On Mon, 7 Jul 97 11:06:57 -0700 Rich Measures <measures@vc.net> writes:
>>IMO, adding Step-Start to the SB-220 is a complete waste of time and
>>money. The filament xfmr was designed to limit inrush current. The
>plate
>>xfmr is also current limited.
>...snip...
>- The HV transformer is required to produce repetitive, high peak
>currents to satisfy the considerable demand of the C-filter. If the
>HV
>transformer were designed to limit current--like the 220's filament
>transformer--the HV regulation would be unacceptable.
I did not say that the xfmr was designed to limit current, I said it was
current limited....there is a big difference between the two.
>- When a stock SB-220 is consistently started up on the SSB HV tap,
>the
>inrush current is such that the life expectancy of the on/off switch
>is
>reduced.
Possibly, but I suspect the majority of On-OFF switch failures are purely
worn out. Starting any amp in the low power position (if available) is a
good idea anyway. Replacing an old switch is certainly preferred over
adding more failure prone parts to the circuit.
BTW, I have a large stock of old National NCL-2000 ON-OFF switches, they
fit the SB-220 exactly and are a grade above the cost conscious Heathkit.
73...Carl KM1H
BTW, whoever was looking for Harbach, they advertise in the Ham-Ads of
QST every month. Also at www.harbach.com
Two solutions are: Use the switch manufacturer's 40a
>inrush-I
>version (Arrow p/n 2800HM11 C ) of the switch, or install a step-start
>
>relay.
>Rich---
>
>R. L. Measures, 805-386-3734, AG6K
>
>
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