SH-1000 LFO

[Johan Gustavsson]

Hi all!

Just a little problem I have:

My SH-1000 isn't feeling very well. Or rather, most parts of it are,
but the saw LFO isn't, and with that neither is the random note
features and some other stuff. Neither is the filter working very
well, but that might have something to do with the strange CVs put out
by the LFO section. Anyway, I've been measuring around a bit and it
seems that the culprit really is the LFO section - up to that point
everything works as it should, and the LFO gets all it's supply
voltages, but it doesn't oscillate.

The LFO on the SH-1000 is built with three normal transistors, one FET
and one weird thingie which looks like a tranny, but has the symbol of
a diode with three legs (?) and a bunch of resistors, caps and a
diode. Anyway, the first and last tranny i believe to be some sort of
buffers, so inbetween them there's one normal transistor, then comes
the three-legged diode thing, then comes the FET (which I suppose works
as a voltage control element of some kind, since the CV from the
"Rate" panel pot is injected somewhere around there). I don't really
know how this is supposed to work - I've been looking around LFO
circuits on the web, but most modern circuits tend to use opamps and
I've never seen any mutant three-legged diodes, so...Anybody out there
knows the circuit and has an explanation on what is supposed to happen
in it?

Also, could anybody direct me to a good transistor/diode replacement
source? This thing uses 2SC373 trannys and 1S1555 diodes, something
none of my parts catalogs or even replacement guides has ever heard of.

Oh, well, I'm all questions. It's a wonderful summers day here in
Sweden, I can tell you, so now I'm off to...work. Oh well.
/Moxie (Looking to lock himself into a stuffy office)