[sdiy] Polysix - trouble with EG Mode

[The Old Crow]

On Fri, 28 Jun 2002, Dave Magnuson wrote:

> 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.

  VCA mod(ulation) TP5 is to verify the MG output when MG->VCA is
selected.

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

  I'd check pin 3 on this IC to see if it changes state when the EG/gate 
switch is moved.  Also check continuity from this IC pin to CN05-1 
(connector 5, pin 1).  It is this signal that enables/disable ADSR action 
on the VCAs.

> 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.

  See above.  It is the VCA modulation signal from the MG (LFO) when the 
MG destination switch is set to VCA.

Crow
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