To: "'\[*AH\]'" analogue@hyperreal.org,
From: "Caloroso, Michael E" CalorosoME@corning.com,
cc:
Subject: RE: [AH] My MemoryMoog is still alive! (was MemoryMoog & PolyMoog
Date: Tue, 30 Nov 1999 16:20:59 -0500
> Should this means the Z80 can be damagged easily this way? Are this CPUs still for sale? How much is a new Z80?
>
Nah, the reset pin is buffered, that wouldn't damage the CPU. Your Z80 is definitely working, you got "MOOG" to show up on the display.
> I think the voice connectors are fine. I hope the CEM3310s & 3340s are
> fine, they're too expensive!. I can check all CEMs with my OB-Xa, but I do
> preffer not to handle very much these ICs.
> One strange thing: the lfo rate led is always on, it doesn't blink at all.
> What should be the reason? I think the two leads coming from the sequencer
> board involving the lfo rate led are in the right destinations (as showed
> in the midi upgrade Factory Bulletin).
>
If you press buttons and the LEDs toggle, and you turn knobs and the numbers appear in the display then the computer is running fine. Otherwise something is locking up the CPU, that may be why the LFO rate LED is always on. As stated, the fact that "MOOG" appears tells you that the Z80 is fine, the computer may be stuck somewhere after that. Diagnosing a computer failure like this is way too difficult in this forum, you'll need a good MM tech like JL or Fred McNiff.
If the computer is OK, then you should troubleshoot the voice cards. Worry about the LFO light later. I highly recommend getting a copy of the most recent service manual, there are different editions and mine is the second edition dated March 1983, which I think is the latest version. Cary Roberts' online service manual is an older version, I don't know the differences, my attempts to print it out from Adobe Acrobat were not successful (problem with my end, not the website).
You can troubleshoot the CEMs without removing them. Start by tracing the trigger signals from the DMUX board to the contour/glide board. That will confirm if the CEM3310s are working. It will be easier to do this with all but one voice card disabled so you can follow one trigger at a time (the service manual has the details on this). The schematics are pretty well documented, I recommend full size copies 'cause the originals are big but much easier to read (original size is 24"x36").
After you confirm the CEM3310s are working, go back to the DMUX and confirm that you got a raw keyboard CV on the sample and hold output, and trace that to the voice card, it goes through two or three other boards before it makes it to the voice card, so there are plenty of places for something to go wrong. Once you see a CV at the voice card, the CEM3340 should bark. The MM won't autotune a dead voice if its CV is missing from the DMUX.
>From the CEM3340s forward it's a matter of tracing the audio signal from CEM3340 to mixer to filter to VCA to final VCA, so a scope will come in handy.
The DMUX is the source of power supply distribution and the source of all control voltages and triggers to the voice cards, so this is an important place to start.
Obviously if you don't have any trigger signals or CV voltages at the DMUX board you have to work your way back, which means working with multiplexed signals which means you need a logic analyzer and/or a good scope. At this point a trip to the tech shop would be a better option, because this would be far too difficult to diagnose in this forum.
Oh, while you're poking around it would DEFINITELY be a good idea to check power rails at each board and a sample CEM.
This is all from memory and I have email only at work, so I'm limited to the depth of detail I can provide, the service manual can reveal more info. You're making good progress now that you got the power supply working and you found the wrong connectors. Good luck.
MC
---------------------------------------------------------------------------
Got Moog?
Opinions (and mistakes) expressed herein are my own and not those of my employer.