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My Self-Indulgent Memorymoog Refurb Thread!!! (Long Post)


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One thing I wasn't clear on...is it all zipped up back together and working order? How's it holding up and can you give a little more (quantitative) review on things like tuning stability compared to before the upgrade, etc.

 

Well it was Dan. I actually gave it the first trial run with it back in place the last couple of days...but.... I noticed a couple of issues: Even though the internal heat and temperature fluctuation is much much less than with the old power supply, there's still enough heat from the other electronics to cause the calibration values to drift over many hours. I wanted to better compensate for this even though it still auto tuned all 6 voices after being on for 8+ hours. A bigger problem was that for certain patches I created over

the last couple of days one of the voices (out of the 6 voice cards) was sticking out like a sore thumb. I just finished troubleshooting this and found a bad CEM chip that was not putting VCF modulation on that particular voice. Completed the easy but costly fix as I further deplete my spare CEMs :pop:. So it's still on the bench but hopefully making another and more permanent appearance in my basement studio over the next day or 2. As to a comparison before all this work, I won't really know until I'm back in business for a few months. I'm keeping my fingers crossed but I think it should be well behaved for a while.

 

BTW I really appreciate everyone's interest and support with this and I'm really happy you're still around Dan (I read and appreciate your post more than you know). TBH I was concerned that most people wouldn't be into this type of discussion and happily it's seems I'm wrong. I'll continue to post on these sort of techie projects and I hope others do so as well.

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Mark, my MM produces no heat worth mentioning running Heinz's supply with the heat sink replaced by a ventilation panel. I've not run mine for 8 plus hours though at a stretch but I had it on two hours once and no appreciable heat. The supply runs hand warm.

 

As Im sure you know, chips that fail tend to run hot. Cmos and TTL Logic in particular will fail by latching and run hot.

 

Also you changed a lot of sockets and having changed seven per voice card myself, I had an errant solder pearl shorting two pins on one (it took a 7X eye loupe to see it) so if the troubles still persist, it's worth an eye loupe inspect of your work.

 

Regarding calibration, the Mod to the cards you did greatly widens the tuning range. I suggest you calibrate using the manual's scale overshoot method with any chromatic tuner ( I plug the $15 Korg into the headphone out) and forget the Hexadecimals. They're tedious and those values will inevitably drift. It's a software thing. You'll get a better tuning using overshoot, forgetting the C7 routine.

 

It is often one step forward two steps back with a Memorymoog but it's worth it because nothing touches it.

 

A particular vulnerability are the jumper wires running from the added buffer board from the Moog autotune update in the 80s.

If one of those jumpers breaks, the synth freaks out.

 

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I used a MemoryMoog while getting my OBX serviced and didn't want to give it back.

I had the Moog Lab Series Amp Stack with the long throw Clip on Horn back then and while the String Pads were pretty much the same as the OBX the stack mode was death by discrete audio.

 

 

Magnus C350 + FMR RNP + Realistic Unisphere Mic
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I used a MemoryMoog while getting my OBX serviced and didn't want to give it back.

I had the Moog Lab Series Amp Stack with the long throw Clip on Horn back then and while the String Pads were pretty much the same as the OBX the stack mode was death by discrete audio.

 

 

18 VCO's stacked in Mono mode sounding through those over driven 3080 OTA's always won. It still does.

 

 

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Mark, my MM produces no heat worth mentioning running Heinz's supply with the heat sink replaced by a ventilation panel. I've not run mine for 8 plus hours though at a stretch but I had it on two hours once and no appreciable heat. The supply runs hand warm.

 

I hear you Chuck. I don't think the heat is abnormal (and it's hard to define appreciable). It's near non-existant with the unit open but if you close it up for 30 minutes or so and then open it you'll definitely feel it on mine before it quickly dissipates. BTW that heat can not be felt from outside the unit when closed up - even at the vent panel.

 

I have heard others mention not using the tuning software but I guess I'm stubborn and trying to see how close I can get it to optimal values. The drift I'm seeing in these values is up to about 10 counts in either direction depending on which oscillator (some don't drift at all). It does not affect the sound and like I said it will still autotune. I think I've rid the boards of any shorts as I had a couple that caused some havoc before removing them. But yeah, if problems persist I'll keep that in mind.

 

Awesome Mark! You better give us some audio samples when it's officially up and running! :D

 

I was actually working on that yesterday Richie. IIRC I still owe Mike Martin audio samples from when I posted about repairs 3 years ago.

 

 

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Mark,

 

I enjoy this type of thread. much more than many topics.

 

I'll probably never own a MemoryMoog (although I have owned a Prophet 600), but I've been an electronic tech since I was 14, and am now 74.

 

At least on the older stuff, if one can find a replacement part, one can still fix it without a multiple thousand dollar soldering and magnification outfit.

Howard Grand|Hamm SK1-73|Kurz PC2|PC2X|PC3|PC3X|PC361; QSC K10's

HP DAW|Epi Les Paul & LP 5-str bass|iPad mini2

"Now faith is the substance of things hoped for, the evidence of things not seen."

Jim

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At least on the older stuff, if one can find a replacement part, one can still fix it without a multiple thousand dollar soldering and magnification outfit.

 

(I can't help but say that I don't miss Sonikmatter in the least as you remember it too).

 

Heinz's supply is all SMD and he solders it by hand with an ordinary Weller he's used for at least 30 years. His workmanship is amazing!

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Mark, my MM produces no heat worth mentioning running Heinz's supply with the heat sink replaced by a ventilation panel. I've not run mine for 8 plus hours though at a stretch but I had it on two hours once and no appreciable heat. The supply runs hand warm.

 

I hear you Chuck. I don't think the heat is abnormal (and it's hard to define appreciable). It's near non-existant with the unit open but if you close it up for 30 minutes or so and then open it you'll definitely feel it on mine before it quickly dissipates. BTW that heat can not be felt from outside the unit when closed up - even at the vent panel.

 

I have heard others mention not using the tuning software but I guess I'm stubborn and trying to see how close I can get it to optimal values. The drift I'm seeing in these values is up to about 10 counts in either direction depending on which oscillator (some don't drift at all). It does not affect the sound and like I said it will still autotune. I think I've rid the boards of any shorts as I had a couple that caused some havoc before removing them. But yeah, if problems persist I'll keep that in mind.

 

Awesome Mark! You better give us some audio samples when it's officially up and running! :D

 

I was actually working on that yesterday Richie. IIRC I still owe Mike Martin audio samples from when I posted about repairs 3 years ago.

 

 

Mark, As long as it's autotuning ( how that word has become ruined) you're ok That Hex drift is why I stopped using the C7 routine. It is a software flaw, I believe.

 

I have audio samples of mine on my instagram. Some are audio direct, others through a small desktop practice amp while I was working on it)

 

https://www.instagram.com/p/6YG_1gKQyx/

 

https://www.instagram.com/p/6EQQXxKQxr/

 

(Power supply leds glowing)

 

https://www.instagram.com/p/59H7s_qQ1o/

 

https://www.instagram.com/p/59DlaiqQwu/

 

https://www.instagram.com/p/5aha7bqQ_v/

 

https://www.instagram.com/p/7GdaJFKQ3P/

 

This is from a recording of mine in the 80's. The solo is on the same MM in Mono mode, which stacks all six voices (18 oscillators) on one note.

 

https://www.instagram.com/p/_0o3aIKQ2q/

 

_______

 

https://www.instagram.com/p/5aha7bqQ_v/

 

(Power supply led glow photo, and that glow is the only way you know it's on because there's no noise anymore as the fan is gone as it is no longer needed with Heinz's supply.

 

https://www.instagram.com/p/55B71LKQ9H/

 

Photo of Heinz''s supply which he installed into a Jupiter 8. (It also is adapted for Prophets, Chromas, Oberheims and Polymoogs, among others).

 

https://www.instagram.com/p/BACs1qvKQ0d/

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Then the rhetorical golden question,

 

Is it worth ripping out the Dmux board to check the entire commutator chain of all those caps replaced on the Moog autotune update and then the Common Analog board to chase a phantom on a vintage synth from the 80's when all six voices are tuning?

 

No.

 

Especially since mine from day 1 before and after the autotune update along with everyone else's I've ever heard of (save now for "one"...) drifts from the nominal hex and will be different on each power on plus change as the synth stays on.

 

Mine stays in pkaying tune now but again, I don't bother with or even check the software tuning routine anymore.

 

 

 

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  • 1 month later...

My 2.5 month refurb turned into 4 months. Had several problems surface soon after my last post and one was extremely difficult to troubleshoot. The grueling details are here for anyone interested in the ultra techno geekdom.

 

Anyway after much frustration I resolved not only a very difficult intermittent issue but also the excessive drift problem I reported on previously. This thing is finally stable and behaving itself. Here's a few of the patches I put together checking things out over the last couple of months.

 

Mark's Memorymoog

 

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Yeah, absolutely rock stable supply rails are job one in any analogue poly.

 

Having worked in military electronics, I learned a long time ago that ribbon cables cannot be trusted with critical voltages. That's one of the achilles heels of the MM.

 

And then many modern modulars use ribbon cable for the power buss :facepalm:

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OK- I'll throw out an almost random date of Sat, June 25 around noon. We can get the grill going and do the afternoon hang. Feel free to throw out another date if this doesn't work. Maybe best to start another thread but since you asked here...
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There's always those Ebay listings where the seller is hoping someone will bite on the absurd. Or so I thought. There's currently a bidding war going on for a Memorymoog reaching insane prices.

 

Heh... "All pots were cleaned and keyboard has been restored" does not meet my definition of "Perfect Condition Restored".

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