[ICOM] Problem with IC-751a Display

[Ken Winterling]

Marc,

I would carefully recheck your soldering work and look for solder bridges.
It is also possible you disturbed a connection(s) during your repair effort.


On Sat, May 19, 2018 at 18:47 Marc & Tricia Niebergall <mtniebs at gmail.com>
wrote:

> 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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-- 

Ken
WA2LBI

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