Turning tube amp off and back on quickly

[Dandy]

Switching tube rectified amps on and off during testing a build has cost me a couple of tube rectifiers, so I try not to do it, at least not more than necessary.

 

[Adam N.]

I toasted two rectifier tubes doing this accidentally. I am surely not an expert but I think that this also damaged the can capacitor because the can went bad after the flashing the rectifiers from hot power cycles. For what it's worth this happened because the smart switch the amp is on malfunctioned, not the actual switch but the internet support system that smart switch runs on. My attempted fix for this worked out poorly and the rectifier flashed. At that point the can cap had an intermittent short or something and the amp was making a loud hum noise at the speaker.

I replaced the can cap and all was good. I think it was about $45 for the can cap and $30 for two rectifiers. Plus there was a lot of agita on my part because I don't know diddly about electronics, but am learning, unfortunately. I actually soldered the can cap back in myself after local shops wanted the amp for weeks with big service charges.

I may be wrong but I think turning off the amp first allows incoming music to drain down the capacitors. It does prevent that "pop" sound and, I think, ameliorates, somewhat, the hot cycle problem.

The bottom line is don't hot cycle tube amps. I have no idea why you'd want to turn an amp on and off in under a couple minutes anyhow.

 

[Adam N.]

Should not be an issue if sufficient time is given before powering on again.

The current inrush limiter in tube equipment is specifically to prevent damage from the initial power surge. Damage mainly occurs when tube equipment is shut off and immediately powered on again before the thermal limiter had a chance to cool down.

So long as at least few minutes are given between powering down & powering back up again, there should not be a problem.

I use my amp this way as well. Also, tubes are really not that expensive unless you're really using some very expensive tubes. If I listen to my tube amp for 2 hours per day on average that's seven hundred hours a year more or less. I should be able to get many years of listening out of a single set of tubes. In that time I will have spent way more money on truly meaningless things. I figure that it's pennies per hour. If you lose 1,000 hours of tube life that's maybe as much as $50 spread over years of use.