Mike,
If I understand correctly, to do what you are suggesting, I would need
for the primary to be center tapped. This transformer is not center
tapped, but does have some taps for setting the primary voltage - 205,
220, 230, 240, 250. It is an old Gates plate transformer from a
broadcast transmitter. I might try Chucks idea for using a bucking
transformer. I think I have one that would work.
Another possibility is to use the 250 volt tap on the primary and wire
the secondary in a choke input configuration. I have the choke that was
used with this plate transformer. That might be enough to get the
voltage down where I need it. If not, then I could add a bucking
transformer. 4000 volts is my absolute max.
I'm using a GS-35B which is marginal at that voltage, but I've seen guys
running them that high with no problems. If you fry a tube, they are
relatively inexpensive. A friend who recently became a SK gave me four
of them, so I should be good to go for a while.
Thanks for the tips, guys.
Larry W4LK
On 02/02/2015 03:58 PM, Mike Waters wrote:
It sounds like a 115 volt-only Variac, so you can use it between the
neutral and one 240V leg. You just connect your 240V plate transformer
primary between the Variac wiper and the remaining leg of the 240V circuit.
That's the way my filaments are wired in my dual 833C amplifier. You get
finer control of the voltage, but you can only adjust the primary between
120 and 240 rather than 0 to 240.
73, Mike
www.w0btu.com
On Mon, Feb 2, 2015 at 2:41 PM, Larry <LKIRKLAND@sc.rr.com> wrote:
I am building an amp and have started gathering parts for it. My plate
transformer secondary is rated at 3500 VAC. Thats a little much for what I
need. I need to end up with about 3500 VDC for the amp. I found an old
General Radio Variac type V10 good for 10 amps, but I'm not clear if it can
be used on 220 VAC. The wiring diagram on it says "volts shown for input
115 volts 50-60 cps."
My question is Can I put 220 volts across the coil without smoking it?
I'm thinking that it would work.
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