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Re: [Amps] SB220 step start blows fuses

Subject: Re: [Amps] SB220 step start blows fuses
From: gudguyham--- via Amps <>
Date: Thu, 6 Jul 2017 05:12:38 -0400
List-post: <>
If you have the HV transformer disconnected as you said you added a Molex 
disconnect, and if you have the amp set for 240 instead of 120v, the fan should 
not turn with the transformer disconnected, unless you just disconnected the 
secondary from the rectifier.  In this case it might indicate a miss wiring.
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-----Original Message-----
From: Warren Volz <>
To: amps <>
Sent: Thu, Jul 6, 2017 03:11 AM
Subject: Re: [Amps] SB220 step start blows fuses

Thank you for the flood of good suggestions. I'm getting closer.

Without tubes and with the HV transformer unplugged, the fan and meter lights 
work. In addition, the step-start fuses don’t blow!

That leads me to suspect the tubes + HV supply. I checked the windings on the 
HV transformer to look for shorts:

BLK-YEL = .7 Ohm
BLKGRN - BLU = .8 Ohm
BLU - BLKRED = 0 Ohm

Do any of those look off?

Also, would these steps (or something similar) make sense?

1) Re-enable HV supply, power on, if fuses are ok power off and go to step 2
2) Once HV dissipates, add tube 1, if fuses are ok, power off and go to step 3
3) Assume tube 2 is shorted, else tube 1 is bad

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