[ICOM] Problem with IC-751a Display

[Marc & Tricia Niebergall]

Here is the latest update on the unusual display problem  I am having with
my 751A:

I have been experiencing unusual tuning and display. Sometimes the tuning
jumps around radically with no normal operation. I compared both the Willco
memory board and the original Icom board. At first I was certain that the
Willco board had failed. But after finding a row of loose contacts (memory
board contacts) on the Logic board, I thought I had found the problem.
Well, after resoldering the connections the symptoms changed. Both boards
are acting the same, and the transceiver operates normally, except the
display is stuck and does not move. The transceiver changes bands,
receives, transmits...all functions work except the display shows a bunch
of 8's and 0's. I have powered down and let it cool down, re-powered, and
the problem is still there. I am totally confused as to where to begin.

On Sat, May 19, 2018 at 8:01 AM, Marc & Tricia Niebergall <mtniebs at gmail.com
> wrote:

> Well it seems like I have narrowed down the problem in my 751a. It has
> installed in it a Willco memory board, and when I re-installed the factory
> board the problem all but disappeared. I say because there still exists a
> problem tuning the 17 meter band. The Willco board is totally inop, so I am
> thinking of replacing it with the Piexx brand. Before I do, I would like to
> determine the cause of the 17 meter band not being able to tune. You can
> spin the dial and it jumps to a 17mhz freq and then further spinning does
> nothing. I am wondering if the previous owner installed the Willco board in
> an effort to alleviate this problem, assuming it existed then. Lot's of
> head scratching, but there is light at the end of the tunnel. Any further
> suggestions are most welcome.
>
> Marc
>
> On Fri, May 18, 2018 at 11:06 AM, Marc & Tricia Niebergall <
> mtniebs at gmail.com> wrote:
>
>> Powered up my 751a today and everything worked fine. Shut it down and
>> restarted about an hour later and the display indicated all zero's. The
>> tuning knob had no affect. Neither did most of the other switches. Cycled
>> the power a couple times and it returned to normal. Any idea where I might
>> begin the troubleshooting process?
>>
>> Several months ago, I had a slightly different situation in the display
>> where turning the tuning knob caused a very radical and fast moving
>> display. This turned out to be a loose R-20 in the Logic board. A
>> re-soldering of the resistor cured that problem.
>>
>> So, this is a new symptom and any assistance would be greatly appreciated.
>>
>> Marc-k7wxk
>>
>
>