ARP 2600 TZ-581 replacement?

[JWBarlow at aol.com]

In a message dated 3/7/99 6:13:29 PM, We Are As1 wrote:

> However, can you still get the keyboard to scale into an in-tune scale
(trimming
>with the Scale trimmer)?

>I wonder if maybe the S/H tracking opamp on the keyboard board was damaged
athe
>time of the incident.  Maybe it's putting out some kind of offset.  Did you
check
>there?  There's certianly not much else in the circuit that could go wrong!

Thanks Mike! 

I should've mentioned it was the monophonic keyboard. Yeah it does scale fine,
and since the tranny was what was burned out, I didn't even think to check the
op-amp "CV memory" (DOH!), but Terry M. mentioned that as well, so that's
probably the best place to look. This is also exacerbated by the fact that the
op-amp circuit is potted (strange that it's the only epoxied circuit given in
the repair manual), so I'm not sure what I can do about it other than replace
it. I actually bought one of those replacements from that place in Chicago,
MDS about 10 years ago as an impulse buy when I found I couldn't get a
replacement for my Ring Mod module. That CV memory uses an ICL 8007 CTV (?)
op-amp for the S/H.

>Second, NTE parts are notorious for being out-of-spec, overpriced, and often,
just
>plain wrong.  And conveniently, all of the electronics stores have a no-
refunds-on-active-components
>policy.  Understandable, but SHEESH!  The rule shouldn't apply to NTE parts.

I've always been so blown away by the price, it didn't occur to me that they
were just plain wrong! BTW what I used was an NTE 288 which they claim to be a
replacement for the ECG 288.

This problem never bothered me until I started getting some extra VCOs etc.
working and wanted to switch between different controllers, and switch one
controller to different voices.

Ignorance is bliss (I should know)!
Thanks again!
John Barlow