3-4 TROUBLESHOOTING CHARTS
2.0 Control Head CM300/PM400 Troubleshooting Chart
2.1 Control Head Failure
Back light
OK ?
Check 9.3V on
Q12, U1 and associated
parts and U8
No
Control Head Check
Power-up
Alert Tone
OK ?
Check Speaker
Connection
No
Indicator
LED’
S
OK ?
Check
Q8-Q10, U8 and 9.3V
No
Display
OK?
Check LCD
connections, U3 for 5V,
Osc. pins 1 & 2 activity
SCI thru via U4
No
Up/Down
P1 and P2
Alert Tone
Buttons
OK?
Check keypad resistors
No
EXT
PTT
OK ?
Check Q13, Q802
No
Communication Ok
Check Q803, Q14 and
associated parts
Control Head is OK
YES
YES
YES
YES
YES
YES
No
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