Psion Series 5MX disassembly and screen cable repair


A common fault occurred with my Psion 5mx today which had me very worried as I hadn't taken a backup for a couple of days and I'd done a lot of work on it. Despite faultless use earlier in the day I flipped open the Psion to find horizontal lines staring at me on the screen. This problem happens when the flexible plastic ribbon cable which connects the motherboard to the screen cracks. A hole in the plastic which is used during the manufacturing process to hold the cable in place is a weak spot and years of flipping the Psion open and closed causes a fracture around this hole. As soon as the fracture cuts through one of the signal conductors, you can kiss your Psion display goodbye.

The only real fix to this is a new cable. As a temporary measure I managed to bodge mine to get my Psion working again while a new cable was on order. I managed to take a backup of the Psion despite no screen (I found that opening the lid about a centimetre caused the display to function correctly so that I could flip through the menus and switch on the remote link - phew!)

Here comes the disclaimer.....

This is a very tricky procedure, both in terms of the actual disassembly and the repair. Unless you have a fine-tipped soldering iron and you are very good with soldering and handling tools, I really would not recommend this. It's not for the faint hearted - it's downright open-Psion surgery. Use these instructions as a guide - and attempt to follow them at your own risk.

1. I hope you have a recent backup as you will need to remove the main and backup batteries. You will also need to remove the three arrowed screws using a jewellers screwdriver. One screw is under the warranty sticker (if you have a warranty on your Series 5, you're going to void it by following these instructions).

2. With the screws removed, flip open the Psion and remove the lower half of the casing (pull from the rear of the unit first).

3. Close the Psion and pull off the battery compartment - be careful of the connectors inside. You may need to prise it over the two clips toward the top-centre.

4. Undo the three screws holding the motherboard in place.

5. Disconnect the speaker ribbon cable by lifting out the tags on the sides of the connector and gently pulling the ribbon free.

6. You should now be able to carefully prise out the motherboard part way.

7. Flip open the unit for better access to the ribbon cables. The blue cable carries the keyboard signals while the brown cable connects to the screen. Disconnect these cables in the same way as the speaker cable earlier and remove the motherboard.

8. With the unit closed, release the spring hinge from the rear centre......

9. ...... and unhook them from the ends. Careful not to snap any of the ABS casing!

10. Slide the screen from the chassis.

11. Use a knife to slide out the plastic peg holding the keyboard to the screen on each side. Remove the keyboard.

12. Now that the screen unit has been separated, gently slide the LCD section down and out of it's surround.

13. Unclip the lower part of the LCD surround and remove it.

14. To remove the metal shielding from the screen (if fitted), prise out the tags around the edges on the rear.....

15. ..... and remove the back of the screen casing.

16. This bit is very delicate (and isn't usually necessary). The glass touchscreen can be removed from the LCD panel. The application icons are stuck to the glass with glue but some gentle teasing should allow you to pull the glass off. I did this to remove a mark that had developed on my LCD, but ordinarily this step is not necessary.

17. Remove the sticky black plastic from the solder points of the ribbon cable. The arrowed hole is usually where the point of failure occurs. The fracture may be minute (I needed a magnifying glass to spot it at first) but look carefully and you'll likely see that a track (or tracks) near this hole have split. In my case the split has affected one adjacent track.

18. Time for a temporary repair. Replacement cables are available but I needed a quick fix. Firstly I got hold of some replacement ribbon strip from an old duff CD-ROM drive.

19. Next I carefully cut off one of the end conductors.

20. I soldered one end of the strip to the point on the rear of the LCD that the failed track had connected to.

21. I then folded the new strip around to the opposite side of the cable (not ideal but the solder points on each end of the original ribbon are on opposite sides).

22. The other end of the new strip was stripped of insulator with a knife and the conductor carefully soldered to the opposite end of the original broken track. These solder points are tiny and my first two attempts didn't work due to minute solder splashes shorting out the adjacent points. Using a magnifying glass I ran a knife between the points to clear out any splashes and checked it with a continuity tester. On the third attempt the Psion powered up and my screen was back (and I checked the backlight worked too!).

Finally, before reassembly, I used a hot glue gun to try and prevent some of the movement around the solder joints of the new cable and around the dodgy hole to prevent more splitting.

How long will this fix last?

It lasted about four days for me. I carry this thing everywhere and I'm always flipping it open but the repair just wasn't up to these daily strains.

 

The only way to cure this problem is with a new ribbon cable. Note also that the 5mx uses a different screen ribbon to the Series 5. We don't sell the replacement ribbon cables as parts or carry out the repair but you can find somewhere that does here.


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