Hi, i just started back tonight on it.... After a a very expensive purchase of some CEM ic's I have all the voices working on it now. I was seriously scared off putting the new IC's in in case they died again...but I bit the bullet and all seems fine. Phew! SO now I have a fully working but seriously out of tune Memorymoog. The autotune wont tune it..too far out. I just get '0 tuned' I checked the calibration out in the manual and I found it a bit confusing... Has anyone got any tips on calibrating it? Thanks, Phil. --- On Tue, 21/10/08, gerryrdahl <gerryrdahl@...> wrote: From: gerryrdahl <gerryrdahl@yahoo.com> Subject: [vintagesynthrepair] Re: Memorymoog repair To: vintagesynthrepair@yahoogroups.com Date: Tuesday, 21 October, 2008, 4:13 AM Hi Phil, How has the Memorymoog turned out? Did the replacement CEM's and a calibration finish her up? Would like to know. Thanks. GD --- In vintagesynthrepair@ yahoogroups. com, "eggwheatis" <eggwheatis@ ...> wrote: > > Phew..I fixed the pot problem, well I think I have. > > I ended up taking every board out and going through them with a fine > toothed comb, I cleaned any surplus flux off, checked > everything.. scoped everything. I just could not find it. > > Then something occured to me..like many things do when repairing > stuff!..on the schematics there is an LF351 op-amp on the output of > the DAC..but it the actual socket was a TL071 which should be fine, > and i had already swapped it out..anyway it is an equivalent and is > even mentioned in parenthesis on the parts sheet next to LF351, as is > TL072 as an equivalent for LF353. In fact my memorymoog has TL072'a > and TL)71's throughout. > > Now I know how sensitive digital circuits are to 'equivalents' so I > put in an LF351 and bingo....it was fixed! Or so I thought basically > I did it again once after playing around with it after an hour..now > normally it did it every 30 seconds so it is 99% better and hasn't > done it again. > > Maybe the DAC is faulty itself but I still don't understand how this > would effect the displayed pot values. Surely that's down to the A/D? > > Also with good news comes bad...after fixing that problem I rechecked > the voices..I had lost another voice! AFter finding another red hot > regulator on a voice board I found all three CEM3340's were shorted!! > Arggh!! I was feeling pretty sick considering how expensive they are! > > I must have shorted something out while trying to fix the pot > problem...oh well.. > > So anyway I've got 5 CEM3340's on the way(one spare), a 3310 and a > 3360. After calibration that should be it. Fingers crossed X > > > --- In vintagesynthrepair@ yahoogroups. com, "eggwheatis" > <eggwheatis@ > wrote: > > > > Well this (hopefully)last problem is proving to be really difficult > > to solve. It wasnt the Zener even though it was bad. It acts as a > > regulator for the +10 vdc to the DAC from the Control boards... It > > was causing it to sit at 11.5 vdc. Changing it did nothing. > > > > It's one of those niggling annoying problems that seems to be > > undetectable. ..its driving me nuts..I'll try to explain it better. > > > > Basically you turn a pot on this synth and the pots value is shown > on > > the alpha/dec LED display, you turn the second pot the display > > instantly shows that pots value..so far so good...but after a few > > turns of various pots, it will stick on a value and won't change > with > > the new pot movements, pressing buttons, turning other pots wont > get > > rid of it(you can see the correct values flickering behind > it)..even > > turning it on and off. You have to go back and find the pot thats > got > > the value 'stuck'. Zero that pot and it's fine again. It's totally > > random and depends on the combination of pots and values. The > actual > > sound itself changes fine with the pot movement. It's just the > > displaying of the values that is a bit screwed. > > > > Remember is the physical displaying of the values that gets stuck, > > not the actual values that control the analogue parameters. They > are > > working fine. > > > > If anyone can help I'd really appreciate it, the schems are here: > > http://www.matrixsy nth.com/blog/ media/Moog/ MemorymoogSchema tics/ > > > > The service manual is here: > > http://www.retrosyn th.com/docs/ memorymoog/ mm_service. pdf > > > > Apart from this fault..it seems to be almost fixed. > > > > Thanks, Phil. > > > > > > > > > > > > > > > > > > > > > > --- In vintagesynthrepair@ yahoogroups. com, "eggwheatis" > > <eggwheatis@ > wrote: > > > > > > A bit more fixed..:o) > > > > > > well actually diagnosed.. > > > > > > The reason all the voices were dead on one card was because a > > > CEM3340 VCO chip was shorted, this pulled down the 7905 regulator > > > that sits on the edge of each voice card killing the supply to > the > > > other CEM's. I found that a CEM3360 VCA chip was also dead on the > > > same card. So after swapping a few CEM's around I know have just > > one > > > Oscillator 3 down. > > > > > > After that I noticed the VCF adsr wasnt working on one voice. A > > > quick look at the schems revealed it is generated by a CEM3310 on > > > the contour generator board. Sure enough I found the 3310 was > dead. > > > > > > So that, on the face of it, appears to be the voices sorted out. > Im > > > sure I'll find more problems. > > > > > > The synth is still totally out of tune, so it will need full > > > calibration. I'm not going to try that until I have located all > the > > > CEM chips I need. > > > > > > I also swapped all the HC ic's out for the correct LS versions > and > > > anything that isnt specified in the parts list. For instance a > lot > > > of the op amps are 1458's, the schematics and parts list specify > > > 4558. The manual also has an addition saying you should swap any > > > found to 4558. The 4558 is apparently superior. > > > > > > I still have the problem with the displayed pot values, I talked > > > about in an earlier post(below). It drove me mad..I checked out > the > > > whole of the POTPOS circuit, the MUX circuit..the display > > > circuits.... eventually after forgetting theory, schematics and > just > > > randomly testing things, I found CR1 to be open on the DMUX > board! > > > It's a 6.2 Zener..I avent changed it yet as I was going out..but > > > after checking the schems I reckon I might have solved it..it's > not > > > mentioned in the service manual, and it's right on the edge of > the > > > schems.. > > > > > > Thats it for now..Phil. > > > > > > > > > > > > > > > > > > > > > > > > > > > --- In vintagesynthrepair@ yahoogroups. com, "eggwheatis" > > > <eggwheatis@ > wrote: > > > > > > > > Fixed the hopeless switch matrix :o) there was a ribbon cable > > > plugged > > > > in the wrong way round into the common analogue board! Large > > > repairer > > > > error #5..... > > > > > > > > So now all the button functions work properly and I have > > > Oscillator 3 > > > > back!... although only 4 voices working. > > > > > > > > I also changed 4 of the hc138's to LS138's and the filter has > now > > > > started tracking the keyboard properly...I discovered two > HC377's > > > on > > > > the digital board too..they should be LS variants again... > > > > > > > > So basically im left with OSC 1,2 and 3 not working on the same > > > voice > > > > card(3 dead cem3340's on the same card surely not? I hope) OSC > 3 > > > dead > > > > on one other card. Hopeless autotune '0 tuned' all out of tune > > > with > > > > each other even on the same cards... > > > > > > > > Oh and the weird pot problem: when you > > > > move the pots the numbers in the alpha display move up and down > > > which > > > > is correct, however say you turn one pot and move to another, > > > > well the first pots status doesn't clear from the display, it's > > > > stuck there, you can see it flicker as you move the other pot > but > > > > it's stuck there unless you go back and zero the original pot. > > > Only > > > > a few pots seem to cause this problem. > > > > > > > > I reckon swapping out those wrong HC ic's will cure > that..maybe. . > > > > > > > > Im sure I'll find more problems too. It's amazing how 'previous > > > > repairer error' can completely disable a synth that probably > only > > > had > > > > a couple of faults to start with. > > > > > > > > Getting there... > > > > > > > > > > > > > > > > --- In vintagesynthrepair@ yahoogroups. com, "eggwheatis" > > > > <eggwheatis@ > wrote: > > > > > > > > > > Well ive now got sound out of it :o) this is going to be fun > > > > > though...yet again someones been in this before me that looks > > > like > > > > > they weren't on the ball. All the IC are in sockets...but > most > > > of > > > > > them have been replaced sometimes with the wrong variant. > > > > > > > > > > No sound was indeed caused by the PSU....an electrolytic > > > capacitor > > > > in > > > > > the +15 circuit on the DMUX board was put in backwards. > > Repairer > > > > > error #1. > > > > > > > > > > I thought I'd start by fixing the LED's on the left hand > control > > > > (LHC) > > > > > board and the missing digit in the alpha display so I could > see > > > > what > > > > > was going on better... > > > > > > > > > > The dead/stuck on LED's were caused by one of the legs of the > > > ls378 > > > > > at U8 on the LHC board being bent under itself in the socket. > > > > > Repairer error #2. > > > > > > > > > > The dead digit in the alpha display was caused by a dead > output > > > on > > > > > the LS273 at U1 on the LHC board. > > > > > > > > > > Anyway so now I can see and hear whats going on I have a > whole > > > host > > > > > of new problems :o) > > > > > > > > > > I have no Oscillator 3 at all across the board, Osc 1 and 2 > > also > > > > dont > > > > > work on one voice. None of the oscillators will auto-tune, i > > get > > > > > the '0 tuned message'. The filter self oscillates but wont > > track > > > > the > > > > > keyboard. > > > > > > > > > > The switch matrix is hopeless on the LHC board, buttons > > activate > > > > > wrong functions basically, the appegiator doesnt work nor > does > > > the > > > > > hold function... > > > > > > > > > > Things I can see right off the bat but need to get spares to > > fix > > > > are: > > > > > All the 74ls138's on the digital board have been replaced > with > > > HC > > > > > Cmos variants...not a good idea, these are not compatible > with > > > TTL > > > > in > > > > > most cases, so i would think they are causing a lot of > problems > > > > > (fingers crossed). You need LS in there or HCT at least.. > > > Repairer > > > > > Error #3 > > > > > > > > > > Also there is a TL071 missing out of a socket on the DMUX > > > > board..this > > > > > is connected to the auto tune circuit..buffers one of the > > > outputs I > > > > > think. Repairer Error #4 > > > > > > > > > > All in all a lot of fun! > > > > > > > > > > Phil. > > > > > > > > > > > > > > > > > > > > > > > > > --- In vintagesynthrepair@ yahoogroups. com, Philip > <eggwheatis@ > > > > > > wrote: > > > > > > > > > > > > I just got a broken Memorymoog. It's really clean, near > mint > > > in > > > > > fact, but not working. Half the reason I bought it is because > I > > > > like > > > > > a challenge :o) ..I haven't even opened it up yet so I > thought > > > I'd > > > > > post up the problems to see if anyone has an idea. > > > > > >  > > > > > > It boots up ok, but makes very little sound the most you > get > > > out > > > > of > > > > > it is a thump or slight squeak when you hit a key, the same > > > pitch > > > > > wherever you hit. The digital side seem to be mostly working. > > > > > >  > > > > > > If you hit autotune it comes back with '0 tuned' so it > can't > > > tune > > > > > any of the oscillators probably because it cant 'hear' them > so > > > to > > > > > speak. > > > > > >  > > > > > > First thoughts are some kind of DAC problem. > > > > > >  > > > > > > 2: All the LED's on the left hand side don't work at all > but > > > the > > > > > buttons do. A few are just stuck on all the time, again the > > > buttons > > > > > work. > > > > > >  > > > > > > 3: one digit on the alpha/numeric display is barely visible. > > > > > >  > > > > > > 4: this is a slightly weird one which is hard to describe, > > > when > > > > you > > > > > move the pots the numbers in the alpha display move up and > down > > > > which > > > > > is correct., however say you turn one pot and move to > another, > > > > > well the first pots status doesn't clear from the display, > > it's > > > > > stuck there, you can see it flicker as you move the other pot > > > but > > > > > it's stuck there unless you go back and zero the original > pot. > > > > Only > > > > > a few pots seem to cause this problem. > > > > > >  > > > > > > Any ideas would be helpful. Obviously the first thing im > > going > > > to > > > > > check is the PSU when I open it up later. > > > > > >  > > > > > > Thanks, Phil. > > > > > >  > > > > > > > > > > > > Send instant messages to your online friends > > > > > http://uk.messenger .yahoo.com > > > > > > > > > > > > > > > > > > > > >
Message
Re: [vintagesynthrepair] Re: Memorymoog repair
2008-10-31 by Philip