Quote:
Originally Posted by nhedgehog
OK, so it was the screen but broken at an unusual part preventing it from showing those classic artefacts we know so well from broken screens.
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That's my hypothesis at this point, yes, although I can't draw a definitive conclusion.
I've looked at replacement screens briefly, but the cost difference with a brand new device in a comparable league is too small to justify spending any time on replacing it. Note that with the replacement screens you linked to, it's still necessary to remove the battery from the screen and the screen from the metal frame & plastic fascia, then remount (glue/tape) these items back onto the new screen. It's feasible, but quite a bit of work especially if it's going to be a one-off repair.
Thanks for the hint on the drive voltage; I doubt this has much to do with it because the malfunction was sudden ("last night it worked fine, but today it won't turn on"). Moreover, there have been no issues with changes in contrast etc which would signify drive voltage problems, and there's no sign (or likely cause) of any defect that would have caused a sudden change in drive voltage. Not to mention that in such a case, the fix would be to remove that underlying cause instead of adjusting the voltage. Given that the voltages generated by the TI chip look entirely plausible, I don't think I'll spend time exploring into this direction.
I did check with my wife and she confirmed she had carried the reader in a different spot in her bag where it's more likely to have been compressed. My guess is that the device flexed a little despite being inside a protective case, breaking the glass at the backside of the screen where it's barely visible.
Here's some shots of the supposed crack in the glass:
Overview with main PCB removed:
A little closer, looking across the flex cable with the touchpadcontroller:
Closer still from the other angle:
What I don't know is (1) whether this really is a crack in the glass; I'd have to remove the metal frame to be sure. (2) If it's a crack, whether or not it happened while I was working on the device - I didn't notice anything, but glass can crack unnoticeably. (3) If a crack in that place would explain total display malfunction. I can see how it might be a good explanation if it extends across all data lines, but I don't know the physical layout of the screen itself.
So some uncertainties left, although I'd say with 95% confidence that this is the cause. In which case, it's not really viable to repair this unit unless I can find a replacement screen for like €10 somewhere.