[sdiy] Siel DK 600 voice problem (ssm2056 ?)

[cs e]

Hello

So my wife picked up a Siel DK 600 for me at a local thrift store
($10)...nice girl.  Anyways, it was dead; 4 hours later I brought it
back to life!  I'm really liking how it sounds...and I haven't played
an analog poly for quite a while.

But, Voice 2 is not behaving so nicely.  The basic problem is - the
ADSR settings don't effect Voice 2 VCA.  For example, attack does
nothing (fast attack all the time), no decay, and release does nothing
(no release - unless release set to FULL - then it's kind of a
distorted drone).  If SUSTAIN = 0, the voice doesn't sound.

Anyone have advice for troubleshooting this?  The envelope is an
SSM2056.  Does it seem like the envelope IC is dead or maybe some
associated component is bad?

Thanks
Chris