[sdiy] Polysix - trouble with EG Mode

[Dave Magnuson]

Hi List,

I know there's a couple Polysix gurus on the list... and I have a question
for you:

I'm fixing a friend's Polysix... it had terrible corrosion problems from
the battery.  I've put in about 50 hours of labor repairing traces,
changing the battery, and locating 2 dead LM13600 and 1 dead 74LS08.  Now
almost everything seems to be working again except the "EG mode" switch.
The VCAs seem to be stuck in "gate" mode, and won't respond to the envelope
generator.

I noticed TP5 on the KLM-367 (processor/battery) board is listed as "VCA
Mode" on the silkscreen.  When checking this with a DVM or oscilliscope I
see no change when flipping the switch...  that point always remains at 0V.

I've checked continuity of the "D02" and "P10" lines and they both check
out fine throughout the synth.  These are the data lines that connect to
the two sides of the EG mode switch.  I also verified that D4 on KLM-369
board is ok.

I'm guessing that IC34 (14042) on the KLM-367 is dead.  Does this seem like
the culprit to you PS6 gurus?

Also, what should I see on KLM-367, TP5?  I'm curious what to expect on the
VCA mode connection when the synth is working properly.  I couldn't find
any mention of this test point on the calibration/setup instructions.

Thanks in advance!!

Dave Magnuson

Resonant Frequency:
resfreq at hoohahrecords.com
http://www.hoohahrecords.com/resfreq/index.html