Icom IC-746 Pro for sale

[Randy Smith]

Hello,

I have for sale an Icom IC-746 Pro; covering HF, 6, and 2m. It comes with the box, manual, power cord, and hand mic.

This is a later 020 model, after Icom had addressed the IC-151 failure issue.

This radio had the display back light failure. Transistor Q302 on the S-Logic board controls the current through the voltage inverter circuit that powers the cold cathode fluorescent back light. There's insufficient thermal transfer from the transistor footprint to the copper plane on the PCB to adequately heat-sink this component. Running the display at less than 100% brightness increases the heat produced by the transistor and, in some cases, the transistor will fail.

Replacing the transistor on the existing PCB footprint could have led to the same failure again. To preclude this, a small PCB, manufactured on an aluminum substrate for maximum thermal transfer, was designed and the new transistor mounted to it. The new PCB was then attached to the metal frame of the shield around the power supply circuit which provides a much greater heat-sink capacity than the original PCB. Measurements with a thermal camera indicate a temperature rise of less than 15 degrees above ambient with the display set to minimum brightness. Due to the heat generated in this constrained area by the previous transistor, the nearby electrolytic caps were also replaced.

Here's the shield frame with the aluminum substrate PCB and transistor installed.

Here's the rig in operation after repair. The overall image is a little dark due to insufficient lighting in the room and the illuminated display caused the ACG of the camera to reduce gain. The rig is in very good condition with just a few minor cosmetic flaws.

The radio is available for inspection and/or a test drive if you're interested. I'm posting to this group first in hopes of a local sale. Asking price is $725 or best offer. Contact me via this email address.

Thanks,

Randy - N3XA