Vintage Synth Repair

> i didn't even realize it but "c2" the capacitor hooked to pin 1 and 8
> of the op amp is totally broken. classic newbie move i guess. fix one
> problem and cause two more. so now i'm looking in the user manual and
> i don't see a value for that part in the parts list of board C-1. do
> you happen to know what the value of that component is?

http://en.wikipedia.org/wiki/Opamp#Class_A_gain_stage

If you're using a modern internally compensated opamp this capacitor might
not even be needed; however if you're using a LM301 like in the original it
is 30pF as indicated on the schematic. Because this is a "standard value"
as described in the wikipedia link it is probably not in the parts list.

I don't think this should cause this behaviour, though.

There are a few other points but you might first want to check out the
voltage on pin 3 and 4 of the filter module. Pin 3 is the output of the
opamp (and hence the various modulation sources), pin 4 is the cutoff
slider.
There's also a trimmer (T3) that is used to fine-tune the cutoff frequency;
if that one is completely out of range it might affect the frequency as
well.

I'm working on a Odyssey Mk3 at the moment myself.


-- 
Malte Rogacki gacki@...
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"Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you
 get no sound out of it." (ARP 2600 Owner's Manual)
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