Thanks Peter. I just soldered in the new bridge rectifier you recommended and the issue is resolved! My VH4 is back in business and sounds better than ever.
A rundown of what I experienced if anyone ends up in a similar situation:
I was playing the amp and all sound cut out instantly, leaving the amp silent. I could hear a very slight humming from the transformers if I put my ear very close to the amp. The LEDs on the front all responded as if the amp were working fine (nothing flashed, the channels seemed to switch, mute engaged, etc). The lights did not flash or do anything strange when the problem occurred. I tried switching the power tubes and preamp tubes with a set that worked in my other amps but the problem remained. I took the amp out of the chassis to inspect for anything visually wrong but didn't notice any burned out components. I checked all of the fuses (inside and outside the chassis) but they all worked fine. However, the preamp tubes were not heating up, and they were loose in their sockets. I re-tensioned the sockets but the problem persisted. Peter then correctly diagnosed the bridge rectifier as the culprit (awesome customer service!).
I think that the loose preamp sockets caused the bridge rectifier failure. I now know to be much more diligent in ensuring a tight preamp tube fit.
Thanks again.
