Phono preamp hum


I have a inexpensive Bellari phonostage that sounds pretty good after a 15 minute warmup, but develops a terrific hum after about 30 minutes.  It has one tube.  Anyone have an idea?

boxcarman

I’m sure it’s an easy fix. But the fixer needs physical access to the unit.

I’ve had a bad tube behave like that in the past…I replaced the tube, and never heard it again.

It's equally possible that by removing and replacing the tube, in your scenario, you improved contact at one or another tube pins, thereby curing hum that had nothing to do with the tube itself.