EHX Queen Triggered wah troubleshooting help needed.

[SonicVI]

I just got an old non-functional EH Queen Triggered Wah nutso cheap and need to help with troubleshooting.  

Here's the schematic before I begin with my work so far.



First off, the pedal passes signal but it's relatively weak and there's no filter sound.  Also, in on of the filter modes I get horrible oscillation with the "Q" knob (resonance) turned up mnore than a quater turn or so.
What I've done so far is:
-checked all the switches for contunuity between poles.
-replaced all electrolytic caps apart from the tantalums
-replaced all film caps
-replaced the three 4558's and LM324
-Replaced the BC239C in the power supply as it tested bad with the analyser.
-Tested all the diodes with my Atlas Peak semiconductor analyser (all ok)
-Tested the JFET's with the analyser.  All it could tell me was that they are N-channel JFETs and with lead was the Source.  The JFETs are black and white button type transistors that just have "SCOTT" printed on them. The analyser was able to distinguish them as JFETs so I'm assuming that means they are probably ok.

-If I touch my finger to the gate of Q1 or Q2 I get some filtering effect. It appears the JFETs are acting as variable resistors to control the filter cutoff frequency and my filter is altering the voltage at the gate enough to change the resistance of the JFETs. So, I'm guessing the problem is for some reason the voltage control to the JFET's is not working, but why?

-Lastly, on the schematic, there's a 22K resistor connected to pin 5 of D2.  In my unit this resistor is 8.2K and in every gut shot of this pedal I've ever seen that resistor has a big blue CTS trim pot in its place  (as seen in this pic: http://s100.photobucket.com/albums/m23/sonicvi/?action=view&current=eh_queentriggeredwah_007.jpg)   Can anybody guess the funtion of this resistor/trimpot?   Is it acting as a bias control of some sort.  I'm not clear what GND REF means as opposed to the regular ground. Should I try replacing that resistor with a trimpot?

-Other than that power is good and opamps are getting voltage,

Any help/ideas would be appreciated.

[SonicVI]

bump.  I tried the trimpot and it helped me tune out the oscillation.  Any ideas about getting the filtering to work?   Seems like the only thing left to start testing/replacing are resistors.

[SonicVI]

anyone, anyone.  ideas?

[liquids]

I can't offer much help, but this thing interests me.

The jfets as you said provide variable resistance in parallel with the resistors across them (much like in the mutron, which uses optocoupler.  That affects the filter.  With max resistance, you're filtering at very low frequencies.  Try the resistance value across the legs with the JFETs in place, and also try subbing the jfets.  No matter what the resistance should be equal or less than the resistance (160k) in parallel.  If not, you've found a problem.

[Mark Hammer]

The GND REF is the usual Vref, or somewhere around half the supply voltage (judging by the circuit built around A2, I suspect is is a little above V+/2).  Don't let the use of a different symbol throw you off.

The addition of a trimpot on the copper side is vintage E-H, though it's difficult to tell what it's for.  It would appear to go to ground, but what value is it and what op-amp is it nearest?

One thing you should certainly look for is the presence of a suitable envelope voltage on pin 14 at the output of the envelope follower.