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Archive for July 3rd, 2013

HP ScanJet 3970 Lid Hinge Re-Repair

As expected, that repair didn’t last very long at all; one hinge fractured along the same line as before. This time, however, we had a visit already in-plan, so I brought along my solvents and clamps.

Perhaps you wondered how I could have been so remiss as to not brace those thin white flanges. One picture of the unbroken hinge in the “lid down” position is worth a thousand words:

HP 3970 Scanjet - intact hinge

HP 3970 Scanjet – intact hinge

Need more? Here’s another thousand words from the other side:

HP 3970 Scanjet - intact hinge pivot

HP 3970 Scanjet – intact hinge pivot

As the lid opens, the gray tab pivots toward the edge of the lid until it’s nearly parallel, at which point all of the force tries to yank those two flanges apart and then crack the tiny solid part at the pivot pin.

Eventually, it succeeds. This is a view of the scanner base with the gray tab inserted in its slot, with the broken hinge in the “lid up” position:

HP 3970 Scanjet - broken hinge pivot

HP 3970 Scanjet – broken hinge pivot

Clever design, no?

I was unable to extract the broken fragment from the gray tab (actually, unwilling to apply more force, as I cracked part of the gray ring around the hinge pin), so this became an in situ repair. Once again, I applied solvent glue and squished the pieces together:

HP 3970 Scanjet - glued hinge

HP 3970 Scanjet – glued hinge

And clamped it while we ate lunch:

HP 3970 Scanjet - hinge clamping

HP 3970 Scanjet – hinge clamping

The brass rod applies the clamping force to the fractured part of the hinge through the pivot point. This isn’t the most stable clamp arrangement you’ve ever seen, but it worked well enough.

I pushed the scanner back half a foot, so the lid now clunks against the wall just before the hinges reach their limit. Maybe they’ll survive until the next visit…

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