YAESU FT-757GX

RF Unit: Transmitter Circuits


A. ALC Meter Zero Set

With the transceiver tuned to 14 MHz, USB mode, and with no
microphone input, key the transmitter and adjust VR1008 to the
threshold point where ALC just starts to produce meter deflection
(METER switch in ALC position).


B. TX IF Transformers

At 14 MHz, CW mode, with the METER switch set to ALC, preset
VR1006 to the center of its range. Press the MOX switch and adjust
T1020, T1021 and T1023 through T1025 for maximum deflection on the
ALC meter. If no deflection is found at first, set the METER switch
to PO and the rear panel FWD/REV switch to FWD. Return the METER
switch to ALC when the PO indication is maximum. If the ALC
indication is overscale, reduce the setting of the DRIVE control.


C. TX Power

At 14 MHz, CW mode, set the DRIVE control fully clockwise and
adjust VR1006 for 100 watts output (10 watts for FT-757SX).


D. PO Meter

At 14 MHz, CW mode, press the MOX button and adjust the DRIVE
control for 100 watts output on the external wattmeter. Set the
rear panel FWD/REV swith to FWD, and with the front panel METER
switch set to PO, adjust the FWD SET control for internal PO
meter indication of 100 watts.


E. SWR Turndown (Automatic Final Protection)

At 14 MHz, CW mode, connect a 16.6-ohm dummy load (three 50-ohm
load in parallel) and a thru-type wattmeter to the antenna jack.
Rotate the DRIVE contrl fully clockwise, press the MOX button,
and adjust VR1007 to the point where power indication on the
wattmeter just begins to drop.


F. CW Sidetone Level

With the AF voltmeter connected across the speaker terminals,
in a CW mode with a key connected, close the key and adjust
VR1004 for 0.3 V sidetone output on the meter.





LPF Unit:  Directional CM Coupler Balance

Set the METER switch to PO and the rear pane FWD/REV switch to
REV. Set the transceiver to the CW mode, and transmit a 14 MHz
carrier into the dummy load. Adjust TC3001 for minimum deflection
on the meter.




PA Unit:  Idling Current

Remove the jumper shown in the following figure, and connect the
DC milliampmeter (500 mA range) in place of the jumper. With the
transceiver set to an SSB mode and with no audio applied to the
transmitter, close the PTT line and adjust VR6001 for 250 mA
(+/-100 mA) on the ampmeter. Replace the jumper after the
adjustment. For the FT-757SX, adjust VR7001 for 150 mA (+/-50 mA).


Qeulle: YAESU MUSEN CO.,LTD