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[Amps] SB220 step start blows fuses

Subject: [Amps] SB220 step start blows fuses
From: Warren Volz <>
Date: Sun, 25 Jun 2017 23:54:00 -0600
List-post: <>

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 

Any advice would be very much appreciated!


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