Vintage Synth Repair

Hello,

I have an Arp 2600 - grey face/white lettering/schematic symbols on 
the jacks.  It has an Arp 4072 VCF and from the looks of it, the VCF 
has been modded with additional resistors to correct the frequency 
response.  When I purchased the Arp 2600 everything worked fine, 
however, a few days ago the VCF stopped passing input or responding 
to CV.  It will not self oscillate either.  I have opened her up and 
checked the signal path in and out of the VCF.  The audio and CV all 
reach the sliders and even pass through the sliders, but, that is 
where the signal dies.  I followed the signal path of the CV input 
and found it alive on the 4072 submodule.  I have read many lists and 
know people say the op amps in the Arp 2600 are garbage and need to 
be replaced.  Does the 4072 VCF have these op amps?  I was also 
wondering if it could be the summing amp for the audio input mixer to 
the VCF.  This exhausts my trouble shooting knowledge of an Arp 
2600.  I'm hoping someone has experience with this type of problem 
and can direct me toward some possible solutions.  I am also 
considering replacing the power supply and was wondering if anybody 
knows of a good power supply to use.

Thanks in advance,

Ethan