Yaesu FT-901DM Maintenance Service Manual page 77

SERVICING
COUNTER UNIT IC INSTALLATION NOTE
In some FT-901 transceivers, Q2920 and Q2r921
were changed from type MSM40192 to type
MSMS5503. The units are identical in operation, but
the MSM5503 pin layout is the reverse of that of
the MSM40192.
For this reason, if you have to replace Q2920 or
Q2o21, be sure to observe the proper alignment of
the key marking, as shown in the drawing below.
Note also that the circuit board is marked correctly
only for installation of the MSM40192 IC. Install
MSM5503's with the key mark at the opposite
end, as shown below.
DISPLAY BOARD
| For models using MSM40192. Circuit board print
7 is marked correctly.
t BOARD
| i
For models using MSM5503.
Install reversed from
o z
PCB marking.
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