|[AMRadio] Re: Need list of good AM radios to start lookingfor.|
k4kyv at hotmail.com
Sun Nov 27 00:59:48 EST 2005
>From: "John E. Coleman (ARS WA5BXO)" <wa5bxo2005 at pctechref.com>
> The power that you run is determined by the load resistance that the
>plate circuit is working into, and the voltage... If you maintain the
>same voltage and loading position on the knobs,
>therefore reflecting the same Z to the plate and then plug in a smaller
>you will just over heat the smaller tube.
I have seen that verified when I had the filament of one of the two final
tubes go out. The plate current remained near normal, and the only thing I
noticed abnormal about the meter readings was an unusual amount of downward
modulation. Looked into the final amp compartment, and noticed one filament
dark but the plate was glowing red on the other tube, because it was taking
all the load. The downward modulation was a result of the overloaded tube
going into saturation on modulation peaks.
Turns out the dark tube wasn't bad. Took it out of the socket and cleaned
the filament pins with steel wool and it started working again.
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