Icom IC-740 Common Questions page 4

Probable
Causes:
Cure:
Symptom:
Probable
Causes:
Cure:
[ICOM Homepage] [Dealers]
�1997 ICOM America, Inc. The ICOM logo is a registered trademark of ICOM, Inc. All ICOM radios significantly exceed FCC
regulations limiting spurious emissions. All stated specifications are subject to change without notice or obligation.
operating range of the radio. Rotating the VFO knob may cause
strange characters to appear in the display. Radio does not work
properly. Cycling the power switch a few times may restore operation
temporarily, or radio may be stuck in the failure mode.
1) CPU is glitched and must be reset. 2) Loose connector on logic or
matrix unit. 3) Bad diode on matrix unit.
Turn-off memory back-up switch on rear panel of radio and leave
radio unplugged for a few minutes or so to reset CPU. (It is
recommended that the switch be left to the OFF position to prevent
future failure.) Re-seat all connectors on logic and matrix unit. If
none of these solve the problem, there may be a bad diode on the
matrix unit.
Either of the following: 1) Preamp does not work. Sensitivity of radio
drops when preamp is engaged. 2) RX noisy and intermittent. Preamp
intermittent.
1) Bad preamp relay on RF unit. 2) Burned components in preamp
section on RF unit. 3) Cracked solder on RF unit in preamp section.
Replace bad RL1 (FBR221DO12). Replace bad/burned preamp
components on RF unit, usually RL1, Q11, Q12, R58, C86, etc...
Also check Q10 for failure. If bad, replace it with a 2SC2878B.
Carefully examine the preamp section of the RF unit for bad joints
and resolder as needed.
FAQ Index Page
[New Radios] [Calendar] [Specials]
| Amateur Radios
[Get In Touch With ICOM ]