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Repair/mod - bathroom light

Problem

A new cabinet for the bathroom was bought, featuring a pair of halogen lamps. The switch was on a box housing the electronics, inside the cabinet, requiring opening its door to be accessed. Not exactly user-friendly, and also the switch itself was a non-sealed plastic kind not protected against ingress of water. That's possibly why it was located in so poorly accessible location.

One day, when the light was powered on, a quiet sound was heard from the box and the light did not light up. A weak smell of electrical troubles lingered around for a while.

Solution

The box was taken apart fairly easily. Some screws were holding it to the cabinet, some more screws then were holding it together and few more were there for an internal baffle that kept the wiring in place. A switching power supply of a common kind was found inside the box.

The power supply board was easily accessible. Visual examination of the inner surface of the casing shown a scorch mark on the white plastic. Examination of matching area of the power supply circuitboard revealed an exploded SMD resistor; several more with less obvious damage were found nearby. From their placement in the circuitry the suspicion goes to the power transistors; one or both are suspected shorted, the resulting overcurrent then being responsible for the damage of the passive parts, and the SMD resistors acting as fuses and preventing further damage, not even tripping the breakers.

Instead of messing with the board repair, a new power supply module for a halogen lamp was sourced. The replacement module was well-housed, contained soft start and overheat protection, and was small enough to fit into the original box without either having to be modified.

So far for the repair.

When the whole shebang was in parts, it was decided to address the switch location issue too. A fairly large rocker switch with a backlight was sourced, together with a suitable plastic box. A transparent rubber cover for the switch was also used, to protect it from the environment, namely from water on users' hands.

A hole was cut into the box and the switch was set in. Two lengths of a two-wire cable were attached to its contacts and secured with heat-shrink tubing. Pairs of holes were drilled into the box on the top and bottom side (top pair for screws, bottom pair for screwdriver access). Wood screws were placed into the top holes. Small pieces of heat-shrink tubing were added to the screws to prevent their slipping out of the holes, for ease of mounting. All seams inside the box were covered with silicone caulking as a level of defense against water ingress. The seam between the box halves was covered with caulking and the box was screwed shut.

The switch box was mounted on the bottom side of the cabinet; two holes were drilled into its bottom, then the screws were put into the holes and tightened. The screwdriver access holes then were covered with a dab of silicone caulking.

The cables from the switch were pulled behind the cabinet, into the top side area where the power supply box is located. Using a piece of a terminal strip the switch was connected in series with the original power switch, in the way that its built-in neon bulb is permanently lit. This allows easy finding of the switch even without switching on the main light.

With some tribulations and redoing (in order to get the cables into the correct holes in the box), the replacement power supply, the terminal strip, and all the wiring were stuffed into the original enclosure, which was then mounted back to its original place.

The risk of electric shock should be mitigated by several levels of water insulation of the wiring and switch. The caulking and other insulation measures should prevent contact with live electricity even in case of dripping-wet hands; a situation markedly improved in comparison with the original switch.

The user experiences so far are greatly positive. No more opening the mirror-door cabinet in order to switch on the light above the sink, no more hand-prints on the mirror.


Casing, inside (note scorch mark)

Casing, outside

Casing, outside

Old power supply

Old power supply

Old power supply, visible damage of R5 and R8

Wiring inside the cabinet

Wiring at the top of the cabinet

Replacement power supply

Additional switch parts

Panel hole prepared to be cut

Panel hole cut and deburred

Switch mounted in the box

Switch mounted in the box, caulking added

Sealed switch box

Switch location

Mounting holes

New wiring, replacement PS

New wiring, replacement PS

New wiring

New wiring, closed enclosure

New wiring, enclosure in place

New switch location

New switch, lighted

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