Memorymoog tuning questions...yes...again.

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caramba
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Memorymoog tuning questions...yes...again.

Post by caramba » Sun Jun 10, 2012 6:18 pm

Hi fellow moogers.
I am performing memorymoog tuning procedure and I have some issues to deal with. Here are the basic facts: It's a no-plus model. The PSU and voltages are solid. Oxydation seems minimal ( i have cleaned and reseated most of the connectors). I have 2 voices tuned after autotune . All the VCO's are working.

Now here's what's wrong:

Voice 1 - can't tune 3rd VCO. It's out of the range's trimmer range.
Voice 2 - In some patches filter seems closed. After moving filter pot - it opens like the others. 3VCO's show "Dead OSC" but produce sound
Voice 3 -same problem as Voice 1
Voice 4 - seems to be in very high pitch - impossible to tune town with trimmers of course - it's to far up.
Voice 5 - OK
Voice 6 - OK
I would be very grateful for any pointers!!

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MC
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Re: Memorymoog tuning questions...yes...again.

Post by MC » Mon Jun 11, 2012 9:17 am

Check the CVs going to the voicecards. You could have some bad S&H circuits.
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thealien666
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Re: Memorymoog tuning questions...yes...again.

Post by thealien666 » Mon Jun 11, 2012 1:21 pm

If it hasn't been done already, you could also re-seat all the Curtis chips in their sockets.
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caramba
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Re: Memorymoog tuning questions...yes...again.

Post by caramba » Tue Jun 12, 2012 5:41 am

So here is what it was. I've noticed, that the pitch on the voice 4 is high and it does not respond to CV (keyboard) - keeps playing the same tone. So I've suspected a problem on the contour-glide board under the keyboard. I've cleaned and reseated all the connectors and one Voice 4's Curtis chip. I did not have any big hopes, but it totally fixed everything on all the voice cards! The synth could be finally tuned. Now I have 6-tuned message when the Memorymoog is cold and after it's warm. Lucky me! Thanks everyone.

PS. I am posting a full description of what happened because some people don't even when they fix the problem and that makes a thread useless for the future users.
Last edited by caramba on Wed Jun 13, 2012 8:52 am, edited 1 time in total.

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MC
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Re: Memorymoog tuning questions...yes...again.

Post by MC » Tue Jun 12, 2012 9:30 am

I have owned my MM+ since 1986 and can testify that dirty connectors were a big problem. I finally replaced selected headers on the PC board (any that are carrying critical CVs) with gold-plated equivalents in 1995. Big job but well worth it, no tuning issues since then.
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thealien666
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Re: Memorymoog tuning questions...yes...again.

Post by thealien666 » Tue Jun 12, 2012 2:14 pm

Hey caramba, I'm sure glad you were able to fix it relatively simply ! :D
And thanks for the feedback on the situation. It might sure help someone else with a MM, or any other vintage synth for that matter, as oxidized connectors and IC pins in their sockets can happen more often then not. Especially when they're not gold-plated, and even when they are it can still happen.
Moog Minimoog D (1975)
DSI OB6
DSI Prophet REV2
Oberheim Matrix-6
Ensoniq SQ-80
Korg DW8000
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LaxSlash1993
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Re: Memorymoog tuning questions...yes...again.

Post by LaxSlash1993 » Wed Jun 13, 2012 12:14 am

I'm gonna have to try that for my PITCH HI VCO problem.

I'd be curious to see if it fixes my issue with the panel as well...

Someone (MC?) suggested a bad S&H cap a while back... but reseating the Curtis Chips on the actual card itself might be worth a try.

caramba
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Re: Memorymoog tuning questions...yes...again.

Post by caramba » Wed Jun 13, 2012 9:16 am

Yeah. I was lucky. :mrgreen: Also - my MM is in great shape and has virtually no oxidation. Mind you - I'm not a tech. Just a hobbyist so it took me a while to understand how it works.
It was after I've noticed, that the voice cards on MM are not connected in parallel but in series! That means, that any problem with voltages on the first card can affect the last one for example (please correct me if I'm wrong). And they are connected like so - First F than E,D,C,B,A.
Contour-glide board - that's another story. Seems to have individual sections for each voice card.
So what I think has happened. My "first-in-harness" voice cards (F and E) were O.K. Then "D" had already hi-pitch problem. So when I've cleaned the connection between my contour-glide board and voice card D, it affected positively all following voice cards fixing all their problems! Again -please correct me if my reasoning is wrong.
It shows, how Memorymoog's parameters can be easily messed up by some stupid glitch....Scary! And you should check the signal from the beginning - not to turn the trimpots like crazy thinking, that they've oxidated or sth.... :oops:
Also - I've read a lot of crazy stories how poorly MM is built, what jungle of cables is in there etc. But (again -I'm no tech) I've found it pretty logically laid out and easy to work on...(you don't have to remove anything to make an adjustment). So it's not so bad :idea: I keep my fingers crossed however :mrgreen:
Now that I have "6 tuned" I spend my evenings playing the patches until I fall under the table. It's sooo good.....

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