|HP 35s modification: Matte LCD cover (and LCD re-alignment)|
Message #1 Posted by Dallas Osborne on 8 Sept 2009, 4:39 p.m.
Replacing the soft, glossy 35s LCD screen cover with a matte version (and fixing LCD alignment):
The new screen material should be about 0.5-0.7mm thick. I used LCD protectors out of a batch of office telephones I found in a dumpster (Lucent multi-function jobs). They were nice and large, 0.7mm thick acrylic with a nice subtle matte surface on one side, gloss on the reverse. You may also find this type of plastic at a custom framing shop and it is available from many vendors online (e.g., http://www.rplastics.com/polycarbonate-film.html). To attach the new screen in place on the front panel I used Scotch double sided tape. A double-sided foam boarder is normally attached to the back side of the screen to make firm contact with the LCD. I had planned on using the 3M 4492 (black, 1/32Ē (about 0.8mm), double-sided adhesive foam), but found I could slowly remove the old one and recycle it. It is important to reapply this; it will keep dust out and provide positive pressure to the screen. When measuring and cutting the new material, cover the plastic with a clear tape that can be easily removed to protect from minor scratches. Obviously, make sure the area between the new screen and the LCD is free of dust and other particles; it is very annoying to finish the upgrade only to find there is a nasty piece of lint hanging in there.
Photos (these are huge, by the way; it may take a bit of a wait for them to load in some locations): HP 35s Screen Mods
Intro over, the process is as follows:
1. Open the case by removing the batteries, four round rubber screw covers, and the long rubber strip at the bottom of the back half of the case. Put them aside in a safe place. I would suggest sticking a strip of tape on your work surface and put them there; it will be dust-free and release the adhesive easily.
2. Remove the screws and put them in a safe place.
3. Using finger only, slowly pry the case apart along the top and left side with the face down at the work table. Be careful not to tear off the power wires between the two halves; they are on the side of the calculator under the ENTER key.
4. Remove the springs at the top and bottom (the top one is obviously the long spring) and put them in a safe place as well. If you think you should just leave the springs where they are and be careful with the front half, I would suggest you grab a flashlight for when they fall out on the floor.
5. Remove the rubber reset seal and put it away. This is the white/clear round thing that may have fallen off when you opened it up. It will usually stay attached to the reset hole on the back half of the case. (In case you may be tempted, donít mess around with the black carbon contact part.)
6. Slowly lift up the LCD by using a non-scratching tool. Allow the adhesive to slowly free up. If you pull to fast things will end up messy. I used the handle of a plastic fork. Flip the LCD out and over the PCB, wrap it and the PCB with a soft, lint-free cloth, and tape it all together.
7. Press out the old screen by starting at one corner and S-L-O-W-L-Y let the adhesive give way to firm, slow pressure.
8. Cover the new, matte screen material with removable clear plastic tape on both sides and apply the old screen to the new matte (front) side. This is your template. Cut around it. Donít worry about the blade-cut space; there is enough room in the case for the new one to fit even with a few tens of mils additional material.
9. Remove the tape from the back side of the new screen. Wipe it down very carefully with a lint-free cloth. Carefully remove the foam gasket from the old screen and place it on this cleaned surface. If the old one is torn or stretched out in the process you will need to make a new gasket. I suggest 3M 4492 tape (1.5Ē width will be adequate to make a new one). Single-sided foam tape will work just fine as well and would be easier to open up later, if you need to.
10. Remove the tape and old screen from the front side of the new screen and
wipe it down.
11. Carefully lay new double-sided tape on the edges of the new screen at a width that will allow it to be placed in the front of the case and make contact only to the inside plastic: slightly less than 2mm. As you can see from the last picture, I put a little too much width on the bottom of the one I did and it can be seen when looking in at an angle.
12. Carefully install the new screen. (If you have a crooked LCD, see the note at the bottom.)
13. Check/clean any dust.
14. Take off the cloth and tape from the LCD and lay it back in place.
15. Put the springs back in place.
16. Put the rubber reset button back on its post.
17. Carefully close up the case (making sure the power wires route around the reset post and contact), screw it together, and check the new display.
18. If the case creaked a lot during operation, this is a good time to test out the loose points, apply small dots of adhesive (epoxy, hot glue, anything else you may like) at the key locations and close it back up. I would warn against trying to tighten the screws as a solution; the posts butt up together and wonít go any furtherÖ and plastic is soft.
19.!Test the reset button!
20. Replace the rubber screw covers and enjoy the matte screen.
One final note: If you have a 35s with a crooked display, this is a perfect opportunity to tilt it back into place. I didnít take pictures of the entire procedure, but here we go: After you pop out the old screen, put the batteries back in and push the LCD back into its socket; turn on the calc and type in a ton of 8ís. Take a close look at the margin for mental reference. The idea is to bend/press/mold the right hand portion of plastic up, as seen from the back side of the LCD socket frame, (for most early 35sí that is). This may require gentle nipping at the bracing buttresses with a pair of side cutters. Then shim the LCD and screw post on the lower right. Double check the alignment and shift it around as needed. Make sure the other side of the screw butt will not knock the shim around and put a spot of glue to hold the shim in place. There is a shot of the shim in one of the photos.
Edited: 8 Sept 2009, 9:57 p.m. after one or more responses were posted