Reading before going to sleep is something many people do in order to relax and bring down their minds from the hectic thoughts of the day. If you are in possession of an e-reader with a backlight, like the Kobo Glo, this is made a lot easier. However, the backlight of an e-reader may actually be so bright that it prevents relaxing and instead keeps you awake, reading for longer than intended. This is caused by too bright, partially blue light being emitted by the LED backlight. Because of this, while reading, you do not actually become sleepy. The effect is similar to reading with cool white light from your bedside lamp.
Even if you are not necessarily affected as much by the blue light but just by the brightness, it may be possible to replace the LEDs in your e-reader. Now, the post I linked has more pictures attached to it than this one, but I will explain why.
Disassembly
The first few steps of disassembling the e-reader are very simple. A flat, thin, strong object may be used to pry the back of the e-reader open. You can try using your fingernails or possibly a butter knife without a sharp or ragged edge, but when using the latter you should keep in mind that the metal is stronger than the plastic and you may cause scuffs or scratches. After this, you can observe the main (and only) PCB in the e-reader. Interesting features of the board of the older Kobo e-readers includes a serial port header and the storage being provided on an SD card, containing a variant of Linux.
After disconnecting all the cables carefully (take care not to tear or scratch the ribbon cables), unscrewing the four screws holding the PCB will free it from the enclosure, exposing the display assembly. In the case of the Kobo Glo, this display assembly is made of metal and attached to the enclosure with some screws. After removing these you may think that the display assembly freely lifts out.
However, this is not the case. The edge of the display is covered with double-sided tape, making the display stick quite strongly to the front panel of the case. This is also the reason I forgot to take pictures of this part: When removing the screen very, very carefully, the tape makes snapping, almost cracking, sounds. Previously, I had seen a Kobo Mini of which an inner layer cracked, leaving no visible issues until restarting the device. Then, it became obvious that the screen was cracked internally by a line of ‘bleeding’ ink. However, no damage could be observed to the outside of the screen. Thus, removing the screen is truly an exercise is patience and keeping steady hands.
At every snap with which yet another part of the tape let go, I was afraid that I had cracked the screen, either internally or the outside layer. There was just no way to know until the whole ordeal was over. Even though I was extremely concerned with whether the device would still be functional, I kept going. I had come this far, after all.
Then, after freeing the display assembly, the LED strip also turned out to be attached to the screen with very thin double-sided tape. Worse, the LEDs were mounted on a piece of ribbon cable, reinforced only by a layer of white plastic. This made things considerably harder still.
Replacing LEDs
The LEDs are extremely small with less than a millimeter in width. Replacing them is not easy at all, as a normal soldering iron with a pretty big tip will easily melt the ribbon cable, leaving very little room for error. Possibly it is easier to accomplish replacing the LEDs with a hot air soldering iron, but I do not have one on my desk (yet?). So, I took out the finest tip for my soldering iron, steadied my nerves and got to work.
It was basically a train wreck. While removing the existing LEDs, I tore off some of the pads to which they were attached, so I would have to use thin strands of wire to connect some of the LEDs, which were thankfully connected in series. There were five of them, and I broke two pads. That’s not so terrible it cannot be fixed.
The work got more complicated when I melted part of the ribbon cable with my soldering iron when trying to attach the new LEDs. I had chosen the Bivar SMS1105YC, as they are right angled, have the right colour and are pretty dim. They are, however, slightly thicker and smaller than the original LEDs, which turned out to be a minor issue later. Attaching the new LEDs was significantly harder than removing the old ones, as I had expected. I had not expected, however, to do so badly that in the end I would have five LEDs and four thin strands of wire (I used single strands from a CAT5 ethernet cable) connected to the ribbon only by the two pads at the extremes.
Result and Recommendation
For re-attaching the LED strip to the LCD, I used a fresh piece of very thin double-sided tape. The front glass of the screen had slight indents where the LEDs were supposed to sit. However, the model of LED that I chose turned out to be a little bit too thick to sit comfortably in these indents. This did not affect the fit of the screen in the case, but it did create some unevenness in the light distribution of the screen. Putting the e-reader back together after that is very easy in comparison.
The end result was definitely worth the trouble. The light is very easy for the eyes and actually I sleep a lot better after reading on my e-reader now. The light actually makes me more sleepy. Now, if you want to read the whole night and stay awake with your favourite book, this is properly not the effect you want. But if you want to fall asleep after reading more easily and don’t want to replace your e-reader with one of those new fancy models with adjustable colour temperature backlight just yet, then this mod can be interesting.
However, given the difficulty of it and the potential to break at least the backlight but possibly the whole screen of the e-reader, I do not recommend it unless you don’t mind having to buy a new e-reader if something does go wrong. As for me, I think I will go to sleep early tonight, but not before having read a chapter or two.