I put this subject in quotation marks because I've been scolded by others that no such thing exists, at least by that name.

The theory is that when B+ is applied to a tube before its filament/heater is hot, the plate voltage will strip (electrons) (cathode coating), pick one, out of the cathode, and poison the rest of the tube or ruin the cathode.

If you Google "Cathode Stripping," you will find various conflicting theories. One says that below 10kV (or is it 1kV?), it can't occur. Others caution that you should switch hi-fi amps to "standby" (cutting off B+ to the plates) before turning the amp ON, and then wait a minute after turning on the power to the filaments before switching the B+ on.

Another web source says that when powering down a hi-fi amp, turn off the amp, wait a minute to allow the B+ to discharge, and then turn off the standby switch.

I am unable to find any reference to this issue in "Radiotron Designer's Handbook," 4th ed.

This much is sure: many hi-fi tube-type amps have a "standby" switch.

Help me understand this!

Hi Doug

This might be related. Before a tube warms up with B+ on the plate I've seen sparks in the cathode coating. Eventually enough cathode coating falls off to see white particles inside a tube. This cause reduced emission. (Look at some of your used tubes. They will have white flakes,)

Norm

:I put this subject in quotation marks because I've been scolded by others that no such thing exists, at least by that name.
:
:The theory is that when B+ is applied to a tube before its filament/heater is hot, the plate voltage will strip (electrons) (cathode coating), pick one, out of the cathode, and poison the rest of the tube or ruin the cathode.
:
:If you Google "Cathode Stripping," you will find various conflicting theories. One says that below 10kV (or is it 1kV?), it can't occur. Others caution that you should switch hi-fi amps to "standby" (cutting off B+ to the plates) before turning the amp ON, and then wait a minute after turning on the power to the filaments before switching the B+ on.
:
:Another web source says that when powering down a hi-fi amp, turn off the amp, wait a minute to allow the B+ to discharge, and then turn off the standby switch.
:
:I am unable to find any reference to this issue in "Radiotron Designer's Handbook," 4th ed.
:
:This much is sure: many hi-fi tube-type amps have a "standby" switch.
:
:Help me understand this!

Yeah. When I want to rejuvenate a coated cathode tube, I apply high voltage and run the filament higher than normal. Then, I dim it down and the sparks begin to happen. Sometimes it helps. Sometimes it doesn't. Usually, if it does help things, the tube only lasts a while and then gets weak again.

T.