Yaesu FT-901DM Instruction Manual page 47

1 5 . POWER OUTPUT METER ADJUSTMENT
VR7 , located on the transceiver rear panel adja­
cent to the RCV ANT j ack, provides adjustmen t
for the relative power output indication on the
fron t pan e l meter.
With the transceiver tuned at full power into a
5 0 Ohm dummy l oad , VR7 should b e adjusted
to indicate to full scal e meter deflection ,
1 / 2 2/3
with the METE R switch in the PO position .
It should b e n o ted that the PO meter indicates
relative p ower output, and it is not the b asis for
determining actual power output .
VR7 h a s b e en preset at t h e factory to read 1
t o ful l scale into a 5 0 Ohm dummy load . The
2/3
operator should not indiscriminately adjust V R 7
while usin g a n unknown l oad or antenna o f pos­
sibly high VSW R .
PO M e t e r Adj ust
1 6. FINA L AMPLIFIER NEUTRALIZATION
When rep lacing the final amplifier tubes, it m ay
be n ecessary t o reset the bias to give the c orrect
idling current, and to check neutralization. Using
the procedure ou tline d
maximum output and long tube life.
CAUTION
HIGH V O LTAGES ARE
UNDE R S IDE OF THE CHAS SI S AND INSIDE
THE FINAL AMPLIFIER COMPARTMEN T . USE
GREAT CARE WHI LE MAKING ADJUSTMENTS
IN AREA S OF EXPOSED WI RING .
( 1 ) Connect a dummy load to the antenna re­
ceptacle, and set the METER switch to IC.
/ 2
( VR7 ) Accessory Plug
below will guaran tee
P RESENT ON THE
( 2 ) Locate TC0 1 ,
capacitor shaft , on the inside wall o f the
final amp lifier comp artment.
Check the fin al amplifier idling current as
(3)
described in part 7 of this section o f the
manual ( BIAS ADJ USTMENT).
( 4 ) Tune up the transceiver at
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 point of minimum current ( " dip " ) .
I f t h e d ip is n o t prominent, reduce the
LOADING control slightly to get a be tter
dip. As the P LATE con trol is rotated the
meter should rise equally and smo o thly on
either side of the dip .
( 6 ) Determine which side of the dip rises ab­
ruptly. Set the PLATE c on trol slightly t o
this side o f the dip , keep the me ter reading
below 1 00 m A .
( 7 ) Using a n onme tallic tuning wand, rotate the
neutralization c apacitor shaft very slightly
in the direction which reduces the curren t
on t h e me ter. Repeat steps 6 a n d 7 until
the meter indicates a smo oth and equal
rise on either side of the dip .
NOTE : The final amp lifier c ompartment cover
must be in p lace to supply the RF
shielding required during the neutrali­
zation procedure .
Final Amp l i f i e r Compa r t ment
-45-
the neutraliz ation variable
MHz , using
29