Vintage Synth Repair

I'm scoping signal coming in and the buss for modulations.  Both
clean.  No matter what mod setting there is a huge pop unless I turn
the cutoff all the way down.  Even with ADSR and the rest down, if the
cutoff is up, this pop signal whose peak exceeds the ADSR's peak at
that mix node.... will emerge from the filter.  It's not showing up on
the rails.   Soo....hmm...it's kind of noisy too it seems.  So
something is probably open and it's an antenna feed to it.  It does it
more when keys are struck than trigger.  Proximity of signal to open
point I'm guessing?

Anyone else seen this before?  What a pain.  Sometimes I get these
things on ebay where..someone just plays them into the ground.  The
machine like develops 5 different problems that I'd fix...but they
just keep putting up with it until the thing totally dies.  Hehe. I
have a JUNO106 that I fixed here and the seller of course not only
didn't mention no cord came with it...he just said it stopped working.
 After i replaced the clock buffer and got itup...I found
that...ugh..it had two bad vcf/vca modules.   Or the supposedly ok
MKS30 I got that had FOUR bad ones.  I kid you not.  Anyone else have
that kind of luck?  I mean..you really learn to fix
stuff...but...someday..I'd like to make a few bucks too! :-)  -bob

PS I found another problem right away.  I'd already tried socketing
all the Transistor arrays and replacing them since I've seen them be a
problem in the past and silicon is always suspect.  But all was the
same.  So I figured something must be open and sure enough checked the
3% 1.87K resistor first and it's open. hehe. I knew that wasn't going
to be the pop though probably but it did allow me to at least scale
the filter so it sounds right and the slider doesn't respond abruptly.  

Ok...after clearing that up...it looks like (after finally digesting a
few more parts of the fuzzy diagram) that it's clean up to the inputs
of the output of the dual FET but then the filter output op amp all
the sudden has the big pop signal on it.  And I finally see that it's
a 1458 not a 301 so it could be cross talk I suppose.  Replace and
find little changed though.  With all adjusted though it's..almost
tolerable but that blasted pop when the keys are hit is still there to
where it bugs me.  I haven't worked on axxe before.  Is that just a
characteristic part of the sound? -Bob