>> From: Rich Measures <measures@vc.net>
To: <amps@contesting.com>
>> Date: Sun, 7 Sep 97 17:34:55 +0000
>
>> >Except for some strange reason the very resistors that Rich
>> >calculates to be perfectly fine commonly fail!
>> >
>> - The 'Ra' resistors are intended to be anode fuses. During a serious
>> glitch, they open. Does it seem strange that a fusing element
>> occasionally opens?
>
>The resistors in your suppressors and you glitch resistors also
>change value gradually over time.
During prolonged RTTY or FM operations on 10m, the resistance of the 1.0
ohm anode fuse resistors (Ra) gradually decreases about 10%. ... I have
seen no evidence that the 10 ohm, 10w glitch resistor (Gr) - in series
with the anode supply - changes value gradually. This should come as no
surprise. Key-down, at full-throttle, the typical dissipation is 6.4w.
> Of course, when the resistor is a
>REGULAR resistor in a conventional system any change in resistance is
>due to "parasitics".... or so you claim.
I stated that a substantive increase in resistance, especially with no
outward signs of damage, is likely to be intermittent
VHF-parasitic-related. Since Rs is virtually shorted out by Ls at HF,
VHF energy is required to substantively overload Rs.
>
>I'm a little puzzled by what seems to be a contradiction.....
:-) Translation: contradiction = opportunity
>1.) We know these resistors are used in amplifiers that have all the
>"hottest" (pardon the pun) stability mods.
>
An approproiate pun, Mr. Rauch. Effective VHF suppressors that don't get
hot at 28MHz would be too good to be true.
>2.) You claim most (if not all) glitches in NON-modified amps are
>supposedly due to parasitics (even when the PA is on standby).
>
..... roughly 5% of incidents, according to reports from amplifier owners
during the past 10 years.
>3.) You claim gas related arcs can't come and go, the tube can't
>getter itself so the gas remains even after the arc.
Gettering with a cold filament? Vanishing gas? ...... Thick-sliced
bologna.
>
>4.) You say the "fuse" resistors "occasionally" fail in the
>nichrome modified amps from "giltches".
... Forrest Gump said "Shit happens".
>
>Number four must mean amplifiers with your mods still "oscillate",
>since you always say numbers 1-3 are correct.
>
Such amplifiers occasionally oscillate - however - seemingly less often.
/ "Always"?
- Some of the issues between us appear to involve failure to read what I
write. You have often asserted that I say that 'parasitics bend grids' .
. . . The first photograph in "Parasitics Revisited" [9/90 QST] shows a
bent 3-500Z filament-helix rubbing noses with a grid cage whose wires are
quite obviously straight. Does it seem very likely that I would
subsequently make the statement that 'parasitics bend grids'?
Cheers
Rich---
R. L. Measures, 805-386-3734, AG6K
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