Thinking about it a little more, since it may or may not have
transitioned to TX, the driver or any of the other tubes that are bias
controlled can do the same at reduced voltages.
Hope there was no long term damage.
I once worked on a FT101E that had a defective socket on the grid of
one of the finals. As soon as HV came on, with that grid floating, it
began cooking. Bias measured OK, all voltages lookedOK, but no bias was
getting to the actual tube--duh! I finally figured out what was going
on after the tube got so hot, the vacuum sucked a hole thru the side of
the tube. Still have that tube BTW...reminder..
Curt
KU8L
On 3/12/2014 12:18 PM, Damien Mannix wrote:
Hi all,
Still waiting for better weather to put up an antenna but then ready
to go with my TR4/AC4 which are fine into a dummy load, or at least
they were!
Bought a, supposedly good, AC4 as a spare. Decided to power it up
gradually with the TR4 as a load. Two hours at 50v, two at 80v, two
at 110v, two at 140v. No problems and a fan on the rear behind the PA
begins to run at this voltage. Then, ten minutes at 170v and 'wow'
what is that smell? I thought it was my shack heater.
No it was the TR4. The top, above the forward most PA tube, was
unbelievably hot. Switched off immediately of course.
Can't spot anything untoward in the PA compartment so after a complete
cool down I took it slowly up to 230v with my usual AC4. Not done a
full test but it seems perfectly happy again, heat and smell wise,
after 30 minutes at 230v.
Might I have ruined anything and, presumably, the fault is in the AC4.
Thanks in advance for any thoughts.
73
Damien G3XER
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