[Amps] SB220 step start blows fuses

warren at warrenvolz.com warren at warrenvolz.com
Thu Jul 6 12:55:41 EDT 2017

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, gudguyham at aol.com 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 <warren at warrenvolz.com>
> To: amps <amps at contesting.com>
> 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 _______________________________________________ Amps mailing list Amps at contesting.com http://lists.contesting.com/mailman/listinfo/amps

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