Yaesu FT-902DM, Instruction Manual

Page: 46 / 55

M AINT ENANCE AND ALIGNMENT
WARNING
DANGEROUS VOL TAG ES ARE PRESENT
WITHIN THI S TRANSCEIVER. USE EXTREME
CAUTI ON WHEN WORKING ON THE TRANS­
C EIVER WITH THE COVERS REMOVE D . DIS­
CHARGE ALL CAPACITORS BY SHORTING
THEM TO G ROUND WITH AN INSULATED
SCREWD RIVER AFTER POWER HAS BEEN
REMOVE D , AND OBSERVE OTHER NORMAL
SAFETY PRECAUTIONS.
CAUTION
Never operate this transceiver in the transmit
mode without a matched antenna or dummy l oad
c onnected t o the antenna receptacle on the rear
panel. It is possible to d amage the final amplifier
tubes and the pi network components if the trans­
ceiver is operated without the proper l oad termi­
nation.
GENERAL
This transceiver has been carefully aligned and
tested at the fact ory and , with n ormal usage ,
should not require other than the usual attention
given to electronic equipment. Service or realign­
ment of a maj or component may require subse­
quent realignment ; under no circumstances,
though , should realignment be attempted unless
the operation of the transceiver is fully under­
stood, the malfuncti on h as been carefully ana­
lyzed, and the fault has d efinitely been traced to
misalignment. Service work should only b e per­
formed by experienced personnel using the proper
test equipment .
EQUIPMENT REQUIRED
'
( 1 ) RF Signal Generator: Hewlett-Packard Model
606A or equivalen t , with one volt outpu t
a t
S O
Ohms , and frequency coverage to 3 0
MHz .
( 2 ) Vacuum Tube Voltmeter (VTVM ) : Hewlett­
Packard M odel 4 1 0B or equivalent , with an
RF probe good to 4 0 MHz.
(3 ) Dummy Load : Yaesu model YP- 1 5 0 o r equiv­
alent, with 50 Ohm n on-reactive load imped­
ance rated to 1 5 0 watts average p ower.
(4) AF Signal Generator: Hewlett-Packard Model
2 00AB or equivalent .
( 5 ) A general ·coverage receiver covering the fre­
quency range from 3 to 3 0 MHz wit h a 1 00
kHz calibrator.
·
( 6 ) A frequency counter, Yaesu Model YC-5 00
or equivalent, with resolution to 0 . 0 1 ' kHz
and frequency coverage to 30 MHz .
1 . S-METER SENSITIVITY ADJ USTMENT
Place the transceiver in the receive mode and
connect a signal generator to the antenna terminal
of the transceiver. Set the signal generator to
1 4200 kHz with an output of 6 dB. Tune the
transceiver to 1 4200 kHz for a maximum reading
on the S-me ter. The S-meter should just start to
rise with a 6 dB input. If no d eflection is o bserved,
adjust VR4 0 2 to ob tain a slight meter deflection.
Apply 1 00 dB input to the antenna t erminal ;
the S-meter should read S9
+
6 0 dB. If not, adjust
VR4 0 1 . VR4 0 1 and V R4 0 2 are located on PB­
l 7 04C
When the transceiver is tuned to 1 4 200 kHz, the
1 00 kHz cah brator signal will indicate approxi­
mately S9
+
1 0 dB when MARK switch is acti­
vated.
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