"The max rating for a 6AG7 is 300 V, so you ran them at 3.3 the max voltage!
It must be one tough tube. The plate dissapation is 9 watts"
The maximum plate voltage for the 6AG7 in grid driven configuration is 300
volts. Grounded grid configuration is quite different. I know of no
published ratings for that, but it was obvious that the 1,000 volts did not
exceed their ability - because they ran for an extended period of time and
were still putting out what appeared to be the same power as when I started.
The tube shells are not discolored. Although I have heard stories of
inverting them and running them in either oil or water, I did neither. I
did not have a fan on them.
The tubes were free, I was poor, and I wanted to push the envelope (tube).
While my friends in high school were driving 80 mph on windy roads, or
riding motorcycles, my pushing the envelope simply involved running 4 tubes
in a manner not specified by the RCA tube manual, at a power which may have
exceeded the published plate diissipation. I survived, it survived, and I
learned a bit.
My only regret was that, since the tubes survived, I did not push the
envelope far enough. Until you push a tube to destruction, there is still
more to be learned. I have been following rules all my life. Flying
helicopters, I must keep the rotor blades within a certain rpm range. Too
slow, and I die. Too fast and I die. Abusing those tubes to destruction
could have been my one bright spot of non-conformity. Alas, I could not
even see how red the plates were, so they were not a bright spot Every once
in awhile, I get the urge to bend the rules a bit. It usually goes away,
though.
Maybe I will get that amp out again and see what it can do.
73, Colin K7FM
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