hi rich and ampsters,
rich wrote,
> - However, by temporarily introducing acetylene gas (C-two, H-two) into
> the envelope, the tungsten carbide layer can be restored to full emissive
> capability.
neat! i didn't know that (amongst billions of other things). but it
seems slightly beyond the capabilities of the average ham. i mean
even the average amplifier builder, who is *way above* the average
ham in technical capabilities! i wonder if it's cost effective for
any tubes other than big-ticket jobs (with handles!) i can't imagine
reconditioning 3-500's for instance.
i've got some meters and oscilloscopes and a radial saw, but i can't
imagine trying to bring a tube back to life this way! maybe rich
should have added..."don't try this at home." 8>) (that's a grin)
another thing i have, which i promised to share with the group, is
some results using the mfj250 deep-fat-fryer dummy load. i talked to
their tech support people, and they told me that 1500 watts was ok
for a while. keep the vent on the can open, and monitor the smell of
the air, the temperature of the can, and the SWR. if you smell
vapors, or if the *bottom* portion of the can starts to get hot (i.e.
uncomfortable, not just warm) then it's time to shut down and cool
off. and if you see SWR increase, the R is going up (that's the only
direction it'll go) and *any* change is premonitory to rapid failure,
so it's definitely time to cool off!!
the important thing to remember is that they really must cool down
significantly before putting the power to them again.
by the way, rich was right about the size of the resistor... it looks
like maybe a 75-watt job (in free air) but the oil makes it capable
of taking a whole lot of joules (ok, watt-seconds) until it's time to
quit. the resistor in the air-cooled 264 is considerable bigger, but
it only has air around it, so be very careful with that one!
sorry for the bandwidth, but thought it might be of interest.
73,
George T. Daughters, K6GT
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