Weird spring reverb problem

[Text_Edifice]

Hi all,

mid mix tonight my vesta-kaza spring reverb started humming and then feeding back with any input applied.

I don't really know where to start with troubleshooting as it looks like the unit feeds back when any signal is sent to the input (even if nothing's plugged in to the output). I think maybe something is oscillating (opamp maybe) but not sure.

Before I go swapping out components - has anyone had a similar problem / have any advice for trouble shooting?

[a.d.a.m. baby]

is there a schematic around??

[Text_Edifice]

That's the problem, I can't find one. I think it might be an issue with grounding as the shield on the inputs feeds into the circuit (seemingly by design) for some reason. But I can't find a schematic to check where this might be occurring.

I think next step is to just replace the various caps and look for any blown resistors / diodes.