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Re: Max anode voltage?

Original poster: FutureT@xxxxxxx In a message dated 5/15/06 10:34:07 PM Eastern Daylight Time, tesla@xxxxxxxxxx writes:

Hi all, in particular tube experts (yes I am talking the old big metal
glass/ceramic things with heaters)

Anybody know what the max anode voltage rating in a triode spec means?
specifically the GU5B
i.e. does it mean the maximum supply voltage or the maximum peak voltage
that is allowed on the anode.
What may happen if the maximum peak anode voltage is exceeded, assuming the
maximum anode dissipation is not exceeded.
Thanks in advance.


I don't know exactly what voltage that particular tube can handle
(ignoring the specs I mean), but I can
give my results with an 833A which is rated for 4kV max plate
voltage.  I've used a raw AC power supply of 5kVAC on the plate,
and things were OK but on the edge.  Arcs began to occur in
the tube when I tried higher voltages.  To some degree the tank
load affects how much voltage the tube can withstand.
Individual variations between tubes can affect their voltage
standoff capabilities.  In some cases I may have had too much
voltage on the grid also which may have contributed to problems.
I generally run the 833A's on 5kVAC in any case.

If a plate lead choke/resistor is used to feed the plate, this
will limit the current in the event of an arc-over and protect
the tube usually.  Still, internal arcs are not good for the tubes.
For more powerful systems, a crowbar circuit can be used to
shut down the power quickly.

I've applied about 4.5kV to an 845 tube which is rated at
1200 volts.  That too was on the edge.