made a scan of the PSU circuit, but I have no idea how to display it on the page here...[/quote]


Yeah, I'm not too sure of how to post something on here either. If you don't mind emailing it to me I would be very grateful! [email protected]
Thanks for all your help!

Well, I've replaced both ICs 1 and 2 and Q1 and I'm still getting +1.2v on the negative rail. I guess there is a short somewhere. The other thing I noticed before the sound failed is that sometimes the synth volume would kind of crap in and out while I was playing. Sometimes the sound would be extremely low even when I had volume all the way up and when I played with the settings (especially the patch switches) the issue would more than likely go away. I don't know if that had anything to do with the ultimate falure or not.

Another thing I've noticed is that one side of the regulator circuit puts out +18v while the other puts out -22v. Is that normal?

I checked all the switches and they seem to be operating properly. I can't seem to find any tantalum caps on this thing. Does your parts list say which caps should be tantalum?

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I have sent you an email of the PSU section, I hope it helps. I think there is at least one tantalum in there, perhaps C4?

[quote author="Steve Jones"]I have sent you an email of the PSU section, I hope it helps. I think there is at least one tantalum in there, perhaps C4?[/quote]

Thanks Steve!!!! You rock!!!! Hopefully I won't be bugging you with anymore questions.

Hey Steve, so much for not bothering you anymore... Ok. Thanks to the schematic I've been able to clarify something...I'm a moron...and other than that I've been thinking all along that the IC1 and 2 that you were referring to was the IC1 and IC2 on the Control PC board. Obviously you were really referring to the IC1 and IC2 on the main synth board.

So, after putting back all the chips that mistakenly replaced, I realized that IC1 (lm723) got bloody hot. I replaced the right IC2 and it still got hot. I'm just taking a shot in the dark here but I'm guessing that I should replace IC1. What do you think?

If IC 1 is getting hot, something is up wth the +9 V supply. If you replace it and it works don't forget to trim the + supply back to 9V with the trimmer.

[quote author="Steve Jones"]If IC 1 is getting hot, something is up wth the +9 V supply. If you replace it and it works don't forget to trim the + supply back to 9V with the trimmer.[/quote]

Yeah, its possible that I could have f'd something up when I replaced the wrong parts. I've got to order a 723 and go from there. Thanks man!

[quote author="Steve Jones"]If you have a scope, take a look on pin 6 of IC 3 and play the keys to see of there is a key control voltage there, and pin 6 of IC's 5 and 6 for gate signals.

The oscillator is IC's 8, 11,12 and 21, see if there is a waveform on any of the pins of transistor Q46.[/quote]

Ok Steve,

So I repaced a few ICs and now I have both +/- 9v. I get a gate signal at IC5 but nothing at IC3 and I replaced IC3 just for kicks. Not quite sure where to go from here. Also, I do see a saw waveform at Q46 so that checks out ok I guess.

I will scan the whole schematic for you over Christmas and send email it to you, congrats on getting the PSU working.

Steve, Thanks for doing that! Merry Christmas!

Hey Steve,

I seem to be at an impass here. Went ahead are replaced all the 741s on the main board (thinking that the wacked out votage rails more than likely damaged them.) Now I'm getting a constant signal. Its weird though because it is always on and changes when I change the patch settings but when I push one of the keys it goes away momentarly and then comes back. Any suggestions?

Thanks,

-Mike

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