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Re: [Amps] SB220 step start blows fuses

To: <>
Subject: Re: [Amps] SB220 step start blows fuses
From: Catherine James <>
Reply-to: Catherine James <>
Date: Mon, 26 Jun 2017 12:28:59 +0000 (UTC)
List-post: <>
Any time the fan doesn't start immediately after power-up, shut down your 
SB-220 **immediately**.  You may have a short, and if the breakers/fuses don't 
blow, you will smoke the power supply very quickly.


On Mon, 6/26/17, Warren Volz <> wrote:

 Subject: [Amps] SB220 step start blows fuses
 Date: Monday, June 26, 2017, 1:54 AM
 I’ve been restoring a SB220 and
 finally got to the testing stage this weekend. When I turned
 it on, the HV went up to ~1kV and then started to drop.
 Successive cycles of the power switch did nothing. Oddly,
 the meter lights and fan never started running. I looked at
 the bottom of the amp tonight and the 3A fuses I added to
 the W7RY step start board blew. What areas should I look at
 now to determine what is going wrong? I have both tubes in,
 and I believe I previously checked them for filament shorts.
 I’m worried the HV supply has an issue.
 Any advice would be very much
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