Yaesu FT-840 Service Manual page 14

Transmitter IF Interstage Transformers
D Connect an in-line wattrneter and 50-Q
dummy load to the ANT jack.
0 Set the RF PWR and VR1010 fully cw (max.).
Tune to 14.200.0 MHz, key the transceiver and
adjust T1016 - T1021 several times for peak
indication on the wattmeter (approx. 100 W).
CM Coupler Balance
D With the 50-Q dummy load connected to the
antenna jack, tune the transceiver to 14.200.0
MHz, and select the CW mode. Connect the DC
voltmeter between pins 2 (-) and 3 ( +) of
J 1022, key the transmitter and adjust TC4001
on the LPF Unit for minimum indication on the
DC voltmeter.
RF Power Output Adjust
D With the in-line wattmeter and dummy load
still connected, set the RF PWR control fully cw
(max.) and VR1010 fully ccw (min.).
D Select CW mode and tune to 14.2000 MHz.
Key the transmitter and adjust VR 1010for100
W ±5 W as indicated on the in-line wattmeter.
SOW RF Power Output Adjust
D Set switch 81001 to the 50
set the RF PWR control fully clockwise (max.).
D Select CW mode and tune to 14.2000 MHz.
Key the transmitter and adjust VR1016 for 50
W ±2.5 W as indicated on the in-line watt­
meter.
Ext. Antenna Tuner RF Power Adjust
D Tum the transceiver off, then jumper TP1002
to chassis ground.
D Set switch 81001 to the "100
then set the RF PWR control fully cw (max.),
and tune to 14.200.0 MHz, CW mode.
D Tum the transceiver on, key the transmitter and
adjust VR1011 for 10 Watts. Tum the trans­
ceiver off, and remove the jumper from
TP1002.
TX
IF Gain
AF
D Connect an signal generator and AF mil­
livoltmeter to the MIC jack, and inject a 0.5 m V
signal at 1 kHz.
0 Set the RF PWR and MIC controls fully cw
(max.), tune to 14.200.0 MHz, USB mode.
D Key the transmitter and adjust VR1007 so that
the meter (set to ALC), just begins to deflect
3-4
(II)
RF
ALC Meter Sensitivity
PO Meter Calibration
Reverse ALC (SWR Turndown)
W
position, then
W"
position,
(increase AF SG level to 1 m V rms, if neces­
sary, to permit deflection).
D The S-Meter Full Scale Adjustment must be
done before this procedure.
D With the transceiver tuned to 14.200.0 MHz,
USB mode, inject 3-m V at 1 kHz from the
generator to the microphone jack (pin 8).
D Key the transmitter, and adjust the MIC control
so the meter, set to ALC,just begins to deflect.
D Increase the injection level to 7.5 mV, and
adjust VR1014 so that the meter deflects to the
top edge of the ALC zone.
D With the in-line wattmeter and dummy load
connected to the antenna jack, tune to 14.200
MHz, CW mode, and press the PO meter selec­
tor button.
D Key the transmitter and adjust the
control for 100 watts on the in-line wattmeter.
Then adjust VR 1019 so the PO meter also
indicates 100 watts.
D Connect the inline wattmeter and a 16.6-Q
dummy load (or three 50-Q loads in parallel)
to the antenna jack, and set the
fully clockwise (max.).
D With the transceiver set to the CW mode on
14.200.0 MHz, key the transmitter and adjust
VR 1 017 for 40 watts on the wattmeter.
1 3
s
S-Meter Reverse PO Indication
FT-840 Technical Supplement
AF
RF PWR
RF PWR
control