Just as a follow up you might be interested to know that I managed to
resolve my problem. I was very suspicious of the comparator IC6 being
swung over at -15V, so I ordered a new one. Whilst I was desolering
the old chip I very carefully checked all the tracks to make sure
none were broke. Oops! Track 2 was disconnected. A socket, the new
LM393N and a wire link were fitted and now all is well!
However, I still have the issue of a 'croaky' voice, a la one VCF
chip which I can move around the KLM-366 by substitution. Now where
am I going to find a another SSM 2044?!
Cheers,
Andy
--- In PolySix@yahoogroups.com, "Andrew Jury" <andy@...> wrote:
>
> Hi,
>
> Here's a nasty KLM-367 problem which has been sitting on the bench
> for the last couple of days, whilst I scratch my head. I repaired
the
> board orginally after the battery blew up a couple of years back.
All
> worked find until the a couple of weeks back when I lost control of
> the patch banks. I redid all of the wire links, but same problem.
> Eventually I found that the clock source was missing. X1 has
sheared
> off a leg so I replaced it with a 6Mhz ceramic resonator. Now the
> patch bank switches all function corectly. I can even play my patch
> bank wav files at the thing and watch the LEDs 1-8 strobe as the
data
> is read in. However, I seem to have lost control of the VCF and EG
> settings. The octave, waveshape and sub-osc all work, which is a
> start. I picked on the attack pot through to pin 4 on IC34 to see
if
> I could work out what was going on. The output from mux IC1 on KLM-
> 370 seems to swing around 0V +/- depending on the position of the
> pot. This output feeds the non-inverting side of comparator IC6
which
> presumably sets an interrupt on T0 of the micro-controller (IC22)
to
> let it know that someone has changed one of the pot setting. This
> input is compared to the output the D-A converter IC33.
Unfortunately
> pin 1 of IC6 always remains swung one way at -15v. To make matters
> worse the output from the D-A converter never seems to change from
> 0.99v despite the database changing state. Have I still got a
> corroded or broken track somewhere? Have I got a failed D-A
> converter? Does any of this sound familar? Any thoughts or input
> would be much appreciated.
>
> Cheers,
> A
>