Yes, you're right about doubling the current. I was definitely exaggerating!
Trying to
talk myself into it. You are right about shipping something that heavy by air!
It would
probably cost less to buy a NEW one.
On 3/19/2010 5:01 PM, Manfred Mornhinweg wrote:
> Vic,
>
>> So the primary is good for 313 VA continuous.
>
> Yes - but the secondary isn't!
>
>> I was doubling that to allow for the duty cycle. I agree that this is
>> skating on the edge (standard ham practice, right?)
>
> Actually it's quite a bit over the edge! You are forgetting that
> doubling the current QUADRUPLES the power loss in the windings! That's
> OK only if you reduce the duty cycle to 25% maximum, and also make the
> cycles short enough to keep the wire from overheating during one cycle.
>
> I would say, pushing a transformer to twice its continuous current
> rating is perfectly OK for the PEP level of a SSB amplifier, as long as
> not too much voice processing is used. But definitely not OK for CW!
>
>> However... the 813's deserve better. So I think I am going to look
>> around for a transformer that I can get 2400 - 2800 V at 350 - 400 mA
>> from.
>
> That's MUCH better!
>
> About ten years ago I wound one like that. It also has the 10V filament
> winding, and windings for screen an bias supplies. And I never used it,
> because while I was building the amp, I got the chance to buy the
> National Radio amp for almost no cost, and that made me shelf the 813
> amp project.
>
> But shipping that beast to you would certainly be more expensive than
> getting one locally!
>
> Manfred.
--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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