Vintage Synth Repair

Having problems getting the adsr to work properly on my Korg Delta.
No proper techs here in Iceland so I have got to fix things myself.

On a working Delta the VCO itself will have pretty long release independant of the ADSR.
I am missing this release from the VCO itself.

When I disconnect the VCO from the filter/vca board the release comes back on the VCO.
As soon as I connect the VCO to the filter/Vca the VCO release is cutoff.
Obviously this affects both the Synth and String Release as there is no signal to release.

The problem is therefore on the filter/Vca Board...is seems.
I assume its a problem with the "Release Control" signal sent to the VCO? 
On a healthy Delta I would have a nice trigger signal coming in to the Vco via the "Release Control going to the vca board-transistor-IC 324 , but on mine there is nothing?

So far I have checked the 324 ,tl 072 and the 4007 , all seem to be working properly although I am not getting the "Release Control" signal from the 324?
Can anyone tell me the function of each IC / 324 / 072 / An 6551 and the 4007 ?

I am kind of confused as to how the ADSR works on this synth , probably something to do with its "polyphonic" nature.

The envelope seems to work on the filter an the filter is working perfectly.
The noise however goes straight through the VCA without any envelope applied to it, which is strange?


Havent gotten much further so far.

If anyone could give me any pointers as to where/how to trace this properly?
I am a novice but I have a scope , the schematics and and I am eager to learn.

Its driving me slightly nuts at the moment. :P

Thanks
Arnar