Vintage Synth Repair

Hey all.

I recently got a lovely looking D-50, but a few things were wrong..
About 13 keys were not working, which was found to be a few tracks on the keyboard pcb which had become corroded..

After fixing that, I found a rather odd problem... one side of the reverb FX would "Feedback" rather unpleasantly after a note was played..
If the reverb level was taken down, there would be no real problem.

I could live with just using the other side, but I thought I'd have a go at fixing it..

A bit of google and I found out the MB87126A IC was the reverb IC..

A good tech (Steve Jones) advised checking for any lifted pins on the surface mount IC's.. but I could not seem to find any..

While I was probing around the reveb IC with my 'el cheapo' scope I probed on Pin 7 and the reverb feedback problem vanished!!.. The reverb seemed pretty even (Left & right) and no horrible feedback.

I measured the resistance of my scope ( 1M ) and the capacitance (about 200pf) and tried to simulate that with a resistor and cap, but the problem is still there.
Does anyone have some sort of advice about how else I could simulate my scope being between pin 7 and ground?

I realise this is a 'workaround' fix, but if I can fix my D50 easily, that would be great.

Regards
Mike