OK, I see, Svetlana. Hmm, I wonder what the plate characteristics look like extended to 10kV. And I note the positive grid voltage (+100V, to 200mA grid current) to get 1A plate currents below 1kV. The performance curves aren't nearly as elegant as the glass tube!
I'm sure there are other transmitting tubes with higher rated plate voltages, and maybe lower max current. Probably ceramic, more rugged but not as pretty.
John
Look up any of the radar modulator tubes. The old WW2 715-ABC can handle like 3 AMPS at 20KV. At a short duty cycle of course. They're relatively cheap. Still being made under some other number IIRC.
For very low leakage inductance and have good HV insulation, use coax cable for the toroid winding, splitting the shield primary for parallel input and 1:N ratio where N is the splits.
Hello Win,
Actually I was. They are (were?) quite good ferrites. Else it's probably better to go for a huge pot core and a matching bobbin. That would be easier to wind and to keep the HV winding firmly in place. Older PC power supplies have one in there but I believe it's without bobbin.
Regards, Joerg
Hello John,
Be careful. I once built a tube RF amp and being a student it had to be ultra low budget. So I let the finals have about 50% higher plate voltage than their data sheet said. One of them arced over. Big blue flash. That took the plate transformer, diodes and other stuff with it.
Regards, Joerg
Once you get the transformer close, you can remove the shortfalls with a little feedback. View in a fixed-width font such as Courier.
. . 1KV . | . .----+---. ^ . | | / | . [R4] [R5] / | . | | / | . | + | / | . +--||----+ .-----+------------. -- | . | C3 | | | | |/ . | | (o | | . ||- )||( | CL === . .----||< )||( [R3] | . | ||- o)||( | | . | | | ( | | . | | | | | | . | --+--------+--+------------------' . | 1:10 | . | | . | .--[R1]--. | . | | | | . | +---||---+ | comparator . | | C2 | | . | | /| | C1 | |\\ . | /| | /-|-+--||----+------|+\\ . | /+|--+---< | | | >---. . '-< | \\+|-. | .-|-/ | . \\-|--. \\| | [R2] | |/ | . \\| | | | | | . | --- --- THRESH | . 0+ - ^ - | . | | | . | | | . | | terminate ramp | . -Vprog ----
Tube G33ks to the rescue ;)
Tim
-- Deep Fryer: a very philosophical monk. Website:
Oh yeah- for sure- check Eimac. Some decades ago I used one to generate a 1A current pulse into a 20KV load- the tube plate dropped to 1.5KV at this current, gird control voltage in the 350V range. It was a $600 tube.
Maybe it's not so much what you turn on but what you turn off. Here's a way to get around an unattainable turn-on characteristic, bit it throws more farads into C3 requirement. View in a fixed-width font such as Courier.
. . 1KV . | . .----+---. ^ . | | / | . [R4] [R5] / | . | | / | . | + | / | . +--||----+ .----+-------+------------. -- | . | C3 | | | | | |/ . | | (o --- | | . ||- )||( | | | CL === . .----||< )||( | | [R3] | . | ||- o)||( --- | | . | | | ( | TOE | | . | | | | | | | . | --+--------+--+----+--------------------' . | 1:10 | . | .------' . | .--[R1]--. | . | | | | . | +---||---+ | comparator . | | C2 | | . | | /| | C1 | |\\ . | /| | /-|-+--||----+------|+\\ . | /+|--+---< | | | >---. . '-< | \\+|-. | .-|-/ | . \\-|--. \\| | [R2] | |/ | . \\| | | | | | . | --- --- THRESH | . 0+ - ^ - | . | | | . | | | . | | terminate ramp | . -Vprog ----
In article , Winfield Hill wrote: [....]
I've never done this at 10KV but this is what I think he means to do:
============= =============== =============== Center ============================================================= ============= =============== =============== A B A B A B
You get a 3:1 turns ratio if you put this on a core and hook the "A"s together and the "B"s together.
I found 715B and 715C datasheets. That's an impressive tube!
Yes, but with 10 sections and 10kV, it's a sure recipe for coax- breakdown trouble, especially with the high voltage gradients at the ends of each section for the sections near the 10kV end. It should provide low leakage inductance, likely better than I need.
Just for visualization, assume one had ten inches of coax in the winding and running left to right. Cut or part the shield every inch, giving 11 lengths of shield; the left ends connected together and the right ends connected together - making the primary. The inner conductor is the secondary and one then could have 1:11 turn ratio. Max voltage difference would be from low end of primary to "far" end of secondary, so the coax should be rated for that value.
Yup!
- YD.
Then you may as well put the floating drivers in series and dump the transformer.
Actually, I think a 10:1 or 12:1 transmission-line transformer, made from RG-58 maybe, would work fine.
John
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