Repairing Dot Matrix Display

[Niek]

Hello people,

I took my display apart the other day and couldn't figure out how the idea with the pencil is supposed to work. To my opinion the flex cable is made up of two halves of plastic with the printed circuit lines in between the two plastic halves. Therefore to be able to redo the connections simply by drawing on the plastic is (I think) impossible. Has anyone else had any luck with this repair method (Noz?)?
I'm currently toying with the idea to buy very thin electrical wire and actually soldering all connections over with new lenghts of the wire. (very small so I'm not sure it's possible)

[xmexclusive]

Hi Niek, Noz and All

I have taken 5 LH displays to bits a while ago and found all 5 were different and all used different LCD's and driver components. only one had foil connectors that could use the pencil technique. I did not find sufficient compatible components to start swapping bits as a repair method which was my intention. One of these days I will have another go.

Regards

XMexc

[Peter.N.]

I wouldn't try it myself, and I'm a TV engineer (retired) I havn't actually tried repairing one of these, but the general concensus of opinion seems to be, to increase the pressure on the edge connections.

Peter.N.

[xmexclusive]

Hi Peter

Thanks for the advice. I am playing with scrap displays not ones from my cars. I have been looking at grafting in a more modern display as these are now cheap, standardised and potentially reliable. The average working life of Mk2 displays was around 2 years before the line failures set in. Many Mk1 displays are still going strong. This suggests to me that the contact fixes will not last long. I recognise that this is not an economic use of my time but it would be a nice challenge to achieve.
As I want to keep at least one XM until it becomes a classic I need a permanent solution not a repair. Even a new display from Citroen is not likely to last as long as I will want it to despite the unreasonable cost.

Regards

XMexc

[noz]

Hi all,

I've only had a modicum of success by increasing the pressure on the connector strip. The last 4-5mm of the strip is solid with the remainder being flexible. The weak point for the connector strip (ribbon cable) is just at the solid/flexible junction. At that point the tracks break. I have not found a suitable method to fix them.

I thought about the silver paint used to repair rear heated windscreen heaters but you'd need to apply it with the tip of a hypodermic needle.

That was the reason for my call for spare displays to practice on.

I'm disappointed to hear that there are several different types. It makes coming up with a universal fix that much harder.

We do need to find a long term and practical fix for this problem as it afflicts all XM owners. I'm sure if we found a reliable fix we'd be inundated with requests.

Time to get the old thinking caps on methinks.

Cheers

noz

[xmexclusive]

Hi Noz

My thoughts are to find a current standard display that will fit in the case and run it with a micro controller that can also be programmed to respond to various configurations of input lines. That is make it display all the required messages on the work bench then progressively get it to respond to each individual models signals. I would learn to programme micro controllers in the process.
On a par with retro aircon and 2.5 clutch, still I am collecting the bits for those too.

On a slightly different tack my controller ( who like yours can count the number of XM's around the place) has just rejected the grey leather and chammy seats in the V6 and wants them changed for black leather which I just happen to have in the shed.

PS how far have you got with the MK1 workshop manual. I have an collection of XM owners manuals. Any tips on how to go about scanning them. As you can see my computer skills dont get as far as putting the list of cars after my name.

Regards

XMexc

[noz]

Hi XMexc,

The display I have on th ebench for practice has two distinctly different forms of input. The first is very straightforward. There are 30 pins or so on the back and if you earth each one in turn you get a message on the display. The last two pins carry something called VAN (Vehicle Area Network). This carries the RDS info from the radio to the display. The receiving chip is an NEC pic. There are two more NEC controllers to operate the dot matrix.

I too am currently trying to teach myself pic programming so that I can both decipher the comms and, ultimately, write my own messages to the display.

S1 workshop manual is in the same state as it was. I've scanned 4 volumes (1280 pages) but there are at least 9 volumes in total. I've been trying to negotiate with someone who has all 9 volumes but its taking a bit of time. I called him tonight to give him a reminder and he has promised to send them to me.

Cheers

noz

[xmexclusive]

Hi Noz

Thanks for the update, will be so pleased when it emerges. Interested to see we have similar thoughts on the displays. I will see if the supplier of my five will part with some of the remainder in his two buckets full of naff ones.

Regards

XMexc

[noz]

OOh yes please !