[Premium-Rx] RF-590 display

[Barry Hauser]

I don't have an RF-590, but do have some W-J's with those electoluminescent
vacuum displays.  No problems with them so far.

However, used to run across the same problem with old electronic
calculators.  Worst case is that all the segments lit up displaying a string
of 8's.  More often there was some glow to the segments that were supposed
to be unlit which made it diffucult to read reliably.

It seemed this was usually "an outside job" -- the display module itself was
good, but there were faulty contacts, a bad solder joint, or in some cases a
bad component.

Try tapping lightly on the board if you can get to it with covers removed
and watch the display for flickering.  There may be a ribbon connector or
header with a high resistance connection.  Find them and reseat them -- use
some contact cleaner if necessary.

There are some kinds of faults that develop during storage -- like light
oxidation or electrolytic action from the assembly of dissimilar metals.
(Not totally avoidable with gold plating either).  Another possibility is a
bad capacitor.  For example, in the '70's they started using a lot of dipped
tantalum caps which 10-20 years later proved to be problematical.  You may
have a localized supply voltage problem due to a component that aged badly.

Again, I don't have one of these -- is there a trimmer pot or two somewhere
in the display assembly?  This type of display works with some kind of
threshold voltage or bias supply as I recall.  Might be too high, or you
could have the opposite -- a poor ground.  If you see any leads going to
ground lugs or grounding points for the display assembly, loosen and
retighten as there can be some light oxidation.  Remove and reseat plugin
boards, if applicable.

Could also be the pins on the display module itself.

Worth a try....

A tinted filter as suggested, is another possibilty.  Some of the calculator
displays relied on a dark green filter to keep the "unlit" segments fully
invisible.  BTW -- Older LCD displays had a narrow readable angle of view
and if tilted slightly were hard to read.  Some relied on a polarized
plastic lens -- without it, they were invisible altogether.

Barry



> On Thu, 21 Nov 2002, Gary Mitchelson wrote:
>
> > The RF-590 I just bought is my first RF-590. I don't know if the diplay
> > problem I am seeing is normal or not. For a quick background on this
> > RF-590, it had sat in it's original Harris box since it was new (1989)
> > for 10 years in a warehouse. Then it was unboxed and used occassionally
> > until I bought it last week.
> >
> > The displays are not clear e.g. the unused segments and digits have a
> > slight glow. Is this normal? I adjusted the brightness but that just
> > makes it to bright. I have the brightness set to about 1/3. The original
> > owner said it's been like this since first taken out of the box.
> >
> > Gary
> >
>
> A temporary solution I used on another piece of gear was to put a darker
> piece of plastic over the display, and turn the brightness up.  I don't
> know if this would apply to the 590 - I have Racals with LCDs.
>
>                                   73,
>
>                                       - Steve - W5EGP
>
> ******************************************************************
> *   Steve Linscott           Information Technology Division     *
> *   linscot at rice.edu      Rice University       Houston, Texas   *
> ******************************************************************
>
>
>
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