>> I believe many old 3-500Zs are in SB-220s, which are designed to this
>> standard. No?
>
>Inrush related failures are pretty rare Pete, especially if you do not
>oversize components in the filament.
>
>Buzz WA4GPM, a former senior engineer at Salt Lake,
** During the Grate Debate, on 6 Dec, 1966, Mr Tom Rauch said:
"As we can plainly see, I did post three names of Varian engineers who
totally disagree with Richard (Reid Brandon, Buzz Miklos, and John
Button). Of the three, Miklos is the most technically inclined, since he
actually designs tubes and oversaw the entire staff in R and D at Varian."
- However, Varian's personel department's spokesperson said Miklos was
not the R and D manager. He was an "Engineer B" -- which she explained
is the lowest grade of engineer in Eimac-Varian's Salt Lake City
facility. As I understand it, WA4GPM hands out business cards at Ham
conventions claiming to be what Mr. Rauch says.
>told me they strapped
>3-500Z's filaments to very large filament transformers and cycled them off
>and on hundreds of times with recording any failures.
>
>Damage is a time and amount problem, if there is any damage. The peak inrush
>in a SB220 isn't much over twice the rated current, so it wouldn't be a
>problem anyway.
** The cold-resistance of a 3-500Z filament is c. 1/8 of the
hot-resistance. Thus, the filament should initially draw c. 8-times the
rated 14.7A (c.117A) at start-up from a 0-ohm 5V source.
>
>If you look back, you'll find a wave of "it must have been inrush" worries
>in the 70's caused by one or two articles telling everyone how inrush was
>killing reliability in the SB220. Naturally the articles and resulting
>hysteria and series of modifications were unfounded.
>
** Indeed, Tom. No one seemed to notice that the 3-500Z has feedback-C.
- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
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