>
> That's because it has headroom in the components. Technically,
> the transformer is a tad small and the cooling is a bit marginal for
> 1000 watts out.
>
> The power limit was 1 KW input, and 2 KW PEP input on
> SSB...and that's what the 220 was designed to do plus a safety
> margin.
>
> That's why some people have trouble with the tube pins
> unsoldering, and plate transformers failing. The manual doesn't say
> 2KW output, it says 1000 watts input on CW and 2 KW PEP on
> SSB. If you ran it like that, it would last almost forever.
>
>
>
> 73, Tom W8JI
> w8ji@contesting.com
Original SB220 transformer is rather weak, also at 1000W DC, and cooling is
also insufficient.
I was asked friends to modifiy SB220 (5 units) in the early 80's with an
external HV supply and a full wave rectifier (no voltage doubler) to have
3500V DC on TX (bias had to be reduced, of course).
I can report that the output power increased noticeably from the original
unit, so much that the original fan had also to be replaced with a more
consistent one likewise the plate capacitor was prone to arc and had to be
replaced with the larger spaced type (SB221) or a vacuum .
Those 5 SB220 are still in service after 20 years, whose is the sign that,
transformer and cooling apart, SB220 is instead useable (with some care) at
1300-1500 W, or even more.
73,
Mauri I4JMY
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