unison simply four no sound

I own an origanal simply four tubes are glowing no sound any suggestions on this problem thanks

g1165704-13-2022 10:12pm

gs5556 Details Discussions Posts This discussion Message User 1,234 posts 04-14-2022 at 02:01am Copy Comment URL Report Comment Edit Delete Is there a time delay circuit that turns on the high voltage after the heater voltage? Something there could have gone bad such as a charging capacitor used as a timer.
blackdoghifi Details Discussions Posts This discussion Message User 45 posts 04-13-2022 at 11:24pm Copy Comment URL Report Comment Edit Delete Most likely a blown plate voltage fuse.
newbee Details Discussions Posts This discussion Message User 4,767 posts 04-13-2022 at 10:48pm Copy Comment URL Report Comment Edit Delete I've had similar experiences with other amps. Caused by a burned out resistor (in the bias circuit.) Something to check out if you're up to it.