[Top] [All Lists]

[Amps] FL-2100B Fixed

Subject: [Amps] FL-2100B Fixed
From: Alek Petkovic <>
Date: Wed, 07 Dec 2005 17:05:37 +0800
List-post: <>
Thanks to all who offered their assistance regarding the arcing 2100B. The 
amp has been stabilised.

Dave, W8NF and Rich, AG6K were instrumental in curing the problem.

I checked the 33 Ohm grid resistors and they were a bit higher than spec. 
They were not the original items. I changed them for some 30 Ohm units and 
added around 1000pF to the existing 200pF grid capacitors.

As well, I made up some Nichrome suppressors from a spare kit I had lying 
around. With these and the grid mods, the amp has become unconditionally 
stable when keyed up with open circuit input and output terminals.

Before, I added the nichrome suppressors, I installed a couple of good 
suppressors from a previously modded 2100Z. With these installed, with the 
grid mods, the amp still produced a purple arc between the plates of the 
loading cap.

I carried out tests for arcing after each step described above. It wasn't 
until all  the mods were done that the amp started to behave.

I hasten to point out that the amplifier seemed totally ok before any mods 
were done with a radio on the input and a load on the output. It was only 
by chance that I had the amp on the bench with nothing connected to it.

Other 2100B owners might care to experiment along the same lines with their 

73 All,
Alek. VK6APK 

Amps mailing list

<Prev in Thread] Current Thread [Next in Thread>