Sounds like my Micronta 22-191 DMM uses the same tape technology to connect its display.? I think the traces are vapor-deposited low-temp solder, and the tape
was fused to the pads with BRIEF application of heat.? Once a critical trace breaks, it’s all over.? Thanks for the ribbon cable/conductive goop suggestion, I’ll try it sometime.
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Dave Wise
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?
No, you definitely wouldn't want to try soldering to the LCD's
glass substrate.
The tape is a terrible idea, because like virtually all contact
adhesives, age makes the tapes get goopy, and loses contact.
Since you probably have nothing to lose, what I would try is to
find a ribbon cable with the correct spacing, and using mechanical
means, align the stripped ribbon with the LCD... then apply a dot
of conductive paint/glue to each wire to glue it to the glass on
the LCD.
-Chuck Harris
On Sun, 5 Sep 2021 22:42:48 -0500 "Dave Casey" <polara413@...>
wrote:
> Yeah, I've got the same problem of failing old tape, but mine has the
> tape directly between the LCD and the circuit board. I imagine I'd
> wreck the LCD if I tried soldering to it.
>
> Dave Casey
>
> On Sun, Sep 5, 2021 at 10:32 AM Chuck Harris <cfharris@...>
> wrote:
>
> > The TI-84 family has the LCD mounted to a circuit board,
> > using a strange tape/cable to stick to the finger contacts
> > on both the LCD circuit board, and the CPU circuit board.
> >
> > Over time, the tape loses connectivity, and some/all of the
> > rows and columns on the matrix display disappear.
> >
> > I did my first such repair on my son's TI calculator, and have
> > since done it on two others. It is a very common problem.
> >
> > -Chuck Harris
> >
> >
> > On Sun, 5 Sep 2021 03:00:05 -0500 "Dave Casey" <polara413@...>
> > wrote:
> > > Chuck -
> > >
> > > Are you able to solder directly to the back of the LCD, or are the
> > > TI-83/84 a board-to-board connection?
> > > In my case (a TI scientific calculator, not a graphing
> > > calculator), the tape strip is board-to-LCD.
> > >
> > > Dave Casey
> > >
> > > On Thu, Sep 2, 2021 at 4:17 PM Chuck Harris <cfharris@...>
> > > wrote:
> > >
> > > > On TI-83's and 84's, that the kids use in school, I just
> > > > solder 36 pieces of wire wrap wire onto the edge connectors,
> > > > and let it be ugly in hiding. That is what TI did on the
> > > > prototypes.
> > > >
> > > > -Chuck Harris
> > > >
> > > >
> > > > On Thu, 2 Sep 2021 15:16:48 -0500 "Dave Casey"
> > > > <polara413@...> wrote:
> > > > > On a related note, anyone know of a source for the tape
> > > > > equivalent of a Zebra strip? The one I have that's failing is
> > > > > a 36 conductor 1.2mm (not 1.27) pitch strip of tape that
> > > > > connects the LCD to the PCB. I could probably replace it with
> > > > > a flex circuit from OSHPark and some 3M 9703, but that's
> > > > > probably more trouble/expense than this old calculator is
> > > > > worth.
> > > > >
> > > > > I have tried heat and pressure on the old flex to some
> > > > > effect, but I've hit a point of diminishing returns.
> > > > >
> > > > > Dave Casey
> > > > >
> > > > > On Wed, Sep 1, 2021 at 9:06 PM Harvey White
> > > > > <madyn@...> wrote:
> > > > >
> > > > > > The neat part of it is that you can get some misalignment
> > > > > > and it will still work.
> > > > > >
> > > > > > Take that rubber, put it over a matrix of contacts, put
> > > > > > keypads over it, and you have an elastomeric keyboard.
> > > > > >
> > > > > > Harvey
> > > > > >
> > > > > >
> > > > > > On 9/1/2021 9:26 PM, Jeremy Nichols wrote:
> > > > > >
> > > > > > Ahh. Thank you.
> > > > > >
> > > > > >
> > > > > > On Wed, Sep 1, 2021 at 5:11 PM Harvey White
> > > > > > <madyn@...> wrote:
> > > > > >
> > > > > >> Take little carbon particles and put them in what's
> > > > > >> effectively foam rubber. Measure from one side to another
> > > > > >> without compressing it. You might be getting a high ohms
> > > > > >> reading. Now compress the rubber. This causes the
> > > > > >> particles to contact each other, but only where the rubber
> > > > > >> is connected. This makes a lower resistance.
> > > > > >>
> > > > > >> Now take two printed circuit boards with connector fingers
> > > > > >> (easier to see that way). Where there are fingers, you
> > > > > >> get a conductive region from top to bottom. Since the
> > > > > >> rubber is not compressed from side to side, it doesn't
> > > > > >> conduct that way.
> > > > > >>
> > > > > >> This allows glass with conductive fingers (the LCD glass)
> > > > > >> to be connected to the PC board fingers. Most of the
> > > > > >> conductivity is between compressed points, or at least,
> > > > > >> vertically.
> > > > > >>
> > > > > >> Harvey
> > > > > >>
> > > > > >>
> > > > > >> On 9/1/2021 7:41 PM, Jeremy Nichols wrote:
> > > > > >>
> > > > > >> Pardon my ignorance: I looked at the web site and was none
> > > > > >> the wiser. What are these things used for?
> > > > > >>
> > > > > >> --
> > > > > > Jeremy Nichols
> > > > > > 6.
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