[Richard[_12_]]

http://www.r-type.org/pdfs/kt88.pdf

I'm wanting to get 35W plate dissipation running unvarying DC current
through a KT88 and run it for several hours on a the tube that has not
been run for two decades. I'm hoping that this might activate the getter
and reduce some glassiness.

I'm trying to make the circuit as simple as possible.

I have access to 350V dc (not variable as it is) at 120mA max.

To get 35W plate dissipation we can have 350V x 100mA. Or lowest
voltage, 152V x 230mA (tube can pass 230mA cathode current). But max
current I have is 120mA, so that means lowest voltage is 291V x 120mA).

Is the simplest circuit to?:

Ground the grid - have static plate voltage of 350V, and adjust Vg2
voltage by placing a resistance in Vg2 circuit?

I'm looking at page 6 in the above document, top graph, and thinking if
I got Vg2 to about 100V, then Ia would be about 125mA. That's too hight,
so Vg2 would have to be lower than 100V.

This is the simplest circuit arrangement I can think of, because I don't
have arrange for grid bias, or an adjustable PSU voltage, or putting a
high-wattage resistor in series with cathode.

I don't know how to calculate Vg2 series resistance to get about 100V.

Am I on the right track - or not. :c). Thanks.

[Richard[_12_]]

On 07/10/2010 00:43, Richard wrote:
http://www.r-type.org/pdfs/kt88.pdf

I'm wanting to get 35W plate dissipation running unvarying DC current
through a KT88 and run it for several hours on a the tube that has not
been run for two decades. I'm hoping that this might activate the getter
and reduce some glassiness.

I'm trying to make the circuit as simple as possible.

I have access to 350V dc (not variable as it is) at 120mA max.

To get 35W plate dissipation we can have 350V x 100mA. Or lowest
voltage, 152V x 230mA (tube can pass 230mA cathode current). But max
current I have is 120mA, so that means lowest voltage is 291V x 120mA).

Is the simplest circuit to?:

Ground the grid - have static plate voltage of 350V, and adjust Vg2
voltage by placing a resistance in Vg2 circuit?

I'm looking at page 6 in the above document, top graph, and thinking if
I got Vg2 to about 100V, then Ia would be about 125mA. That's too hight,
so Vg2 would have to be lower than 100V.

This is the simplest circuit arrangement I can think of, because I don't
have arrange for grid bias, or an adjustable PSU voltage, or putting a
high-wattage resistor in series with cathode.

I don't know how to calculate Vg2 series resistance to get about 100V.

Am I on the right track - or not. :c). Thanks.

Or, could I just put a rheostat in series with heater circuit?

[Richard[_12_]]

On 07/10/2010 00:53, Richard wrote:

Am I on the right track - or not. :c). Thanks.

Or, could I just put a rheostat in series with heater circuit?

Oh, wait a minute, perhaps I can use a cathode bias resister to
effectively place a bias on g1.