Audio Research D400 mk2

Recently when powering up/down one of the 4 big caps under that big board arcs ( light blue)for a few seconds. The amp will power up ok and it stays on and sound great. If I just touch that area I hear a spark. I pull plug to power in/out as the switch seems to make it sound louder. Audio Research does not have caps anymore and say they will need to retrofit and replace that main board to connect to all wires , etc. under it. They say not o use it even though it powers up as normal ( less the spark, arc) for a few seconds or so.

Any thoughts as they say about 2 Grand to replace all for caps and rewire with a different board . Not including shipping.

Where's Leonard  these days as he'd have a FIT.

Thanks George ( It Still sounds Good)