Scott & John

Thanks for your comments.

Your advice about White parts availability is relevant. I note that White do not appear to making any more LC type EQs and have none of the transformer plug ins for sale. Makes me suspect that the use of inductors is no longer economic.

On the bright side, Van Ryswyck has made schematics of the earlier types available at his web site and he is happy to sell service manuals of the more recent types at a reasonable price. Would think that the inductors in these units would be pretty reliable and that the components most likely to cause trouble would be noisy pots and possibly op amps.

I would assume replacement pots should be obtainable and am wondering if anyone has tried to tweak these units by upgrading op amps.

Scott you are right about the 4200A being cut only, not passive. Got confused between this model and the 4320 which I gather is passive.

Regards
Ted