To: "'\[*AH\]'" email@example.com,
From: "Caloroso, Michael E" CalorosoME@corning.com,
Subject: RE: [AH] MemoryMoog & PolyMoog power supply problem
Date: Tue, 16 Nov 1999 14:25:52 -0500
> I've working in a broken MemoryMoog from now and then during the last
> months. It seems to have broken the +5V part in the Power supply board, as
> there's no voltage between pins 12 and 14 at the P131 connector. I've
> changed almost all components, but still no +5V.
> Now I've bought two almost dead Polymoogs, one with the Faratron PS board
> and the other with the Moog PS board, exactly the same as the MemoryMoog
> Without have measured previously the voltages in the PolyMoog, I took the
> Moog PS board and put it in the MemoryMoog. Still no +5V between pins
> 12-14. Then I put it back in the PolyMoog and measure the voltage: there
> was no +5V !!!. I though the problem should be in the AC transformer of my
> MemoryMoog, so it has broke the two boards.
> But then, I measured the voltage in the second PolyMoog with the Faratron
> PS board and (guess what?) there was no +5V !?!?!?!?.
> So, can anybody check theirs MemoryMoogs or PolyMoogs to see if it really
> has +5V between pins 12(-) and 14(+)?. Am I doing something wrong. Do I
> have three synths with the same failure?. Are the MM and PM service manuals
> and schems wrong?
OK, all the voltages check out fine on my Memorymoog. I think you need to start looking where the secondary comes in and work your way forward from there.
But I've got good news and bad news.
The bad news is I found out that the Polymoog and Memorymoog power supply boards are *slightly* different.
The good news is that the P131 physical assignments for the power rails are *exactly* the same, albeit two unassigned pins on the Polymoog board which now have a purpose on the Memorymoog.
When you referred to P131-12 and P131-14, I initially got confused because those pins weren't for the +5v rails on my Memorymoog schematics, they were for the -15v rails. That's when I took a closer look at the Polymoog schematics.
What I've found is that Moog changed the orientation of P131; pin 1 is on the left end of the Polymoog power supply board, but pin 1 is on the *right* end on the Memorymoog. The physical assignments are the same and the component layout is the same. So if you put a Polymoog board in a Memorymoog, P131 should plug in with pin 1 of the plug aligned with pin 15 of the board. In other words, *don't* flip the connector over to get pin 1 aligned.
If I tabulate the pin assignments for both next to each other with the Polymoog P131 pin numbers flipped over, you can see the similarities and differences (note to http://www.midiwall.com/aharchivesor both next to each other with the Polymoog P131 pin numbers flipped over, you can see the similarities and differences (note to http://www.midiwall.com/aharchives users: this will read better with a non-proportional font, IE Courier New):
users: this will read better with a non-proportional font, IE Courier New):
Memorymoog Polymoog MM P131 PM P131
--------------------- --------------------- ------- -------
(+)5v Sense (+)5v Sense 1 15
(+)5v Force (+)5v Force 2 14
(+)5v Return Sense (+)5v Return Sense 3 13
(+)5v Return Force (+)5v Return Force 4 12
(+)5v Raw n/c 5 11
Secondary tap n/c 6 10
(+)15v Return Force (+)15v Return Force 7 9
(+)15v Return Sense (+)15v Return Sense 8 8
(+)15v Force (+)15v Force 9 7
(+)15v Sense (+)15v Sense 10 6
n/c n/c 11 5
(-)15v Force (-)15v Force 12 4
(-)15v Sense (-)15v Sense 13 3
(-)15v Return Force (-)15v Return Force 14 2
(-)15v Return Sense (-)15v Return Sense 15 1
I double-checked this table. "Return" is the local ground for each rail; not the convention Moog used, but it's the more common convention that's used in the electronics field. "Force" is the current supply and "Sense" is the remote voltage sense for automatic correction of connector losses. Each Force/Sense pair is a closed loop system and each pair must be terminated at some point for the power supply to work.
As for differences, two unassigned pins on the Polymoog power supply board now have a purpose on the Memorymoog. The (+)5v Raw supplies an auxiliary voltage on the Memorymoog's left side control board. The secondary tap is used by the Memorymoog's microprocessor to perform an orderly shutdown when power is turned off. When power is removed, the secondary immediately disappears but the rails are still held high by the filter caps for a short time, so the microprocessor detects the loss of secondary AC and goes to work in the few hundred milliseconds of this time period. If you don't connect this secondary, then the Memorymoog microprocessor won't run.
The other major difference is that the (+)15v and (-)15v rails are current limited to 0.75A on the Polymoog and 1.5A on the Memorymoog, but this is easily remedied. Either power supply board can safely supply 1.5A, the pass transistors are exactly the same.
To convert a Polymoog (PM) power supply for use in a Memorymoog:
1) replace C1 with 3300uf 35v electrolytic (was 1000uf)
2) replace C4 with 3300uf 35v electrolytic (was 1000uf)
3) replace R6 (current limiting resistor) with 0.33ohm 2watt (was 0.68ohm)
4) replace R17 (current limiting resistor) with 0.33ohm 2watt (was 0.68ohm)
5) connect a 20 gauge wire or bigger from the plus side of C7 to P131-11 of the PM board
6) connect a 20 gauge wire or bigger from P133-1 of the PM board to P131-10 of the PM board
I believe I was the one who told you that they were exactly the same, my apologies for that. The board layout for both schematics show the same part number. Closer examination of the service manual parts list reveal different part numbers. And I found the missing pin assignments after comparing the two. That was some detective work.
Opinions (and mistakes) expressed herein are my own and not those of my employer.