Yaesu FT-902DM, Instruction Manual

Page: 50 / 55

1 5 . POWER OUTPUT METER ADJUSTMENT
VR7 , l ocated on the transceiver rear panel adj a­
cent to the RCV ANT jack, provides adjustmen t
for the relative power output indication on the
front panel me ter.
With the transceiver tuned at full power into a
5 0 Ohm dummy load , VR7 should be adjusted
to indicate 1 / 2 to 2/3 ful l scale meter deflection ,
with the METER switch in the PO position .
I t should b e noted that the PO meter indicates
relative power output, and it is not the basis for
determining actual power output .
VR7 has been preset at the factory to read l / 2
to 2 / 3 full scale i n t o a 5 0 Ohm dummy l oad . The
operator should not indiscriminately adjust V R 7
while using a n unknown load or antenna of p os­
sibly high VSW R .
P O M e t e r Adj u s t ( VR 1 ) Accessory P l ug
1 6.
FINAL AMP LIFIER NEUTRALIZATION
When replacing the final amplifier tubes, it may
b e necessary to reset the bias to give the correct
idling current, and to check neutralization. Using
the procedure outlined below will guaran tee
maximum output and long tube life.
CAUTION
HIGH VOLT AGE S ARE PRESENT ON THE
UNDERSIDE OF THE CHASSIS AND INSIDE
THE FINAL AMPLI F I E R COMPARTMENT. U S E
G REAT C A R E W H I L E MAKING ADJUSTMENTS
I N AREAS OF EXPOSED WI RING .
( I )
Connect a dummy load to the antenna re­
ceptacle , and se t the METER switch to IC.
( 2 ) Locate TC0 1 , the neutralization variable
capacitor shaft , on the inside wall of the
final amplifier comp artment.
(3) Check the final amplifier idling current as
described in part 14 of this section of the
manual (BIAS ADJUSTMENT).
(4) Tune up the transceiver at . 29 MHz, using
either the 1 OB or 1 OC b and, and adjust the
carrier level so that it is 1 5 0 mA in the
TUNE condition.
( 5 ) Rotate the PLATE tuning control and ob­
serve the poin t of minimum current ("dip " ) .
If the d ip is n o t prominent, reduce the
LOADING control slightly to get a be tter
dip. As the PLATE control is rotated the
meter should rise equally and smoo thly on
either side of the dip.
(6) Determine which sid e of the dip rises ab­
ruptly. Set the P LATE c ontrol slightly t o
this side of the dip, keep the meter reading
below 1 00 mA.
( 7 ) Using a nonme tallic tuning wand, ro tate the
neutralization capacitor shaft very sligh tly
in the direction which reduces the current
on the meter. R epeat steps 6 and 7 until
the meter indicates a smooth and equal
rise on either side o f the dip.
NOT E : The final amplifier c ompartment cover
must be in place to supply the RF
shielding required during the neu trali­
za tion procedure .
- 4 8 -
V C 1
V C 2
T C 1
Final Ampli f i e r Compa r t ment
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