The amazing thing about this amp is that the owner played it out four nights a week for almost a decade, and only recently experienced issues with it.
The whole amp was covered in dust, some of the filter caps were just floating around inside the chassis (one of which had broken loose completely, leaving a bare high voltage wire to flap in the wind), gaffer's tape was used on the power cord connections (no solder), and one of the power tubes had suffered arc damage. The other unbelievable part about this amp is that almost all the old tubes tested like new!
This SVT is one of the early models that originally came outfitted with 6146 output tubes. It had been modified to accept 6550s sometime long ago. An extra transformer and rectifier had been installed to boost the screen grid voltage. From what I understand Ampeg may have sold this modification as a kit at some point - the circuit is very similar to a Delon voltage doubler circuit, pretty slick.
I cleaned everything up as best I could, installed new output tube sockets, power switches, electrolytic caps, and a few overheated/out of spec resistors. Makes 310W clean at 40Hz with a plate voltage of 710V!
