[Amps] Variac Question

[Carl]

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 at gmail.com>
Sent: Monday, February 02, 2015 7:35 PM
To: <amps at 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 at 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 at contesting.com] On Behalf Of Mike Waters
>> Sent: Monday, February 02, 2015 12:58 PM
>> To: amps at 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 at 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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>>
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