[Amps] Soft Start

[Kim Elmore]

This makes a case that it isn't the rate at which  the filament 
temperature rises, but in stead the fact that it passes through a 
particular temperature at all. If it passes through ~900F, then the 
Miller-Larson effect occurs and there's nothing we can do to alter it. 
I've always treated the amp carefully and once I turn it on (it's an 
AL-1200 with a 3CX1200A7), it stays on for the duration of my activity. 
I'll keep doing that. I have a  a spare tube, but they are very 
expensive beasts!

Kim N5OP


On 12/27/2017 2:34 PM, Bryan Swadener via Amps wrote:
> FWIW, Mike WØBTU put this together, s'plaining the "Miller-Larson Effect":
> http://www.w0btu.com/miller-larson_effect.html.
>
>
> Though, in some cases (such as in the SB-220), there's little/no benefit,
> as the filament transformer limits the current. In those cases, you're
> mainly extending the life of the ON/OFF switch from yuuuge inrush current
> caused by overly large HV filter capacitance.
>
> vy 73,
> Bryan WA7PRC
>
>
> Date: Wed, 27 Dec 2017 06:25:27 -0600
> From: Jim W7RY
> Subject: Re: [Amps] Soft Start
>
> Soft start (I call it step start) does reduce filament inrush current. As
> long as it's on the filament transformer primary.
>
> Which it is in the SB200, SB220, TL922, L4B and TenTec Titan... And many
> others.
>
> 73
> Jim W7RY
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-- 

Kim Elmore, Ph.D. (Adj. Assoc. Prof., OU School of Meteorology, CCM, PP 
SEL/MEL/Glider, N5OP, 2nd Class Radiotelegraph, GROL)

/"In theory there is no difference between theory and practice. But, in 
practice, there is." //– Attributed to many people; it’s so true that it 
doesn’t matter who said it./