Yes, that does sound like an opto-coupler issue. It's the P1501 chip on the
oscillator board. It looks like a 6-pin DIP chip, but it only has 5 pins and
one of those isn't connected to anything, so it really has 4 pins that are
used. Current replacements are Silonex NSL32SR3 and the Vactrol Vactec
VTL5C3, and a couple of others in the Silonex and Vactrol families. You'll
have to search the message threads to see what other people have used, or
check out the file "PC-1 opto replacement.txt" in the group files section.
Too bad there are no DIP package replacements available. All of these parts
are radial lead so you have to figure out which leads are the diode side and
what the polarity is before installing. Also, R93 usually needs to be
changed, and it might take some experimenting to figure out what value works
best.
Don Backshall
_____
From:
PolySix@yahoogroups.com [mailto:
PolySix@yahoogroups.com] On Behalf Of
Frank Carvalho
Sent: Tuesday, August 13, 2013 4:43 PM
To:
PolySix@yahoogroups.comSubject: [PolySix] P6 scaling issue
Hello
I am sure this is a classic issue, but it just happened to me now, and I
need some advice.
My P6 has not been used for a while, and since electronic equipment
should be turned on once in a while, I pulled it out to give it some
time turned on. But in the meantime it has developed an issue with the
scaling of the octaves. Every octave has become about a semitone too
wide. All the oscillators line up fine across the entire range, but the
range is just scaled wrong.
I read suggestions that it may be an issue with an opto-coupler, and if
that is the case, where is it located, and what modern day component may
replace it?
If it is something else, please give me your suggestions.
And before you ask, the battery was replaced long ago, before it got
bad.
Thanks
Frank Carvalho
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