Linux tip, Fedora tip / howto: Fixing the Epson Perfection 4490 scanner ratchet noise
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Fixing the Epson Perfection 4490 scanner ratchet noise(related tip: using the Epson 4490)
When scanning a heavy book, you may get the following: the scan head stops, and a terrible grinding ratchet sound is heard from the scanner. When you hear this, switch the scanner off immediately.
Even worse, from that moment on you may never be able to scan again without this problem occurring.
It is caused by the fact that on one side the glass plate is supported by three very flimsy plastic tabs, which bend downwards when some pressure is applied to the plate (as from a heavy book).
On this page I describe a possible fix.
Opening the scanner
Some additional info a reader sent to me:
Thank you for pointing out the small clearance between glass & carriage - I had been quite baffled.
However, in my case the glass is still quite well attached to the case. If you push down on the middle of the glass, it is obvious that the case is ridiculously flimsy; the top at the back sags, the sides of the top section twist and the bottom sides bend out and down. Thus, moderate pressure will move the glass bodily downwards; push down on a book spine to flatten the page and you are in trouble!
The carriage guide rod seems to be slightly higher at the front end than the back, relative to the case edge - about 1 mm. I have inserted washers between the case sections at the screw positions 1.2 mm thick; this, combined with more cautious manipulation of the book spine seems to have done the trick. But it's not ideal, as it doesn't address the fundamental lack of case stiffness - an appalling piece of product design.
Incidentally, the much cheaper 3490 model has a completely different case design with a full-depth upper section and is appreciably stiffer.