> From: km1h@juno.com (km1h @ juno.com)
To: <amps@contesting.com>
> Date: Tue, 8 Jul 97 12:41:48 +0000
> Rich, Bill, etc
>
> The big difference is the word "designed". I dont believe that the Heath
> engineers were overly concerned about PS inrush current. It wasnt a
> marketing hype word back then.
That's correct Carl. Inrush was never a part of the concern. It
wasn't until 1970 or so that inrush became the curse of the 220,
causing arcs and pops and snaps and blowing out tubes.
In the 80's, it became fashionable to blame all the voo-doo science
claims of 70's inrush worries on parasitics. Hopefully in the 90's
and beyond we will stay with science, and put the batwings and eye of
Newt back in the footlocker.
The current limits because of the components internal ESR, which was
a natural result of the low power levels (1 kW ICAS INPUT power) and
duty cycle (less than 50%) the 220 was designed for. Same with the
filament transformer, any properly sized transformer combined
with the resistance of the filament choke, wiring, power line
ESR, and so on would limit filament inrush. There was no special
design, it was a conventional transformer.
> The very heavy bleeder string also tends to limit inrush current.
The bleeder string actually has no effect except to INCREASE
inrush if you re-cycle the amp in a short time period.
Just replace the 20 year old part that finally failed and get on
with operating.
73, Tom W8JI
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