This is my very first post ever. On any forum. I hope I'm not stepping on anyones toes...
About a year ago I agreed to fix the broken screen of a friends Koko H2O. By that time I had successfully repaired an Icarus8 and several smartphone screens and I thought the most tedious part would be to wait for the new screen to arrive from China... Well I made my bet without knowing anything about infrared touch screen technology and the wonders of water-proof assembly with double-sided tape. To change the screen was easy, but even after a good dozen of tries I couldn't get the touch screen to work properly and for a device with just one button that is a no go.
Eventually I gave up and felt bad about it ever since, until I got another broken H2O on ebay for parts to start over. This time it worked out.
I thought I could post a little step-by-step in case anyone needs to change a broken screen, not wanting to go through the whole learning experience. I am sure there are other ways to do it and comments and corrections are welcome. I am only documenting what I have done.
overview
Spoiler:
I hope these drawings will help you understand what I'm talking about. The Aura H2O is quiet the stack of layers. For the touch screen to work pcb and light guide have to be lined up perfectly, but they are not connected directly to each other. That is what makes changing the screen so difficult.
Tools and materials
• An old credit card-shaped plastic card cut in half lengths-wise. The classic guitar pick is useful too. Avoid metal. It's too easy to damage plastic parts.
• Some kind of heat-gun to soften the adhesive. Not strictly necessary, but makes it much easier. (<10€ on ebay)
• WD40 and paper-towels to clean off the adhesive (if you know about a better solvent I'd like to know...)
• IPA to clean the surfaces before putting on new adhesive
• Small Phillips screw-driver
• A razor blade or an exacto knife
• Your new screen of course. Always check the part number on the ribbon cable of your old screen. Mine was ED068OG1 (about 30€ on aliexpress)
• One sheet of A4-sized 3M 300LSE double-sided adhesive (5€ on ebay / aliex)
part 1 : taking it apart
Spoiler:
1. Gently heat up the front cover all around to soften the adhesive. Use one hand to feel the temperature as you go. Before the front cover gets too hot to touch it with your bare hand switch off your heat gun.
2. Try to find an opening between front and back cover with your thumb nail or plastic card. Make your first opening all around the outer edge of your reader. You only need to go 3-4 mm deep to split front and back cover. It won't come off yet. That's normal and will only happen in the next step. You might get stuck as the adhesive cools down again, so add some heat.
3. Heat the front cover up again. Go around the outer edge for a second time. This time you will need to reach further inside. You need to push in between front cover and light guide (aka bezel, but I'll stick with light guide) until you reach the bump of the light guide. If all goes well you end up with the front cover completely removed.
4. Now it's time to remove the light guide from the screen. You need to work from the inside out, sliding your tool between light guide and screen. Start at the bottom of the screen were the adhesive strip is the largest. Apply heat if necessary, but be careful the light guide is fragile. Try to lift it evenly on all sides, keeping it horizontal. There are very small plastic pins on the four corners that you don't want to break off. Once you are done you'll have the bare screen in front of you.
5. Take out the screw in each of the four corners and lift up the screen / pcb assembly. Lift the top first and drag the bottom behind to work your way around the usb connector.
6. Turn the extracted part around to face the pcb. disconnect battery, screen and front light. the battery disconnects by gently lifting the back side of the connector. The screen is the largest connector. You need to lift the plastic squeezer at the back of the connector, the you can pull out the ribbon cable. The front light connector is just under it and works like the screen connector. You can change the screen without disconnecting the battery, but I find it much easier to clean everything after completely removing the pcb.
7. There are 6 screws holding the pcb to the aluminum back plate. Unscrew them and take off the pcb.
8. By now only the (broken) screen is attach to the aluminum back plate. Once again this is done with double sided tape. One strip in each corner (in the picture the screen is already taken off, but you can see the position of the tape). Separate screen and plate by sliding the credit card between them and pushing it against the tape. Heat can help soften the adhesive (do NOT heat the battery !). Be careful not to cut yourself at the edge of the screen, especially if it's shattered.
9. Congratulations, you have successfully put everything to bits...! I'd like to tell you the hard part is done, but noooo. Time to clean all the adhesive : back plate, inside of the front cover, light guide inside and outside and the rim of the back cover (not in the pictures, but needs cleaning none the less...). The inside of the light guide is easy. Usually you can peel off the whole tape in one piece. The rest is messy. Soak the adhesive in WD40, scrape it off with a credit card. Wipe the surface off with some more WD40 until there are no traces of adhesive left. Now you need to clean the WD40 with IPA or simply lots soap and water. Dry thoroughly afterwards. The cleaning is really important. For the most part, double sided tape is really all that's holding your reader together, especially the light guide for the touch screen. Alignment and thickness of the different layers matter. In my experience the only way to get it done is to clean and start with fresh adhesive.