Memorymoog Power Supply woes (solved)

[zaiusz]

BAHH. So, I just plugged it in and could play it. Everything seemed ok EXCEPT the smell got bad and then I started to hear a tell tale hum creep up that is usually the 'about to explode' warning. Had to turn it off. Honestly don't know what could be wrong. Seems like it should be fine given that everything appears to operate properly otherwise. I wish I knew someone with a thermal scanner. Would still like to know about the mA measurement if anyone could explain if I'm doing something wrong. Any help much appreciated!! I feel like I'm so close at this point!

[electrojoe]

Hello,
O.K., Sounds like you may need to double check the polarity on the Caps.
You may have one backwards and that's what is cooking, and now that you have a hum, that's the first thing I would check.

Also when measuring current you need to run your Amp meter in series with the power rail you are testing.
For example, disconnect the main 5 volt rail, connect the power supply 5 volt connection to your positive probe, and the connection to the circuit board to the negative probe.
Since you tried to measure current like voltage that would have been a short, and you probably popped the fuse in your multi meter.

And lastly, I know a very good memory moog tech, if this work starts to get out of your comfort zone.

Hope that helps.
Gerry

[noddyspuncture]

So noob moment here, I can't seem to get a reading using the mA setting on my DVM. Never had the need to use this mode before so am I right in assuming the procedure is the same as reading volts? Can't see any amps at all on the 5v rail. The other rails are inconsistent too. I tried reversing the probes and could get -.9mA on my -15 rail but the other way around its only like .03mA. Made sure my DVM is set to measure DC mA too, not in AC mode. Maybe this thing is broken, has been acting a little unusual lately.

I'm sorry but I must say that working on a Memory Moog isn't a good idea for any "noob". All you are going to do is make matters worse and then have to pay more for a tech to try and sort out... if it's actually sortable after you've finished.

Time to give up and take it to a pro methinks...!?

Cheers,
Tom

[zaiusz]

Everyone working on a MemoryMoog for their first time is a noob no? I may be self taught, but been doing this for at least 5 years with many complex synths I've restored including my Jupiter 8, 6, Prophet 10, OB8 and so many others-- the MM doesnt scare me I can manage this one but there's always something to learn in the process... Trying to pickup all the tricks as I go. Most bits I've learned were from much more experienced folks like yourselves willing to offer opinions and insight. We all started somewhere but some of us never had the fortune of a proper teacher Only started down this path because any reputable tech around here was so back logged I couldn't wait, and dove right in.

Thanks Gerry for clarifying about reading amps, I did triple check all of my capacitor orientations as they went in. Anyway, will try measuring the current drain when I have a moment.

[noddyspuncture]

Well, it's just some of the comments you made and questions you asked don't quite point to someone who should be messing around inside complicated vintage electronics... sorry, apologies if that offends...!? For example your confusion measuring current.

Someone who has restored Jupiter 8's Prophet 10's and OB8's should know some of the basics you seem to be stuck on...

[atomicsynth]

Thanks Chuck. Still considering that. ....
Any further advice to a man with his first MM experience?

Yes, throw the power supply out and replace it with the new, sorry. When that stock supply fails it takes chips out. You're risking further damage to the synth.

You can't even check the pins when the header is off without jumpers between certain pins. If you shorted any of your pass transistors to the heat sink by not placing the mica insulators properly underneath them, problems abound.

You do realize the moog schematic pin numbers need to be reversed when looking head on at the supply front hopefully. There are small errors on many of the schematics according to Heinz.

I suggest making a signal trace cable from an old test probe for use with a practice amp to see if you even have output on each voice card's U22 (the 3080 ota) and also check U20 by tracer cable and or scope. You, of course have to trigger the voice and use the C4 function to know what voice is playing in kbd mode cyclic.

When my old power supply went it killed three U22's among other failures. It's a terrible supply and does not protect the synth adequately when it fails. Heinz's supply protects the synth even if the supply itself fails plus fixes the poor stock MM reset circuit.

For the record, I don't make money off those supplies. Heinz is way too busy building supplies for the rush of orders I've sent to him to answer general inquiries so I do it for him as he's a personal friend who helped me greatly with my MM as he is an expert servicing it and other vintage polysynths. I endorse his supply because it transformed my synth.

The more you power that synth with a damaged supply you risk further damage.

You should not be smelling burn from a thin layer heatsink compound. Your burn is something else.

In the words of the master.

"Many good techs fear
the Memorymoog as the devil fears holy water.
You must go very deep inside the MMs circuits and software to see what the
moog people did. They did it in an unconventional manner, never seen with any competitor".

Heinz Weierhorst.

[zaiusz]

Well guys, pleased to report that my memorymoog is well now, the panel and screen now seems much better than it was when it worked before. Power supply sorted out, correct voltages, burning smell attributed to bad MR502's in the PS feeding the tip41s-- was overheating so much that the plastic heatsync holder started to cook. Also replaced the tip41s just in case they took some damage. My diode checker on my DVM seemed to tell me these 502's worked but apparently they didn't. My osc 1 on voice 3 was always a little out of tune but I'm going to sort that out next, then calibrate it the whole thing. Such a joy to hear my beloved memorymoog again.

[megavoice]

..................."Many good techs fearthe Memorymoog as the devil fears holy water.
You must go very deep inside the MMs circuits and software to see what the
moog people did. They did it in an unconventional manner, never seen with any competitor".

Heinz Weierhorst.

Even for Heinz the MM is the biggest nightmare man can imagine. Only the old Korg PS series he refused completely even to take a look inside, The electronics and wirings could be defined with a German term "Kraut und Rüben". That means: "higledy piggledy". Direct translated it means: herb and beets.........
So this is one of the reasons he`s SO HAPPY not having the duty to work on MMs any more professionally.......

BTW, am I the single one who`s not allowed to send you private messages any more ?
Apologizes of corse if you did it for everyone. And I don`t want to know of course politely the reason why..........

[atomicsynth]

..................."Many good techs fearthe Memorymoog as the devil fears holy water.
You must go very deep inside the MMs circuits and software to see what the
moog people did. They did it in an unconventional manner, never seen with any competitor".

Heinz Weierhorst.

Even for Heinz the MM is the biggest nightmare man can imagine. Only the old Korg PS series he refused completely even to take a look inside, The electronics and wirings could be defined with a German term "Kraut und Rüben". That means: "higledy piggledy". Direct translated it means: herb and beets.........
So this is one of the reasons he`s SO HAPPY not having the duty to work on MMs any more professionally.......

BTW, am I the single one who`s not allowed to send you private messages any more ?
Apologizes of corse if you did it for everyone. And I don`t want to know of course politely the reason why..........

Megavoice, to answer your question regarding PM's I turned them off globally because I don't frequent forums enough and I don't like the pm interface here which is why my Gmail is public so I can assist Heinz.

Having spent months with Heinz in email, as you know, Heinz knows every aspect of the Memorymoog, the numerous schematic errors, failures such as the no longer avaiable Beckman array that qualifies for the synth (so he made his own new arrays from potted precision resistors), the Moog design flawed reset circuit (which is why he designed reset circuit control and protection into the supply.which totally protects the synth and eliminates Moog's vulnerabilities).
You also know he designed mods to the voice cards to achieve true tuning stability which I installed and can quite attest to).

So, again, "politely" I have gmail rather than PM.

Take care

[megavoice]

Chuck,

I cannot see clear what you mean with "Take Care" ??? I just simply wanted to know about your blocking, nothing more. I didn`t want to provoke you.
But thank you for claryfing. I feel relieved.

Also thank you about your details about Heinz`modifications, but there are A LOT more he keeps secretly, and he told me them all, and I`m of course not allowed to talk about.
But sooner or later the day will come and all that things will be revealed.

[zaiusz]

Well, I've been busy on my MM since I got the PS sorted out, realized I had a couple other problems I forgot about from long ago when I bought it. First problem was that the voice modulation contour generator didn't affect voice 4, looked up the schematics and it was exactly as I suspected, U45 on the contour/glide board. Popped a new 1458 in there and we are in business.

Next problem I rediscovered was the occasionally glitchy LEDs and sometimes it would do a weird random number generator freak-out. Tapping it on the bottom usually fixed it, but thought I'd see if I could fix the problem now since something must be loose. I noticed I could duplicate the problem when it was open and on by moving the wiring harness. I noticed P63 looked bent down a little further than normal, so I removed the RSC board and inspected the solder... found multiple broken spots. Fixed that and a few of the switches that were harder to press, put it back together and things are really looking good now.

While I was browsing my service manual page 151 I noticed something that kind of saddens me, it mentions that certain serial range of MM's had bad batches of CEM3340's with a date code of 8226 -- all these CEMs must be replaced. ALL of my CEMs have this date code(mine was a later conversion to + and must have changed to a higher SN after the upgrade), but the good news is they are all holding up still except voice 3... really hoping that once I get to calibration stage this will be remedied. I swapped two around and the problem stayed on the voice so maybe I'll be in luck.

****EDIT for closure- fixed the untunable voices by rotating the range and scale trimmers. Calibrated it all, sounds wonderful. I highly recommend using a tuner (I used the tuner in Ableton Live, it has a hz setting) rather than the software tuning program. Much easier and great results.

[Markyboard]

Hi all-
Does anyone know how much current the +5V RAW draws? This is the power signal used to drive the front panel displays and LEDs.
BTW the schematic shows 142mA but the service manual on page 121 indicate average 800 mA.

Thanks - Mark