[sdiy] ARP 3604P Keyboard

[Bob Weigel]

So you I assume monitor the S+H gate voltage to what a FET like arp 
typically uses..and it's toggling logically?  Leaky FET otherwise or 
some impedence to somewhere that shouldn't be I'd think.

klosmon wrote:

> I'm currently trying to repair a 2600 with a 3604 keyboard -- this is 
> the first time I've dealt with one of these (always had the later 
> keyboard).
> There was apparently a catastrophic power event;  bypass caps, two 
> transistors & the opamp were dead.  Replaced all those, all other 
> transistors tested good.  Everything is now working, except that the 
> CV output drops after releasing the key.
> All three capacitors in the CV memory circuit (C6, 7 & 8) all test 
> good, but I replaced them anyway -- no help.
> Also triple-checked the circuit board traces (since these solder-trace 
> boards can suffer from rework), and it's all correct.
>
> Can anyone point me towards a solution?  Or does this type of keyboard 
> behave that way normally?
>
> Thanks.
>
> ~GMM
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