Introduction
A dimmable 12v desk LED magnifier lamp had a faulty friction hinge at the base such that its angular position could not be set.
Disassembly showed that inside the plastic bracket was a metal friction hinge that was too stiff causing damage to the plastic surround. The friction hinge (or torque hinge) was lubricated with silicone grease and its screw adjusted, such that by trial-and-error, there was enough friction to position the lamp to the required angle.
A new nut and bolt were used to compensate for the damaged plastic bracket.
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Shows general view of 12v LED desk lamp with magnifying lens. Red arrow shows location of damaged hinge. (Green arrow shows location of touch sensitive dimmer switch)
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Undo 4 small screws (yellow arrows shows locations) to split the plastic bracket in two. This needs a small Philips Jewellers screwdriver with pliers on the screwdriver as they may be difficult to extract.
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Second image shows the bracket with the stem (orange arrow) removed and one side of the bracket removed to expose the friction hinge (blue arrow).
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The image shows the friction hinge which can be pulled out of its hexagonal housing. (note bit of broken off white plastic in hole).
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The square section should rotate inside the large hexagonal section (use a vice or equivalent). If it is too stiff, undo the small nut and washers and put some silicone grease in the gaps and work it in. You can adjust the friction by tightening the small nut to different torques on re-assembly.
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There is a bit of trial-and-error involved to get the right amount of friction so may need to also re-assemble the lamp a few times so the stem holds its position.
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Depending on how much damage was caused to the plastic bracket by the 'tight' friction hinge, it may be necessary to replace the original small (6mm) long screw with a larger (18mm long) through bolt and nut.
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This would involve drilling/filling a clearance hole right through the bracket and friction hinge to big enough to take the bolt, so the worn pieces can be clamped together. Keep the broken piece of white plastic in the friction hinge, widening the hole, to make a good fit.
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You may need a wedge with a hole in it to use as a washer as the nut tightens onto a curved surface. (I used half a cord grip from a mains plug).
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There may be better solutions for repairing broken plastic eg a build up of superglue and sodium bicarbonate or 3D printing a new part.
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Friction hinges in lamps may need periodic adjustment else damage can occur to surrounding materials particularly if they are made of plastic.
