Thanks for the posts folks. I had a good look at the schematic and I'll try
various suggestions.
Looks like the fan will run from the 12 volt power rail with a 330 ohm
resistor in series.
The IC-735 has discrete transistors. That should make troubleshooting much
easier
than dealing with surface mount devices.

73, Bernie

"Scott Dorsey" wrote in message
...
Bernie Murphy wrote:
The fan in my trusty ICOM 735 has stopped working. This is the small
squirrel cage fan that cools the PA heatsink when the radio is
transmitting.
Has anyone ever had a fan failure? The fan itself spins manually. I
called
ICOM Canada and they indicated that ICOM no longer stocks parts of this
type
for the 15 year old 735. The failure could also be caused by the control
circuit in the ICOM 735 that turns on the fan at different speeds
depending
on the temperature of the PA heatsink.

I would bet a control circuit failure. Measure the voltage across the fan
and see if there's anything there. I bet there is not.

If the motor has failed, you will probably not see DC continuity across
it either.

While you have it open, put a drop of turbine oil on each of the motor
bearings so they stay good.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."