Speaking of SMOKE............!!, please read below:
============================================================
In a message dated 3/22/01 7:41:56 PM Eastern Standard Time,
na9d@mindspring.com writes:
>
> Exactly!
>
> I would bet that the majority of cases of smoke and other 10 meter problems
> with SB-200s and SB-220s are from the resistor values changing due to
> heating by circulating currents.
> Therefore, a significant amount of RF circulating current flows through the
> tube and hence the LR suppressor network.
> Sure, oscillations and smoke can and do occur, but it's due to the fact
that
> the resistance in the LR network has changed from what it should be and
that
> is what changes the gain and phase margins in the circuit.
>
> 73,
>
> Jon
> NA9D
>
> on 3/22/01 10:51 AM, Phil Clements at philk5pc@tyler.net wrote:
>
> >
> >> Therefore, it's worthwhile to make sure the resistors are in good
shape,
> and replace them if needed. Measures recommends metal-oxide resistors
which
> deal with the heat much more gracefully.
> >>
> >> 73,
> >> Vic, K2VCO
> >> Fresno CA
> >
> > Sound advice! I recently measured the resistors on a SB-200 I had in for
> > repair,
> > and they had increases to nearly 60 ohms from 47 ohms over the years.
> There
> > were no signs of heating or abuse. It is a pain, but you have to remove
> one of
> > the leads of the resistor to check it.
> -------------------------------------
> Jon Ogden
> NA9D (ex: KE9NA)
>
> http://www.qsl.net/ke9na
>
> "A life lived in fear is a life half lived."
> ==========================================================
My guess is that Thomas Edison Ogden isn't aware that "CIRCULATING CURRENT'"
does NOT flow through the tube and is NOT present on the anode contrary to
what is stated in his post above. Since it is not present on the anode of
the tube, the parasitic suppressor does not see it either.
Metal Oxide resistors, as recommended by Rich, provide a high degree of
protection in the parasitic suppressor circuit. I use his metal oxide
resistors and have seen them glow red hot and survive......a feat of which
carbon resistors are not capable.
The smoke he speaks of must come from another source.
73 de
Dave, WT8R
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