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Re: [Amps] SB220 step start blows fuses

Subject: Re: [Amps] SB220 step start blows fuses
Date: Thu, 06 Jul 2017 10:55:41 -0600
List-post: <>
And I keep leaving out important details... Due to the current wiring in
my shack and a desire to test I'm running this on 120v. I know this is
not the best idea long term, but it does allow me to test everything.
One last detail I've left out is that I have the W7RY step start and QSK
mods installed. I checked the transmit/receive functionality of the QSK
board last night and it's working very well. The vacuum relays are
amazingly quiet. 

Related, does anyone have a suggestion on how best to check and adjust
the bias from the QSK board? 


On 07/06/2017 3:12 am, wrote:

> 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.
> Sent from AOL Mobile Mail
> -----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 BLK-BLKYEL = .6 Ohm BLKYEL-YEL = 0 Ohm BLKGRN - BLU 
> = .8 Ohm BLKGRN - BLKRED = .6 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 -Warren 
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