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[W4AJF]

Hi all, I have an Icom IC-751A with a bad Logic board but the battery tested at 3.19VDC. I swapped the logic board for a good one I had and the radio worked fine. Anyway, with the bad logic board the display reads crazy frequencies and some of the controls don't work and there is no transmit or receive. Does anyone know know if I can get this logic board to work properly?

Thanks for any help.

Adam Farber W4AJF
Cooper City, FL

[W3PX]

That's a sign that the volatile memory on the RAM Unit board has been lost. Probably the old battery was removed and a new one installed without applying a temporary "keep alive" voltage to the board to keep the memory safe during battery replacement.

The easiest solution is to purchase an IK2RND, PIEXX, or Willco replacement board.

Is this the same IC-751A I helped you with a few weeks ago?

73 Frank W3PX

[VR2AX]

Wonder if it's the original battery/board. Sometimes a battery replacement op goes bad and the volatile memory is lost or corrupted. Icom's only fix was to send the board back to the factory for re-programming. That spawned the aftermarket boards from Piexx, Italy and a few others which had non-volatile memory ICs. The only other possibility that I can think of from what you have posted (assuming both battery and memory are fine) would be to check continuity from the various ports of the bad board to the PCB. Scott Malcom (MTS) was the go to person although I recently checked his website and seems he is retiring.

[W4AJF]

Hi Frank, I posted but it did not show. This is ANOTHER IC-751A and your post makes perfect sense and I am sure what you said was exactly what happened. I'll buy a RAM board. Thanks again, Adam W4AJF

[W3PX]

Hi Adam,

OK and good luck with the radio. I've used both the IK2RND and PIEXX boards myself and was happy with both of them. The Willco board has a lot of memories, many more than I would ever need or use. I've never tried one but they have a good reputation as well.

73 Frank W3PX

[K7LZR]

Look for intermittent solder connections on the logic board at the pins which connect to the RAM board. I repaired two IC-745 radios which both had this problem. In both cases, the RAM boards were the Piexx replacement boards and so no problem there but connections between the RAM and logic boards were intermittent.

Solution was to resolder all of those connections and no problem since. That was about a year ago.....