[Amps] Step-start and 3-500Z filament life

[Gary Schafer]

It is my understanding that the SB220 doesn't need step start for the
filaments as the transformer has enough internal resistance/inductance to
limit the inrush to a safe value for the tubes.

73
Gary K4FMX

> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]
> On Behalf Of Bill W5WVO
> Sent: Saturday, December 05, 2009 10:42 PM
> To: amps at contesting.com
> Subject: [Amps] Step-start and 3-500Z filament life
> 
> 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). How much difference does this really make in
> the life of the tubes? I would like to stop worrying about the
> tubes degrading due to filament deterioration. The tubes are brand
> new RF Parts 3-500ZGs, and I would like them to last another 20
> years or so while enduring being turned off and on once or twice a
> day. Will the step-start process ensure that kind of longevity?
> Leaving the amp running 24x7 isn't an option due to fan noise and
> power consumption.
> 
> Bill W5WVO
> 
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