Negative.
There are 2 transformers in a SB-220. 1 filament and 1 for HV.
The step start mod (from harbaugh) is wired in series with both transformer
primaries.
So step start helps both HV and filament.
73
Jim W7RY
----- Original Message -----
From: <vk3pa@vk3pa.com>
To: <amps@contesting.com>
Sent: Saturday, December 05, 2009 8:38 PM
Subject: Re: [Amps] Step-start and 3-500Z filament life
> Quoting Ron Youvan <ka4inm@tampabay.rr.com>:
> yes its on the pri input to the t/former ..heater /ht on same t/former
> a slow fil input will save the tube life as we all, know when a ligh
> globe is s/w on or off is when it fails..
>
>
>>> I understand why turning a tube's filaments off and on repeatedly
>>> shortens the tube's useful life. However, I'm not clear about the
>>> effects of doing this when a step-start circuit is included (as in
>>> the Harbaugh step-start kit, which I have installed in my
>>> 6m-converted SB-220).
>>
>> I think of "step-start" as applying to the plate supply, to
>> minimize the initial capacitor
>> charging current and preventing a hV over shoot, and inrush limiting
>> to be applied to initial
>> filament heating, does the Harbaugh step-start kit effect both?
>> --
>> Ron KA4INM - The only real problem is death is so final.
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>>
>
>
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