Vintage Synth Repair

That sounds great!
I know the feeling of repairing someone elses repair.
It can be madning!

Sounds like you are well on your way.
The rom version you have I believe is 1.6.

This is the pre "autotune update" version.
Some folks say this is the more desirable version.

Let us know how the final tuning goes.
GD

--- In vintagesynthrepair@yahoogroups.com, "eggwheatis" 
<eggwheatis@...> wrote:
>
> 
> 
> 
> --- In vintagesynthrepair@yahoogroups.com, Philip <eggwheatis@> 
> wrote:
> I found it. Connector P28 was plugged in backwards on the Common 
> Analogue board. :o)
> 
> Dare I say it's almost 100% fixed??
> 
> Just got to tune the filters tomorrow!
> 
> Thanks, Phil.
> 
> 
> > The problem is when you go into MONO mode, the filter stops 
> tracking across the keyboard. The 1/3 and 2/3 KB Tracking buttons 
in 
> the filter section have no effect. It's tracks ok in polyphonic 
mode.
> > Â 
> > Also in Poly mode switching the 2/3 KB Tracking button on in the 
> filter section makes the third oscillator drop almost one octave 
> across all 6 voices.
> > 
> > So what do you reckon? 
> > 
> > Thanks< phil.
> > 
> > 
> > Â 
> > Â 
> > Â 
> > 
> > 
> > --- On Sat, 1/11/08, gerryrdahl <gerryrdahl@> wrote:
> > 
> > From: gerryrdahl <gerryrdahl@>
> > Subject: [vintagesynthrepair] Re: Memorymoog repair
> > To: vintagesynthrepair@yahoogroups.com
> > Date: Saturday, 1 November, 2008, 12:50 PM
> > 
> > 
> > 
> > 
> > 
> > 
> > Hi Phil,
> > What are the readouts for the Osc's?
> > When you press c-7-enter-enter- 1-1, what does the display read?
> > If it reads dead osc or LOW, check the others and see what
> > you get.
> > You may have a CTC osc scanning problem, where the CTC cannot 
> > count (or check the tuning) on the osc's.
> > 
> > Also what version firmware do you have?
> > When you do a c-0-enter all the leds blink, in the patch readout
> > will be a flashing number, this is the version.
> > 
> > Also check the pitch bend and fine tune circuit.
> > These are supposed to be disabled during autotune. if not
> > then the MM will not tune.
> > 
> > Let us know.
> > GD
> > 
> > --- In vintagesynthrepair@ yahoogroups. com, Philip 
> <eggwheatis@ ...> 
> > wrote:
> > >
> > > 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@ ...>
> > > 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
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>