>
>
>>
>> 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,
oil the bearings, and the solder does not melt.
>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.
The transformer is adequate for SSB voice service. The cooling is more
than sufficient Provided that the motor bearings are oiled regularly.
>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 .
The (5000v) bandswitch is normally protected from parasitic arcing by the
orig. c. 3900v Tune-C. Change the Tune-C to a higher breakdown voltage
unit and the open contacts of the bandswitch are more susceptable to
arcing.
>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
end
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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