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: Memorymoog repair
2008-08-25 by eggwheatis