What is inside a Chip Display?

[Robsey]

I am just going to give a brief over-view of a typical chip display as fitted to standard Cavalier radios.

Grundig SC303,
Philips SC201,
Philips SC804...
and possibly the CD300, but it is too long ago since I had one to remember if it had a detachable display.



Part number 90 418 560.

As suspected it is a very simple item which can be stripped down as follows.

First turn the display face down on a clean surface.

And remove two very tiny cross-head / Philips size 0 screws.






You then need to run your thumb nail along the split across the top and bottom of the casing to tease the two shell halves apart.

The front facia unclips to give this



Then slip the complete internals out from the rear casing.

[Robsey]

The internals of the display is wrapped around a white plastic body.



The display screen and colour filters are clipped to the front by four hooks / tabs.

And the circuit board is clipped to the rear by four hooks / tabs.

Be careful teasing the tabs open, as the plastic is quite old and brittle.

Once the internals are separated out, you will end up with all this.



This is the display end.



And this is the three tiny lights on the circuit board.



I have zoomed into all the tracks of the ribbon cable, and all the solder joints, but I could not see why this particular display did not work properly, with missing and ghosting of the display text.

So this is where I hold my hands up and say that I have no idea how to fix it.

But - for the time being, I have rebuilt it and put it away with my other duff displays.

[Robsey]

At least you do not need to pull yours apart, and risk breaking it.

I hope you find it useful, even if it is just to deal with your own inquisitiveness.

[Mk3alan]

Interesting!
Rob, how is the ribbon cable connected to the glass? display?
The display in my Astra has a ribbon connector which uses conductive rubber pads for display communication which is compressed onto the back of the glass display which looks like it has been 'printed'? with a conductive edge connector.
This works well, to start with, but after 20 years the rubber 'connector' loses some of its rubberyness and hence connection resulting in lost pixels.

Alan

[Robsey]

The dual info display, and board computer both use the "rubbery" strip method.

This ribbon almost looks bonded directly to the glass, which I am sure that it probably isn't.





I will have a closer look in due course.
I am surprised that there isn't a repair video on YouTube...

Just need to get my car back from the garage, before I can test the display.
I have cleaned and checked all internal parts and connections.

[Robsey]

I have looked at the screen more closely.

It is made of three laminated layers.

A filter layer,
Glass Panel
And a LCD / Digitiser panel.

The layers appear to be very well bonded together.

Did you know,?...
If you turn the filter layer back to front, you will get illuminated text on a dark background.
This was briefly a bit of a fad with dual info displays circa 2009 / 2010.

[Mk3alan]

I am under the impression that as well as the 'rubbery' part losing some of its flexibility there is a potential for poor contact to the glass?
If it was a PCB edge connector it could be cleaned with a fibreglass pen to restore continuity.
Not sure what could be done with the glass, contact cleaner?

Alan

[Robsey]

What is odd is that the ribbon appears to stop short of the LCD panel.

Check out the updated images above.

[Mk3alan]

Looks like magic!
I think the glass has had an 'edge connector' vapour deposited onto it which provides the
conductive circuit for the LCD

Alan

[Robsey]

I have looked into how display panels can be separated, however all info appears to relate to smart phone and tablet displays.

They all mention that the displays are bonded using "LOCA", which is Liquid Optically Clear Adhesive.

Methods for the separation process vary from "Don't bother, it isn't worth the hassle",
to
Warm the display to 80°C to soften the adhesive, and then gently ease a waxed playing card between the panels.
Some people suggest using Isopropyl Alcohol as a lubricant, and to prevent the panels sticking back together.

I remember years ago easing a razor-blade between the plastic filter and the glass display panel.
This was to reverse the text and background colours of a dual info display as mentioned above.

The board computer is nigh on impossible, because of the glued on legend also being there.

Anyway...
The idea of separating two thin fragile glass panels sounds just a bit too risky for me.

[Mk3alan]

Doing nothing sounds the best route!
Not quite the same on the Astra but I increased the pressure, very slightly to improve contact on a spare display assembly I bought as a guinea pig.
It broke, quite delicate.

Alan

[Robsey]

Well I tried the faulty display in my SC303.
(One of James' old radios).

And it stayed faulty, so I decided to have a play and turn the filter layer over.
(But I buggered it up in the process).

With no filter at all, you just get a blank illuminated display.

Filter (now even more damaged) fitted as intended.



Reversing the filter in the display looks like this.



And the display as it appears when plugged into the radio



And just to prove that neither James' radio nor Dave P's display were damaged by my bumbling...

[Robsey]

And just to confirm,

If you get a "display" message on the screen, then you just need to input the security code in the usual way.

Ignition power on.
Turn radio Off.
Hold [AS] pressed and turn on the radio.
Do not release [AS] until you see the word "Code"

Wait for message "10 _ _ _ _ "
Input Code as follows.
Press preset [1] repeatedly for 1st digit.
Press preset [2] repeatedly for 2nd digit.
Press preset [3] repeatedly for 3rd digit.
Press preset [4] repeatedly for 4th digit.

When happy you have the correct code.

Hold [AS] pressed until the radio springs into life.

Job done

[Robsey]

As for how to separate the filter layer...

Warm the panel to approx 80°C.
(Don't melt one end like I did, hence the pale corners).

Ease the film off with a thin wedge.
I used a fish gutting knife, which was too sharp and sliced the filter twice.

When separated, partially dissolve the glue with baby oil. Massage it in with a finger nail. Wipe with a clean cloth

For stubborn glue use neat washing up liquid. Massage it in with your finger nail.
Wipe with a clean cloth

The glass panel is easier to clean as it is harder to scratch.
I used baby oil on a rag. Not just poured over the glass.
Massage in with a finger nail. Wipe clean with a dry cloth.