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
-----Original Message-----
From: Kim Elmore
Sent: Tuesday, December 26, 2017 9:58 PM
To: Warren Volz
Cc: amps@contesting.com
Subject: Re: [Amps] Soft Start
A related question. Once long ago I read that power cycles are very hard on
filaments. Is that also the case with soft starts, or does the soft start
reduce the thermal shock issues?
Kim N5OP
"People that make music together cannot be enemies, at least as long as the
music lasts." -- Paul Hindemith
On Dec 26, 2017, at 21:08, Warren Volz <warren@warrenvolz.com> wrote:
I’d recommend a step start with fuses. I have w7ry’s board in my sb220 and
the fuses saved me from a bad tube once already.
-Warren
On Dec 26, 2017, at 8:59 PM, Jim W7RY <jimw7ry@gmail.com> wrote:
I recommend 10 Ohms. I use 2 resistors and 2 relays. There are fuses in
series with the resistors to protect them.
Why would a cap blowing up cause an issue with a step start circuit?
Again, I use 2 resistors and 2 relays on a small circuit board.
See:
https://www.ebay.com/itm/282765541853?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649
73
Jim W7RY
-----Original Message----- From: Arnie Pfingst
Sent: Tuesday, December 26, 2017 8:31 PM
To: amps@contesting.com
Subject: [Amps] Soft Start
Once upon a time, i had a capacitor explode upon start up. I've heard
stories for and against adding a soft start circuit to my
amplifiers.(Some say 20 ohm resistors, and others say 30 or 40 ohm.) That
and the price of replacement tubes. In my case i have two TL 922a amps
using 3-500z tubes.
Both set up on 240vac. What do you all have to say here. Thanks
Arnie
Sent via the Samsung Galaxy S8 Active, an AT&T 4G LTE smartphone
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