[ICOM] Problem with IC-751a Display

[Marc & Tricia Niebergall]

It's fixed. But I must admit it was a two fold problem, one of which I
unknowingly created while fixing the other. I am now certain that the root
of the erratic display and related symptoms was due to the row of loose
contacts on the logic board. This had been causing intermittent problems
for months. It became permanent in the last few days.

Now the rest of the story. Some time while taking the logic board out and
re-installing, I damaged a ribbon connector. I was unaware of the problem,
but it was creating different display symptoms and confusing me. After
hours of troubleshooting I discovered the error. I had to solder in 5
jumper wires to bypass the damaged ribbon, but the repairs worked and it is
operating perfectly. This however was further complicated when I discovered
that the Icom memory board had a 17m issue. The Willco board works fine.
This was a tough problem but I feel it is finally solved.

Thanks for all the suggestions. They are all very helpful

Marc

On Sat, May 19, 2018, 5:05 PM VAN van Bergen <wd6fgb at digitalpath.net> wrote:

> Have you put it thru a Factory Reset since all these repairs?
>
> -----Original Message-----
> From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net]
> On
> Behalf Of Marc & Tricia Niebergall
> Sent: Saturday, May 19, 2018 3:47 PM
> To: ICOM Reflector
> Subject: Re: [ICOM] Problem with IC-751a Display
>
> 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
> >>
> >
> >
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