[sdiy] sixtrak expert anyone?

[mark verbos]

Hi guys,

I have been working on a couple Sequential Sixtraks and they are making 
me crazy. One of them I have within an inch of finished. It has a little 
bit of what seems to be pitch modulation from low frequency noise when 
the oscilltors should be playing clean. It happens the same on all 
voices. I have  replaced all the power supply caps and the regulator on 
the -6.5 volt line.  I swapped the op amp and the 4049 in the mixer 
section, thinking maybe it was just low freq noise getting in the signal 
and tricking me into thinking it was pitch mod. The only thing I haven't 
tried (only because I don't have the part here) but I think it may be is 
the 4051 mux chip (U108).

The other one just lights up chaos LEDs on the panel and doesn't respond 
to any button presses. I swapped EPROMS and it didn't help. That one I 
am stumped completely on.

Any ideas?

thanks!

Mark