Hi:
I not have FT-50, but I have FT-200 with 6JS6 (x2) tubes in
amplifier outpout.- The plate voltage can be around 700 to 800 volt. , not
350.- It is a cause yoir problem off low power.- The idle plate current can
be 50 or 60 ma.
I suspect that to his problem this in power supply.-

Regards
Heriberto
LU6DBU

escribió en el mensaje
oups.com...
I think I would be looking for a manual for it . The people that
designed it probably know more about it than anyone else.. HS
Andrea Baldoni wrote:
Hello!
I'm trying to repair a Sommerkamp(Yaesu) FL-50B. It does power up and
transmit
but the output power is just 13W. I tried to replace final 6JS6C without
any
adwantage, also replace the driver tube with same result.

The B+ is 350V, dropping to 325V while transmitting... Already tried to
exchange the plate voltage filter condenser, but apart slightly minor
ripple,
no result in power output increase.

The transmitter is fully tuned, by me who may be not the best man for
that,
but hovever, I have a good oscilloscope and anyway, the power output
before
tuning was a (little little) less.

The antenna relay is ok. By measuring with oscilloscope the grid of the
6JS6C, I notice increasing in signal amplitude while rotating full scale
"carrier" control from 0 to 8. After 8, signal no more increase and
there
is a little derive in 5.12.. Mhz carrier frequency. I think this is
normal
for this kind of transmitter. The strange fact instead is that despite
driver signal is increasing, output power no further increase after
carrier
control position 4.

I have regulated bias to 60mA, I suppose it's good for 6JS6C, I have not
the
manual of the transmitter so I don't know exactly. Anyway, this has no
strong influence over power output. While at full power, I never see IC
more than 125mA, that's half the scale of the instrument. In PO measure,
it signs slightly more than .2

Well, no more. Someone who has more experience than me, please give me
his help!

...and also, I need to know what's (in Vpp) the right output of the
carrier
quartz oscillator measured at the input of the balanced modulator.
While tuning, I forgot to record the previous amplitude... Now, if I
recall
correctly, is 2.5Vpp... More than 3.5Vpp, the oscillator become unstable
and
may not start oscillating, less than 2.5, output power further
decrease...
So I may be right, but I would like to know if there is an exact value
to
regulate on.

The power is more or less the same in every band, I use an FR-50B as
VFO,
but with a 9MHZ quartz I have, the results are unchanged. All measure
are
on a 50R dummy load with wattmeter. A Osker Block SWR/Wattmeter inserted
hovewer sign the same output and no SWR.

Ciao,
AB