Icom IC-251A Instruction Manual page 38

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DRIVER UNIT TRANSISTORS
RECEIVE
TRANSMIT
BASE COLLECTOR | EMITTER | BASE COLLECTOR | EMITTER
TR No. | "or OR OR OR OR oR |REMARKS
GATE1|GATE2| DRAIN | SOURCE IGATE1|GATE2| DRAIN | SOURCE
NOTE:
Other devices work in C-MOS level and with pulse signals, so the voltages can not be measured
' with a 50KQ/V multimeter.
The function of the CPU is identified with reading the relationship between the R output and the
K input signals.
Refer the timing chart of the R output signals on the next page. The relationship between the R
output and the K input signals can be checked with a dual trace oscilloscope, and also the level of
— these signals can be measured with the scope.
The driver unit consists of several C-MOS IC's and P-MOS IC's. P-MOS !IC's are IC9 TMS1115 CPU
and 1C10 TMS1024 I/O port, and the others are C-MOS IC's.
Refer to the following threshold level chart for measuring these levels.
THRESHOLD LEVEL CHART