[Amps] [AMPS] Re: FL-2100B Failure

[Joe Subich, K4IK]

Kevin writes:

> with respect to the burning on the plate choke: yup it's only 
> in certain areas.  So the comments about vhf parasitics are 
> probably right on, if that's a key indicator.
> 
> The 22 ohm suppressor R's physically looked okay, but I'll 
> be sure to measure them.

These two observations point not to parasitics but an attempt 
to operate the amplifier on a band for which it was not designed 
perhaps 17, 12 or 11 meters.  Burning in certain areas of the 
plate choke indicates high voltage at that point, probably due 
to a resonance.  That often happens to older amplifiers not 
designed with "WARC" band operation in mind.  

Some very good examples are the MLA-2500 which had a resonance 
near the 17 meter band and the Alpha 76 series of amplifiers 
that intentionally had a choke resonance around 25 MHz which, 
while it prevented operation on 11 meters, happens to prevent 
the amplifier from being used on 12 meters. 

73, 

   ... Joe, K4IK