MobileRead Forums - View Single Post - Touch screen modification on PRS 700 for improved clarity and contrast

gokalp · 02-27-2009, 11:22 AM

I was posting my progress in the disassembly thread, but I figured it might be a good idea to form a separate thread for the touchscreen modification. So here is the breakdown, I have accidentally damaged the touchscreen on my PRS 700 trying to clean the dust spots. Sony told me that the replacement panel would be $199.38, so I tried modding the reader with a standard resistive touch panel.

It turns out that the loss of contrast in the screen is mostly due to the digitizer, which also forms the topmost protective layer. Its texture is pretty matte to prevent reflections.

I have ordered a 6.4" resistive digitizer from Mouser:
http://www.mouser.com/Search/Product...4DJrRFjNIx0%3d
It's $29.92, but it transmits 86% light compared to the standard 80%. One problem though, since it is 6.4" and not 6". Hence, it will not fit unless one would trim the sides by a couple of millimeters, which not so easy as the panel is glass. Here is datasheet for the digitizer family: http://www.fujitsu.com/downloads/MIC...rd_ds_rohs.pdf
and the datasheet for the specific model:
http://www.fujitsu.com/downloads/MIC...-0554-t048.pdf.

The panel has arrived, and it required a little bit of retrofitting. I knew that the cable was the same as the original Sony panel, both in terms of size and cable arrangement. However, when I opened the device I saw that in the last centimeter, the cable gets smaller and plugs into a miniature connection. Anyways, I cut the original cable, cleaned up the protective plastic and soldered both connections.

Note that I also cut the front plastic, only the gray bezel (i.e. the frame with the text "home", "search" etc...) remains. This also improved the screen.

The panel worked immediately, even without any calibration. And after the calibration it became even better. A couple of observations, the panel is on glass, it is glossy and it is *very* clear. It works excellent with a finger, and not so much with the stylus, as I think the stylus cross section is too small to register as a touch.

I tried putting the panel behind the reader, facing the back cover. It works, and it is not really difficult to operate, but it also registers a lot of false touches while holding the reader, so I gave up on that. However, I really like the clamshell type design, where I can move the digitizer to the back when needed.

BTW, when the e-ink screen is exposed without any transparent sheet, the lighting does not work. However, the external digitizer fixes this problem perfectly, and even enhances the light uniformity. Originally the reader has a clear light gradient which made the center darker. This is due to the reflective surface being too close to the screen. With the external digitizer, the space between the screen and panel increased and this made the light much more uniform.

So here are the pros and cons of the flippable touch panel:
Pros:
- Excellent clarity and contrast without the touch panel, as much as 505
- Much better clarity and contrast with the touch panel compared to original design.
- Touch panel very easy to operate with finger, this includes slidebars and keyboard.
- Much better light uniformity with the touch screen.
- Much easier to remove the dust

Cons:
- panel does not fit in the front recessed section as it is 5mm larger on either side (which makes this mod flippable)
- glossy touch panel means it might create reflection problems in certain situations. (but you can flip it over to read with the digitizer stored on the back)
- Stylus not working with the digitizer.
- Light dies not work without a panel on the front of the screen (i.e. digitizer or a clear plastic sheet)

Here are some pictures if anyone is interested.

The screen clarity with and without the bottom part of the original digitizer:
Note that in this picture, the left side has the bottom and top digitizer, however the right on only has the top screen.

The screen with the digitizer stored in the back:
Here I cut the top screen such that only the gray bezel remains.

The illumination without and with the external panel:

The reader with the touchscreen on, and an image of the ribbon cable.

02-27-2009, 11:22 AM	#1
gokalp Member Posts: 23 Karma: 13 Join Date: Jan 2009 Device: sony prs 700	Touch screen modification on PRS 700 for improved clarity and contrast I was posting my progress in the disassembly thread, but I figured it might be a good idea to form a separate thread for the touchscreen modification. So here is the breakdown, I have accidentally damaged the touchscreen on my PRS 700 trying to clean the dust spots. Sony told me that the replacement panel would be $199.38, so I tried modding the reader with a standard resistive touch panel. It turns out that the loss of contrast in the screen is mostly due to the digitizer, which also forms the topmost protective layer. Its texture is pretty matte to prevent reflections. I have ordered a 6.4" resistive digitizer from Mouser: http://www.mouser.com/Search/Product...4DJrRFjNIx0%3d It's $29.92, but it transmits 86% light compared to the standard 80%. One problem though, since it is 6.4" and not 6". Hence, it will not fit unless one would trim the sides by a couple of millimeters, which not so easy as the panel is glass. Here is datasheet for the digitizer family: http://www.fujitsu.com/downloads/MIC...rd_ds_rohs.pdf and the datasheet for the specific model: http://www.fujitsu.com/downloads/MIC...-0554-t048.pdf. The panel has arrived, and it required a little bit of retrofitting. I knew that the cable was the same as the original Sony panel, both in terms of size and cable arrangement. However, when I opened the device I saw that in the last centimeter, the cable gets smaller and plugs into a miniature connection. Anyways, I cut the original cable, cleaned up the protective plastic and soldered both connections. Note that I also cut the front plastic, only the gray bezel (i.e. the frame with the text "home", "search" etc...) remains. This also improved the screen. The panel worked immediately, even without any calibration. And after the calibration it became even better. A couple of observations, the panel is on glass, it is glossy and it is very clear. It works excellent with a finger, and not so much with the stylus, as I think the stylus cross section is too small to register as a touch. I tried putting the panel behind the reader, facing the back cover. It works, and it is not really difficult to operate, but it also registers a lot of false touches while holding the reader, so I gave up on that. However, I really like the clamshell type design, where I can move the digitizer to the back when needed. BTW, when the e-ink screen is exposed without any transparent sheet, the lighting does not work. However, the external digitizer fixes this problem perfectly, and even enhances the light uniformity. Originally the reader has a clear light gradient which made the center darker. This is due to the reflective surface being too close to the screen. With the external digitizer, the space between the screen and panel increased and this made the light much more uniform. So here are the pros and cons of the flippable touch panel: Pros: - Excellent clarity and contrast without the touch panel, as much as 505 - Much better clarity and contrast with the touch panel compared to original design. - Touch panel very easy to operate with finger, this includes slidebars and keyboard. - Much better light uniformity with the touch screen. - Much easier to remove the dust Cons: - panel does not fit in the front recessed section as it is 5mm larger on either side (which makes this mod flippable) - glossy touch panel means it might create reflection problems in certain situations. (but you can flip it over to read with the digitizer stored on the back) - Stylus not working with the digitizer. - Light dies not work without a panel on the front of the screen (i.e. digitizer or a clear plastic sheet) Here are some pictures if anyone is interested. The screen clarity with and without the bottom part of the original digitizer: Note that in this picture, the left side has the bottom and top digitizer, however the right on only has the top screen. The screen with the digitizer stored in the back: Here I cut the top screen such that only the gray bezel remains. The illumination without and with the external panel: The reader with the touchscreen on, and an image of the ribbon cable. Last edited by gokalp; 02-27-2009 at 11:24 AM.