Yes, there were some other forces at work, I seems that there was a
parasitic oscilation as one of the 1mH chokes smoked. I have installed the
parasitic kit from Rich and replaced the Zener with seven diodes. I would
like to get a .82 ohm resister put back in but may test the amp with a
jumper. They are mighty scarce around here as are other values. The only
thing we have in this area are Radioshacks :-(
Darryl - K5WAS
> It seems quite unlikely that 120 watts would blow the .82 ohm shunt. Oter
> forces were at work (Parasitics likely). I often looked at the grid
current
> but never actually used the reading for anything. Its the readings on the
> plate side that make the difference. The Grid current is what it is. Maybe
> it could be useful in the one time tuning of the input circuit but even
then
> one can look at the output. But when that .82 goes, it can take out the
> meter. Short is a good idea, and remove the short if you ever need to
> monitor grid current, assuming you put another .82 in there. Mine is
blown,
> meter survived. Replacing it with wire! --Mike, WV2ZOW
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]On
> Behalf Of R.Measures
> Sent: Tuesday, December 07, 2004 11:39 AM
> To: kwasny
> Cc: amps@contesting.com
> Subject: Re: RE : [Amps] .82 ohm
>
>
>
> On Dec 7, 2004, at 7:24 AM, kwasny wrote:
>
> >
> > ----- Original Message -----
> > From: "R.Measures" <r@somis.org>
> > To: "hermans" <on4kj@skynet.be>
> > Cc: <amps@contesting.com>; "'kwasny'" <kwasny@netzero.net>
> > Sent: Monday, December 06, 2004 3:30 PM
> > Subject: Re: RE : [Amps] .82 ohm
> >
> > How would one determine if the grid current is being exceded?
>
> -- There is no max. grid-I rating on 3-500Zs or 3-400Zs. The max.
> grid dissipation for a pair is 40w, however, provided that it isn't
> being driven beyond the max anode-I rating of 0.8A, if a g-g amplifier
> is tuned for max P-out, grid dissipation will always be reasonable.
> The reason for this is that diverting more electron flow to the grid
> requires detuning so that less than optimal power out results. Thus,
> when P-out is max, one can relax.
> - The type of amplifier that requires a grid-I meter is: Class AB1
> grid-driven, not Class AB2 cathode-driven.
>
> > I have no
> > doubt that is was caused the problem with my SB-220 in the first
> > place. I
> > inadvertently drove it at full output from my exciter (110 to 120
> > watts).
> > That is when the trouble started.
>
> Whenever I tune my SB-220 or TL-922,, I fully drive it to 0.8A because
> I know that if I drive it to less anode current, RL will decrease and
> I will have a mistune when I drive it to full PEP.
> >
>
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>
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