In a message dated 9/17/2006 11:24:51 P.M. Eastern Standard Time,
bmaser@tampabay.rr.com writes:
Can anyone tell me what good is it to have one of those cone heaters in
series with the primary of the plate transformer? When the cone heater is
in the circuit, the secondary voltage is 2800VDC and when it is shorted out,
it is 3000VDC. Hardly seems worth the effort. The cold resistance of the
cone is ±30 ohms.
Bob W6TR
Bob, the initial start up voltage drop across the resistor is enough to
soft start the power supply so it does not BANG and cause undue stress on the
PS
components. Though you do not see what it actually does voltage wise, it is
in fact softening the start up as it is intended. Usually a resistor is
used in the order of 10-25 ohms, this amp opted for the cone resistance which
does the job well and will handle a lot of heat. I guess if you looked at the
ramp up of the HV on a scope you would see a big difference between using the
cone and not. You just can't see it well enough on the meter. Lou
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