With such a marginal variac the DC dynamic regulation is going to be pretty
poor.
When all else fails consider a choke input at least until you can get a
proper transformer, you will wind
up with about 3000-3100VDC with stiff regulation when followed by a decent
output cap and a bit of mandatory bleeder current.
Or a big honkin' 30A 240V Variac which is what I use after a $45 hamfest
find, it was actually a pair for $90!
That feeds a custom transformer with 4 output taps and a WW2 BC-375 switch
to select them. I can go from 0-4200V DC @ 2A CCS
and feed my 144 and 222 mHz amps plus some ancient AM amps as well as run
all sorts of IMD tests on others.
Carl
KM1H
--------------------------------------------------
From: "Mike Waters" <mikewate@gmail.com>
Sent: Monday, February 02, 2015 7:35 PM
To: <amps@contesting.com>
Subject: Re: [Amps] Variac Question
10 amps is pretty marginal, yes. But he might just get away with it,
provided he doesn't use a continuous-duty mode like RTTY. That 10 amp
rating is for CCS, not ICAS.
My HV Variac (a Staco type 1250) in my legal-limit amp is only rated for
(IIRC) 12.5 amps, and it doesn't overheat.
73, Mike
www.w0btu.com
On Mon, Feb 2, 2015 at 3:38 PM, Paul Hewitt <wd7s@earthlink.net> wrote:
This works if you have a neutral in the psu but you will be limited to
ten
amps for the plate transformer primary, pretty thin for most legal limit
amps.
73, Paul
Paul Hewitt
WD7S Productions
QRO Homebrew components
http://home.earthlink.net/~wd7s/contents.htm
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Mike Waters
Sent: Monday, February 02, 2015 12:58 PM
To: amps@contesting.com
Subject: Re: [Amps] Variac Question
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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