Broken scanner

04.05.2011 20:52

Maybe a month ago, before Zemanta moved into a new, more spacious office, I accidentally snatched our flatbed scanner by its cable and pulled it to the floor. It wasn't the first time this happened, but for the first time it landed on its USB connector. The impact forced the cable and a small piece of PCB with the female USB connector well inside the space traversed by the scanning head. Since this rendered the scanner useless for business use it ended up on the top of my pile of broken but potentially still useful stuff.

The other day I took it apart to see what can be made of it. It's a Canon CanoScan LIDE 25 based on the National Semiconductor LM9832 "Merlin" scanner-on-a-chip. Just to make it clear what kind of hardware I'm talking about: this particular model currently runs for around $50 on I think it wasn't much more expensive when we first bought it.

Canon CanoScan LIDE 25 scan head

Not surprisingly, everything inside it is dedicated to reducing costs. This is the first device that I disassembled that was held together by Scotch tape! There isn't a single screw inside. The glass plate is latched to a single-piece plastic shell. Two small strips of plastic on the longer sides prevent it from getting loose and are glued to the glass with sticky tape. These strips can be simply peeled off and then all further disassembly is obvious (this project has some more disassembly instructions).

The little PCB that was causing the problem (you can see it in the back on the photo above) seems to do nothing more than connect the USB via the flexible flat cable to the scanning head. Apart from the sticky-tape this cable seems to be another weak point of this design. At some point in time it got nicked and now every time the head move it gets squashed against the sides. I'm guessing the varying resistance this causes doesn't do wonders for the linearity of the head movement. Nor for the longevity of the fragile cable.

The head itself also contains the microswitches for the buttons at the front of the scanner - when the head is anywhere else than in the extreme top position the buttons don't push against anything. Also of interest is the fact that underneath the glass plate is a black-and-white calibrating strip. The head seems to look for that before starting a scan so the scanner won't work without the glass plate in place.

Posted by Tomaž | Categories: Life


Thank you so much for posting this. I had a Canon LiDE 200 stop working and because of your post I was able to recover it. LOL at the tape. I couldn't believe it. I honestly thought the scanner was impregnable until I saw this.

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