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Using relays in high voltage circuits
Using relays in high voltage circuits
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Old 18th February 2003, 12:08 PM   #31
fdegrove is offline fdegrove  Europe
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Default TUBES ON THE RUNWAY.

Hi,

Quote:
Why would an unpressurised hold cause thermal runaway later?
Dunno really, it was the only explanation we could come up at the time.
Absolutely nothing was wrong with the amps electrically, the valves were replaced and the problem was gone.

Strange...

Cheers,
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Old 18th February 2003, 10:20 PM   #32
Sch3mat1c is offline Sch3mat1c  United States
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Only thing I can think of is the low pressure stressing the envelope less, and the changing stress wrecked the vacuum somehow...

Considering the glass is made with equal pressures on either side, and is constructed to have a constant compressive force (about 14PSI, i.e. atmospheric vs. zero), then reducing that force - but clearly not reversing it - can't possibly break the seal.

Were the getters still good before turning it on?

Tim
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Old 18th February 2003, 10:30 PM   #33
SY is offline SY  United States
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Using relays in high voltage circuits
Default Re: TUBES ON THE RUNWAY.

Quote:
Originally posted by fdegrove
Hi,



Dunno really, it was the only explanation we could come up at the time.
Absolutely nothing was wrong with the amps electrically, the valves were replaced and the problem was gone.

Strange...

Cheers,
Post hoc ergo propter hoc?

More likely the handling by the chimps working for the airline, I'd expect. Unpressurized cabins didn't seem to bother the tubes used by the Soviets in some of their avionics.
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Old 18th February 2003, 10:39 PM   #34
fdegrove is offline fdegrove  Europe
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Default PSI.

Hi,

The amps and valves were fine when they left the U.K.

Actually,what may have been the cause of the trouble is the PSU caps in the HT rails not being too happy with the sudden change in atmospheric pressure.

None of the output tubes showed any sign of leakage or air ingress whatsoever...

I think the PSU somewhat got unstable and I was left with a handful of blown fuses (a handful of sand really), endcaps of fuses molten into the partially carbonized fuseholders and a lot of those lovely RCA 6080s with at least one halve of the double triodes gone.

Don't worry too much about it though,
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