ft 757 problem

[Ray Friess]

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: owner-baswaplist at foothill.net
> > [mailto:owner-baswaplist at foothill.net]On Behalf Of Ray Friess
> > Sent: Monday, July 29, 2002 12:09 AM
> > To: baswaplist at foothill.net; boatanchors at mailman.qth.net;
> > boatanchors at listserv.tempe.gov; glowbugs at piobaire.mines.uidaho.edu
> > 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
> >
> >

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