[ICOM] Re IC765 No Transmit

[Gary Fiber]

Mike

if you look at Q14 and find it defective then there are a whole lot of 
parts that can be stressed even if they check ok. First is about Q14 and 
the 2nd write-up tells you what to look for on D47.
If D47 voltages are incorrect it was the writer technicians experience to 
change all the components listed even if they checked good as they would 
fail in a short time after the original repair was made by replacement of 
one or two components.

Gary K8IZ


Symptom: No TX output in all modes. Problem is traced to no output at J8 
connector on the RF unit.
Probable Cause: Bad Q14 transistor amplifier on RF unit.
Cure: Replace faulty Q14 transistor (2SC2053).
Remarks: There may be other problems on the RF unit. Check the DC voltages 
at D47 diode.

Symptom: No or very low RX sensitivity.
Probable Cause: Bad components on RF unit, probable result of RF overload 
or lack of necessary update. Check DC voltages at D47 diode on RF unit to 
verify problem.
Correct voltages are: Cathode side- RX: 8.5 V, TX: 13.8 V. Anode side- RX: 
9.0 V, TX: 9.5 V.
Cure: Replace these components on the RF unit: D42, D44, D45, D46, D47 
diodes, Q15 transistor. Check C174 and C179 capacitors for leakiness. There 
may be other failures. Unit is not repaired until listed voltages at D47 
diode are correct.
Remarks: If the serial number of the unit is below 01800, the unit probably 
needs a factory update to the main unit to prevent future failure of these 
components. Call technical support for details on this update.


Gary Fiber K8IZ
GROL PG-19-6691
Washington State Resident