Vintage Synth Repair

Hi,

every once in a while my MicroMoog all of a sudden goes out of tune. 
It happens all of a sudden and an octave is not an octave any more. 
When I hit it slightly on the side, it´s OK again, so I assume it 
might be somee loose cable ....

Maybe someone can give me a hint what to do about this, resp. where 
to look (I don´t have schematics....)

Thanks

Uwe

Hi,

I'm having some problems with my MicroMoog. When I power it up, the 
volume is very low, hardly audible. The volume knob has no effect on 
the volume at all. I can hear the notes I play, keyboard and 
Oscillators seem to work, the filter seems not to work.

After a while, suddenly the sound will appear at full level. The 
Moog will play perfectly as long as I keep it switched on.

Sometimes it can take up to 30 minutes, until the sound suddenly 
appears and it seems that the time it takes is getting longer....

At the moment I keep it switched on all the time in my studio.

Any idea which components could be faulty?

Thanks

UV

Hi UV,

Yeah, I used to work on these & it's big(ger) brother the Multimoog-both had 
nice problems with oscillators dropping out, filter/VCA issues, normally 
caused by resistor banks-they look like in-line chips & are usually blue in 
colour-they can be  a cause of a lot of heartache.
In your case, it is probably the VCA at fault, which if memory serves is a CA 
3080 -a transconductance Op-amp.-note also that sometimes  one or both of 
the 2 x diodes on the output of this device sometimes get slightly dodgy and 
can cause the problems of which you speak.If you are going to attempt repair 
of this Moog, then please take extreme care, as the PCB is of the unforgiving, 
double-print thru-hole plated type and can be a real nightmare to work on!
If you want the synth fixed or parts fitted etc, you can reach me at 
jim@....     I'm cheap'n'cheerful and if I can't fix it I 
usually can put you on to someone who can.
Hope this is of help!


Regards,


Jim

--- In vintagesynthrepair@yahoogroups.com, "uwe_vogel" <uwe_vogel@y...> 
wrote:

> Hi,
> 
> I'm having some problems with my MicroMoog. When I power it up, the 
> volume is very low, hardly audible. The volume knob has no effect on 
> the volume at all. I can hear the notes I play, keyboard and 
> Oscillators seem to work, the filter seems not to work.
> 
> After a while, suddenly the sound will appear at full level. The 
> Moog will play perfectly as long as I keep it switched on.
> 
> Sometimes it can take up to 30 minutes, until the sound suddenly 
> appears and it seems that the time it takes is getting longer....
> 
> At the moment I keep it switched on all the time in my studio.
> 
> Any idea which components could be faulty?
> 
> Thanks
> 
> UV