Wouldn't running just the heater, without hv help to degas?
Which reminds me why french guy stole monet...to buy degas to have his vangogh 🙂
Which reminds me why french guy stole monet...to buy degas to have his vangogh 🙂
That can lead to cathode interface building up and decreased emissions.
No, nothing that clear-cut. I do not keep failed tubes anyway, only weaker ones that still have some hope of reviving.
The regettering didn't do any harm, but the benefits were rather marginal: measurable for sure, regarding breakdown and leakage, but too weak to have an effect on real, well-designed circuits.
If an amplifier uses a 10 meg grid resistor, it could make a difference, but sensible designs are more robust than that.
Tubes tend to degrade more or less homogeneously in normal use, meaning cathode reduced emission is a very important factor, and it cannot be corrected by regettering.
Some tubes might fail predominantly due to gas, and in this case regettering could make a difference, but for regular tubes, a wider-encompassing rejuvenation process including cathode regeneration should be necessary (if at all possible)
PRR's may be the least "novel" sounding post but it's the most likely to succeed if anything will. Old HAMs have talked about this a lot. One example is third post down in this thread.
The old technique for improving emission is to run the filament voltage high by about 5-10% of the rated voltage.
In the days of “picture tubes” there were transformers sold to do this. They had a matching tube plug and socket, to make installation a simple plug in affair.
Then there was the fellow who took his tubes to the often seen “free tube tester” and didn’t bother to readjust the switches for his various tube types. Seems if you don’t readjust the filament voltage to come down to the rated voltage for each tube you can change from having something not working due to a single bad tube, to it no longer working from most of the tubes are bad.
In the days of “picture tubes” there were transformers sold to do this. They had a matching tube plug and socket, to make installation a simple plug in affair.
Then there was the fellow who took his tubes to the often seen “free tube tester” and didn’t bother to readjust the switches for his various tube types. Seems if you don’t readjust the filament voltage to come down to the rated voltage for each tube you can change from having something not working due to a single bad tube, to it no longer working from most of the tubes are bad.
That's not for gas.
More than a wee trace of gas in a CRT turns it into a fog chamber. They usually had generous getter action.
It was {as you say} for low emission. A CRT cathode has to be quite small, hard to coat, and limited heat. This was occasionally the first thing to "go bad". Boosting the heat might help for a little while.