Yaesu FT-757GX II, Техническое дополнение

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CW Filter Isolation
In some sets prior to Lot
6,
IF signal leakage has
been found to occur around the CW filter during
CW-N reception with the FT-757GX. The cause o f
this problem is insu fficient isolation within F M
detection subsystem IC 01022 (MC3359) on the RF
Unit during CW operation. To remedy this
problem the following modification will remove
the supply voltage from FM 2nd IF signal bu f fer
01021, except during FM operatio n. This
modification has already been carried out i n all sets
from the beginning o f Lot
6
onwards, as well as in
some o f the later sets in Lot
5.
1.
Disconnect the power supply, and remove the
bottom cover o f the transceiver to gain access
to the component side o f the RF Unit.
2. Re ferring to the drawing below, cut jumper
wire R near the end closest to VR1010 and
VR1011. Splice a 3 to 5 cm length o f hookup
wire to the free end o f the jumper, and solder
and care fully tape the splice.
3. Now connect the free end of the extended
jumper to the cathode of diode D 1064 (near
VR1003 ). The cathode lead o f this diode is the
upper (exposed) lead.
4.
Replace the bottom cover and reconnect the
power supply. This completes the modifica­
tion.
(make on
"X"
over +8V)
_...FMSV
RllOI IOOk!l
Cll51 O.OlµF
RllOO lk!l
RF UNIT
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