[Amps] SB220 step start blows fuses

Joe nss at mwt.net
Sun Jul 23 18:47:42 EDT 2017

On 7/23/2017 4:23 PM, Geert Jan de Groot wrote:
> Sorry for raking up an older topic; I don't always have time
> to keep up with mail.
> If the thing is wired for 220V, and instead of powering with 220V
> one powers with 5V AC in the primary, then the secondary circuit
> works except that instead of messing with 2000V, one now works with
> 50V on the HV circuit. That is plenty to test diodes, measure caps etc,
> and it's a while lot less nerving.
> One has to realize that the filaments of the tubes will represent
> a dead short (5V, 15A when in operation; cold resistance is less)
> but I found this to be a lot less nerve wrecking and a lot safer
> than trying to put line voltage on, with or without lamp,
> with or without variac
So what is happening with the tube power supply? When running with this 
minuscule voltage?


> 73, Geert Jan PE1HZG
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