[Amps] FL2100B

[Punkymcd@pacbell.net]

FWIW

Recently a friend called and asked if I would take a look at a his Yaesu FL2100B 
that he was having problems with. Said no output on 80 and minimal on higher 
bands. He purchased the amp in this condition from another ham. Said he had only 
been using it on 20M. (not much output when I measured it)

He had replaced the output bandswitch wafer which had blown (undoubtedly caused 
by a parasitic) and removed a variable capacitor that had been tacked on to the 
output end of the 20M input pi network.

Found the 1000pf cathode coupling capacitor and the original output capacitor of 
the 20M input pi network had both opened (read about 45pf). Amp is working fine now.

An issue FL2100B users should take note of, probably discussed in earlier 
threads. This amp was set up to run on 220. Apparently at the time these 
amplifiers were in production line voltages were 220 but in our area, and I 
suspecet others, it is now 240+/-. (not sure when this changeover took place) 
Taps on the transormer allow for up to 234V. As you might suspect, besides the 
HV being a bit higher, so was the filament voltage at around 7.4V. Even when the 
line voltage taps were set to 234V the filament voltage only dropped to 6.8V. 
About .9 ohms in series with the filament xfmr lead would drop it ot about 6.1 
or 6.2V.

73, Don, W6OA

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