[Boatanchors] Re: ft 757 problem

Tue, 30 Jul 2002 21:42:22 +1000

Hi Ray and the list,
A lot of Liquid Crystal displays have the connections to the display made
through two thin strips of conductive rubber that also act as shock
absorbers for the display. If you are able to lift the display out of its
mounting and clean BOTH top and bottom of each  rubber strip with Methylated
spirit (Alcohol) and also the area where the rubber strip makes contact with
the display you may solve your problem. The rubber strips have to be put
back into place very precisely or the little conductive paths in the rubber
strip will not mate with its contact pad on the board on one side and the
contacts on the back of the display on the other side.
If you watch the display carefully and apply gently pressure along the edge
of the display (while powered up) you may see the various segments in the
display switching on and off as the display is flexed.
Be very careful, and if not used to working with fine detailed work take it
to a service agent.
Michael Harley, Curator "The Radio Shack" Caboolture Historical Village,
Brisbane Australia.
----- Original Message -----
From: "Ray Friess" <[email protected]>
To: <[email protected]>
Cc: <[email protected]>; <[email protected]>;
<[email protected]>
Sent: Monday, July 29, 2002 4:24 PM
Subject: [Boatanchors] Re: ft 757 problem


> The ft 757gx has a lithium battery in it.  would this battery be used in
the
> tuning/frequency control/memory functions?   If so, would it cause the
problem
> by going weak???
>
>
> W1EOF wrote:
>
> > Ray,
> >
> > You have an intermittent connection. Could be an IC socket, a connector,
or
> > a broken trace on the PC board. This is what I would do:
> >
> > 1. Remove the cover and power the unit. Attempt to duplicate the problem
by
> > gently tapping in different areas. I don't know the layout of this rig.
It
> > might mean tapping on the circuit bd on bottom, then on top, etc. Try to
> > isolate the problem to one major area of the radio.
> >
> > 2. Look carefully at IC sockets and connectors. You can very often
narrow
> > down a problem by simply looking, or I should say studying the radio.
Look
> > for tarnished pins, connectors, etc. Also look for an area of the PC
board
> > which has an accumulation of rusty-looking gunk. Sometimes stuff gets
> > spilled down into a radio and it takes awhile for the stuff to rot
through a
> > PC board land. In your case I would start in the area around the digital
> > freq controls, the microprocessor, etc. Very often these chips are not
> > soldered in, but are plugged into sockets. Great if you need to replace
the
> > chip, terrible in long-term use due to tarnish on the IC pins and/or
> > sockets.
> >
> > 3. If the visible portions of the IC legs look tarnished, they must be
> > cleaned. Carefully remove them. Find something that you can lay the pins
on
> > to support them, but NOT bend them. This could be a thin tabletop or
> > something like that. Use a pencil eraser to clean off the pins by
brushing
> > away from the IC body. Same thing with connector pins.
> >
> > 4. Another common source of intermittents is a broken land on the PC
board.
> > This can be found by gently tapping, or gently applying pressure to
slightly
> > bend the PC board. If you find a land that is broken, you can easily fix
it.
> > Use an exacto-knife to scrape the conformal coating off the copper
material
> > about a .25" to .5" in both directions. This must be done carefully so
that
> > you don't strip the copper of the board, or cause more problems. Use a
small
> > soldering iron and tin a very small gauge wire. Wire-wrap wire is ideal
for
> > doing this kind of repair. Bend the wire so you have a long piece to
hold on
> > to, and a short/tinned piece that will be long enough to cover the
section
> > of copper you stripped. Once you have the wire tinned, use the iron and
hold
> > it against the copper. Remove the iron and you should now have a
"bridge"
> > that goes across the break in the copper foil. Ue small cutters to clip
the
> > wire that did not get soldered. Two points I cannot stress enough here:
> >         You have to solder the wire down quickly. Too much heat will
pull the
> > copper off the board.
> >         Make sure you do not short this run to an adjacent one.
> >
> > After you care done, carefully inspect your work to ensure a good
connection
> > with no shorts.
> >
> > Power on the radio and try tapping around in the same area. Hopefully
you
> > are done and can button-up the radio and get back on the air! Hope this
> > helps, let us know how what you found.
> >
> > 73,
> >
> > Mark W1EOF
> >
> > > -----Original Message-----
> > > From: [email protected]
> > > [mailto:[email protected]]On Behalf Of Ray Friess
> > > Sent: Monday, July 29, 2002 12:09 AM
> > > To: [email protected]; [email protected];
> > > [email protected]; [email protected]
> > > Subject: ft 757 problem
> > >
> > >
> > > I have a problem with a yaesu ft757gx I'm hoping someone can help me
> > > with.
> > > The frequency display keeps going in and out....  when it goes out I
can
> > > no longer
> > > change frequency with the vfo dial or with the frequency step switch.
> > > It's an intermitten problem that happens at times when the case is
> > > tapped on...
> > > Any suggestions?
> > > Ray  WA7ITZ
> > >
> > >
>
> _______________________________________________
> Boatanchors mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/boatanchors