[Amps] FL-2100B Fixed

[Alek Petkovic]

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 
amp.

73 All,
Alek. VK6APK



http://www.qrz.com/vk6apk