[Amps] Yaesu FL-2100B failure

[Kevin Normoyle]

My FL-2100B isn't working right.
I've probed the list and gotten some good hints, but
thought I could mine for collective wisdom also.

I bought this amp used about 2 yrs ago. So it had
been fine for a while

Symptoms:
1) 80m, 40m, 20m, 15m tune up right and I get full output.

10m: very high plate current. Can't tune it up.

2) But here's the odd thing:
The amp "works" even in Stby. I get rf out (measured thru another rf 
meter)....
i.e. the Stby/Oper switch isn't doing what it should.

That's when I realized the output relay wasn't clicking..it must be 
stuck on,
because I'm getting rf out.

It's not the Stby/Oper switch that's bad...I correctly don't get any 
voltage on
keying (RLY) connections till I'm in Oper..and the red light isn't on 
until Oper...
that makes sense from the schematics.

..so that got me wondering how both the grid bias and the output relay must
be on, independent of the Stby/Oper switch.

Looks like they share parts of the same circuit.

Been reading all the stuff about grid bias cutoff being insufficient ( I 
think I have
811A tubes) and oscillation in 10m and wondering if that might apply. 
The amp
had been working for a while...plus it wouldn't explain why the output relay
would be stuck on?

I'm wondering if I have some burnt out resistors in the grid/relay circuit.

Anyone seen stuff like this? I'm thinking I can see how a burnt out resistor
may cause the grid bias to not cutoff and the output relay to be on, but 
not sure
why that would kill 10m, unless something else is messed up.

I see people complain a lot about arcing in the bad switch. I suppose I 
could
check that also.

Thanks,
Kevin
KE6RAD