On Apr 20, 2004, at 11:29 AM, Jim Isbell wrote:
After collecting parts for most of a year I am in the serious design
stage of a 4-1000A linear. The power supply, because of its size is
to be external and connected by a cable.
In the first design I was going to bring the 6500VDC power through a
cable to the linear. But then it occurred to me that since the main
reason for the separate supply was the size...which is MOSTLY the
12KVA transformer I am using. It might be safer to just make the
transformer external and have the rectifiers and filter capacitors in
the transmitter case thus allowing the only the transmission of AC, at
a lower potential, (using a voltage doubler circuit) in the cable.
Thus, by just turning off the input power I could eliminate the
potential on the cable instantly...or almost so...while the filter
capacitors which are the biggest danger would be in the transmitter
cage and would be connected to shorting circuits controlled by the
safety switches on the lid of the transmitter.
There must be some reason this is not a good idea as I have never seen
it done.
Any comments???
Jim -- I see it as a sound idea provided there is room for the
filter capacitors in the RF unit. However, a 12kva transformer would
be more suitable for an 8171 than an 8166/4-1000A. Switching to such
would not require a larger chassis since either tube requires c. 8" x
8" of chassis space. Advantages with the 8171 are a simpler tuned
input circuit, a quieter blower, and 6x the peak emission. If you
have a 4" deep chassis, Peter Dahl makes a 7.5v, 75A filament
transformer that will fit in a 4" chassis. On E-bay, I've seen 8171s
go for c. $300.
cheerz
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Rich Measures, AG6K, 805.386.3734. www.somis.org/
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