Memorymoog issue, help is needed.

[gencomprodukts]

Hello everyone,
Big issues on my Memorymoog+. I've tried to get help on another forum but without success, so i come to see here

1st one :
For any reason i can't use the mono mode anymore. Indeed, when i press a key it's always the same pitch (same behavior when using the hold/chord memory function).
No problem when using polyphonically, everything's fine so it's not the keybed.

Here is what i did without success :
1) checked the ribbon cables and chips to see if nothing was out of the sockets but didn't find anything
2) replaced integrated chipset 4051 on U14 (Dmux board)
3) replaced CD40174 (DMUX board).
4) replaced the MC4016B integrated circuit chip U28 on the Common Analog Board
5) tested the CV/Gate out with an external synth to see if the behavior is the same and yes it is. The gate is triggering the envelope but the CV is only triggering one pitch.

2nd one :
For any reason the Arpeggio clock (internal only) doesn't work anymore.
No problem if i use an external clock so the clock input jack is fine and no issue with the LFO (the CEM3340 is ok).
I've checked all cables for oxydation (it's ok), most of them were replaced one year ago so i don't think it could be the cause.

Does anybody could help to sort these out ? Any idea ? Please, notice that i'm a noob in electronics.

Thanks very much in advance.

[Markyboard]

Hi -

Mono/poly operation is controlled by the CPU. There are just a few functions specific to mono mode that involve separate analog circuitry; filter tracking, external CV and maybe 1 or 2 others. But for the most part the circuitry that's generates the CV (i.e. the pitch) for poly or mono is common to both modes.

Since your polyphonic mode works and the CPU responds when switching it to mono (despite the mono pitch problem) I suggest the problem is in the CPU. I recommend you do a system reset (shorting pins on the Digital Board). I had a similar problem one time, banged my head too many times before discovering that something got upset.

You'll need to back up your programs. Let us know what happens and we can go from there.

[gencomprodukts]

Hi Markyboard,
Thanks very much for your help and these usefull informations.
Could you please just explain how to do exactly ? Sorry but i as said i'm a noob.
Should i just remove the Z80 to the socket and place it back ?
Could you also tell me if it's the Z80 at U1 or U10 on the digital board ?
Thanks very much !

Hi -

Mono/poly operation is controlled by the CPU. There are just a few functions specific to mono mode that involve separate analog circuitry; filter tracking, external CV and maybe 1 or 2 others. But for the most part the circuitry that's generates the CV (i.e. the pitch) for poly or mono is common to both modes.

Since your polyphonic mode works and the CPU responds when switching it to mono (despite the mono pitch problem) I suggest the problem is in the CPU. I recommend you do a system reset (shorting pins on the Digital Board). I had a similar problem one time, banged my head too many times before discovering that something got upset.

You'll need to back up your programs. Let us know what happens and we can go from there.

[Markyboard]

Almost dead middle of the Digital Board is a 3 pin connector -P49 (it has no cable connected). Short pin 2 to pin 1 or pin 3 using a clip lead or similar. Do this with the power on. Just need to short for a couple of seconds. You should see all your patches initialized after that.

No need to swap parts at this point. A processor is not going to fail in such a way that gives you the symptoms you are seeing. Lets try to not guess at this point.

[gencomprodukts]

Thanks for your explanations. I see P49 but frankly i'm a bit scared to do that with the power on. I wouldn't detroy the CPU or something else on the boards (and i don't even have a clip lead at home) so don't you have another safer trick to reset the CPU ? Thank u !

[Markyboard]

Ah wait...hold off on that reset. If you already did it no problem but I see I missed something.

The mono CV goes through the transpose circuitry on the Contour Glide Board. Does your Hold function work in Poly mode? In poly mode if you hold a chord and press the hold button can you now play that chord with 1 note?

[Markyboard]

Btw we were posting at the same time so to answer your last post...

You wont hurt anything by doing that reset. You can use anything to short those pins together, even a large flat blade screw driver. Shorting all 3 pins together is fine since 2 of them are ground.

But like I said lets hold off on that for now.

[gencomprodukts]

Well, the Hold function doesn't work properly. Indeed, if i hold a chord and press the hold button i can hear the chord but can't play it with the keybed. So maybe do you have another suggestion than reseting the CPU (i'm realy afraid to do this, frankly).

I also found a strange behavior with the foot pedal section, maybe it could help : Without any wires connected to the foot pedals jacks, when i press the knob "osc 2" on the "amount 2" i can hear a modulation (sine/saw wave) at a constant speed (no matter if i use the "amount level", it's there) and the LFO rate has no effect on the speed of this modulation.
Edit : In fact it's a leak from the waveforms of vco 2, weird. Indeed, if i switch the square i will hear a square and the speed of this modulation is changing when selecting the octave switch (16'/8' etc).

[Markyboard]

Yeah, standby please. The reset won't help anyway.

[gencomprodukts]

ll right Again thank u very much for your help and time, i appreciate !

[Markyboard]

Just to confirm I assume you don't have access to an oscilloscope?

[gencomprodukts]

No i don't.

[Markyboard]

OK, just wanted to make sure. To properly isolate this to the right part you need to be able to examine some voltages. This does not look like a very difficult problem with the right tools and know how. Probably best to take it to a service tech at this point. I realize that's not what you were hoping to read. But I totally understand and can maybe help isolate it down to a few parts - so I'll continue for a bit more.

Your foot pedal problem may or may not be related to this. Can you test out a foot pedal connected to FP1 and see if you can change the pitch with it? Do this for both poly and mono.

[gencomprodukts]

All right, i understand. Unfortunately my tech is seriously ill so this why i'm trying to solve these issues by myself.
Regarding the foot pedal behavior, i've already tested both jacks inputs and no problem with an external voltage (for instance a lfo), both in Poly or Mono mode, i can change the pitch/volume/filter for FP1 and Mod Amt/osc2 for FP2 but anyway, this litle bug is not realy important. The mono issue but also arpeggio internal clock source are both issues i would try to solve.

Do you have other ways ? Earlier you talked about the Glide Circuit and as i told you the Chord memory is not working fine (i can hear the chord but can't transpose it).
The transpose button is ok. Maybe it could help ?

[Markyboard]

Based on your foot pedal inputs working I would say that your "bleed" problem is not related to this mono issue.

Also I think the LFO issue is unrelated as well - we'll get to that later.

If I had to make a guess at this point I would trying changing out U10 (4016) and then U7 (4558) on the Contour Glide board. Do one at a time - doesn't really matter which order.