1970 Ampeg SVT Troubleshooting Help

[Tom Phillips]

I restored the ground connection back to the ext amp jack and now everything is normal and the 600+ VDC potential is gone from the chassis. Was wondering is there a voltage tolerance specification and what is it? I'm going to buy and install a cap kit next, then power tubes.

Glad the errant voltage reading is fixed. However, note that there was not 600+ volts on the chassis. You were measuring that voltage with respect to chassis ground. The cathodes floated up to B+ because of the missing ground connection.

The B+ voltage reading can vary quite a bit. I have measured from the low 600's to the mid 700's. I know of no official spec. Usually manufacturers put a not on the schematic telling the conditions under which the posted readings were taken and then give a tolerance. (Often 10 to 20%). However, I don't see that note on my old Ampeg SVT schematic or the one you linked.