I just made a boo-boo while testing an NOS 6SN7 on my Hickok 532 tester.
I forgot to change the filament supply selector from 12.6 volts down to 6.3
volts. I ran the tube for 1.5 - 2 min. before noticing.
After I changed the filament voltage down to 6.3 volt the tube seems to operate fine. Did I just ruin a NOS tube I wanted to use in a preamp?
Have you ever done this?
Just wondering...
TT🙁
I forgot to change the filament supply selector from 12.6 volts down to 6.3
volts. I ran the tube for 1.5 - 2 min. before noticing.
After I changed the filament voltage down to 6.3 volt the tube seems to operate fine. Did I just ruin a NOS tube I wanted to use in a preamp?
Have you ever done this?
Just wondering...
TT🙁
I've done this, sometimes just to watch what happens... Supposedly, an old trick used by the plug-on CRT "enhancers" they used to sell in the back of popular electronics - which boosted the CRT filament voltage to squeeze more emissions out of the cathode. A lot easier than changing a CRT -
I've always wondered why no radios or amplifiers have this available, so you can wring out a little more life / performance out of the tubes. I assume it's because the manufacturers want to sell you tubes, after you buy the unit. I mean if GE wanted to sell lightbulbs my making them have a finite lifespan by design...
What would a guitar amp be like if you had a footswitch that boosted the 6.3V filament winding to 7.5? To just the preamp 12AX7s - or all the tubes in the amp. Hit the switch just before playing a lead and the whole amp sounds different. Click it back when done and it goes back to normal operation. I wonder what that would do and if anyone would like it.
I assume the tubes would not be hurt being periodically and temporarily run at a bit higher filament, causing a bit higher cathode emissions, hence changing the sound of the amp. It must be a bad thing, else it would have been thought of and made available by now.
I've always wondered why no radios or amplifiers have this available, so you can wring out a little more life / performance out of the tubes. I assume it's because the manufacturers want to sell you tubes, after you buy the unit. I mean if GE wanted to sell lightbulbs my making them have a finite lifespan by design...
What would a guitar amp be like if you had a footswitch that boosted the 6.3V filament winding to 7.5? To just the preamp 12AX7s - or all the tubes in the amp. Hit the switch just before playing a lead and the whole amp sounds different. Click it back when done and it goes back to normal operation. I wonder what that would do and if anyone would like it.
I assume the tubes would not be hurt being periodically and temporarily run at a bit higher filament, causing a bit higher cathode emissions, hence changing the sound of the amp. It must be a bad thing, else it would have been thought of and made available by now.
I did something like to restore a 9" B/W CRT. I ran it with only the filament active at 9 Volts for 1 hour. This
doubled the power input for the filament and when put back in operation it worked like new.
As Adason said, if the filament is intact you should be OK. You may have reduced any gas problems.
G²
12V on a 6V heater: The heater lifetime is reduced from tens of thousands of hours to about an hour. A few minutes is not necessarily fatal but is a foolish waste of good tube life.
Heater to cathode isolation will not take this ligthly, heater wire get stretched. Not healthy at all!