Yaesu FT-901DM Maintenance Service Manual page 87

SERVICING
and TC2sos for maximum PO indication on
the meter. On receive, tune in the MARKER
signal, and adjust TC230s for maximum S-
meter deflection.
(12) Set the BAND switch to 20, set the VFO for
a frequency of 14.000 MHz, and set the PRE-
SELECT control to 7.2 on its scale. Dip the
PLATE control for minimum IC indication
while tuning. Set the VOX GAIN control to
MOX, and adjust TC2603 for maximum PO
indication on the meter. On receive, tune in
the MARKER signal, and adjust TC2403 for
maximum S-meter deflection.
(13) Set the BAND switch to 80, tune the main
dial for a reading of 4.000 MHz, and set the
PRESELECT control to 6 on its scale. Dip
the PLATE control for minimum IC indi-
cation while tuning. Set the VOX GAIN
control to MOX, and adjust Lo and T2s01
for maximum PO indication on the meter.
On receive, tune in the MARKER signal, and
adjust T2401 for maximum S-meter deflection.
(14) Set the main tuning dial for a reading of
3.500 MHz, and set the PRESELECT control
to 2 on its scale. Dip the PLATE control for
minimum IC indication while tuning. Set the
VOX GAIN control to MOX, and adjust
TC2z602 and TC2so2 for maximum PO indi-
cation on the meter. On receive, tune in the
MARKER signal, and adjust TC2402 for maxi-
mum S-meter deflection.
(15) Because of possible interaction of adjust-
ments, please repeat steps (13) and (14).
Set the BAND switch to 40, tune the main
dial for a reading of 7.200 MHz, and set the
PRESELECT control to 6.5 on its scale. Dip
the PLATE control for a minimum IC reading
while tuning. Set the VOX GAIN control to
MOX, and adjust TC2z603 and TC2s503
maximum PO indication on the meter. On
receive, tune in the MARKER signal, and
adjust TC2403 for maximum S-meter deflec-
tion.
(16)
for
3-32
ADVICE ON TROUBLESHOOTING
THE DRIVER/FINAL STAGES
Three tubes are used in the FT-901DM: a 12BY7A
and two 6146B's, run in parallel in the final.
Because not all service personnel are as familiar
with tubes as they are with semiconductors, we
would begin by cautioning you that tubes are
voltage devices. To produce power in useful
amounts, they require voltages well in excess of
that needed for solid state devices. Take care, lest
you quickly develop "'serviceman's elbow," a
malady well known to old timers. It occurs when
your arm jerks back from the +800 volts right into
some immovable object. Accompanied by a few
colorful phrases, it is not an experience one
knowingly encourages, though it is seldom fatal.
If you should come into contact with the high
voltage, it is best to take a break from servicing.
Alert your colleagues to what happened, and seek
medical attention should any signs of shock
(trauma) develop. Trauma following contact with
high voltage is sometimes more dangerous than the
high voltage itself. IT CAN BE FATAL!
TCse0s
TCrsoe TC.
TCasos
TC
TCaso2
TCasox