> Tom I usely have an HT transformer and then a seperate transformer for
> grid,screen and control (aux) voltages.I have started to get transformers
> custom wound locally as I have found it quite cost effective.I still need
> to get big HT caps from the US.How much will an 8kV 40 mfd HT cap cost me
> surplus these days?(Winter project).
22uF 4 kV caps are about $30 surplus here.
You don't need a separate transformer for the system I described, if
you have a dump relay on the primary that activates with a fault. A
relay will be fast enough.
The advantages are it fails safe and limits screen dissipation
instantly...without relying on any other devices.
Screen dissipation is limited by the ESR of the source. As long as
the source voltage for the shunt regulator is twice the operating
screen voltage or higher, you can never overdissipate the screen.
I use such systems all the time in big tubes, like 4CX10000's and
larger, but it also works great in small PA's like 4CX250's.
73, Tom W8JI
w8ji@contesting.com
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