I lived with it until late 2014, when I took the switch apart to find nothing wrong with it. Since I was going to incorporate the light into the switch for my soldering station, I hooked it up to the switch it was going to be connected to and used that, until I couldn't hack the light back on after it turned off.
The next day I removed the wires from the switch and soldered them together, which eventually yielded the same result of the lamp turning itself off. I think I measured the voltage from the adapter and found that it was working fine before directing my attention to the head of the lamp. I think I found the head hot to touch, so I knew something was definitely wrong.
At some point I opened up the head and found a PCB with three things on it: an LED and two SMD parts (SOT-223 case) - I wasn't sure what to make of it as searching the numbers on the part yielded nothing. As I look back now (now that I've learned quite a bit), they more than likely are voltage regulators connected to regulate the current to the LED, and it's more than likely that one of the regulators became bad or was bad to begin with.
Back then though, I figured the LED was being over-volted (where 4 volts was too much), and played with it with my bench-top power supply to find that I could definitely power it with less voltage. I set it aside because I didn't want to spend any more time with it, and it sat for a few months before I decided to do something about it.
About the middle of last year, I decided to look at it again, and I had forgot what voltage output of the original adapter and started at 9 volts, which blew one of the regulators. I think I grabbed the adapter and looked at the voltage and decided to find a good voltage under 4 volts. Anyway, I found that 3.3 volts would definitely be doable, and then looked for a 3.3 voltage regulator.
Then came the next problem, I would need to find an adapter that met the minimum input voltage (and amperage) for the voltage regulator, but luckily I had one that was more than plenty. I could have used an LM317T voltage regulator, but I wanted the modification to take up as little space as possible (not to mention that I'd need an input of at least 1.5 amperes.
I drilled three holes into a small potting box that I found at work (I'm not sure if the potting boxes were used for something or not at one point) before stuffing the wires through and soldering the wires and regulator legs appropriately. I attached the regulator to the top-inside with an insulating shoulder washer and a 4-40 x 1/4" screw and a nut. Luckily I had also found a bottom for the box, which I had fastened to the base of the lamp with double-sided adhesive foam.
The regulator attached to the top-inside of the potting box, better picture with flash, the bottom "lid" affixed to the base, and the box "secured" to the base.
At some point before this, I had grabbed the other lamp as sort of a cross-reference and while it did get warm, it wasn't scalding like this one was. Anyway, because of the adapter that I used to power the regulator and the lamp, I decided to use this for the dim light for my bedroom (usually used before I go to bed). It worked just fine, though it was a bit dimmer than I expected, until I left it on for a while, to which it turned off again.
Needless to say I was confused again, and I looked at the lamp with the regular light on. I found that the regulator was putting out a lot more heat than I had expected and it melted the plastic some. Since I immediately investigated, the plastic and screw were still hot.
The outside and inside of the potting box where the regulator was. (Picture was taken after the new case was completed.)
Luckily I found some scrap aluminium alloy blocks and an unused aluminium case as well, both of which I took to use to remedy the solution (along with some electrically-insulating thermal pad scraps and some 4-40 taps). The aluminium alloy was a pain in the arse to drill through, even with a good cordless drill, but I had gotten the hole I needed.
At least I thought I had. The hole I drilled was too large, so the tap wasn't able to do anything. I drilled a smaller hole, which I thought worked, until I broke the tap... Oops. I then looked up the correct drill size and found the closest that I had, which was bigger than the #43 that I needed, but worked just fine.
With the "correct" drill size, I then positioned the block to where I'd like it to sit in the case and drilled a hole through the case and into the block, following up with a slightly larger drill bit through the case itself to allow the screw to pass through.
I drilled a few more holes in the case for the wires and for some slight airflow. The top and bottom are aluminium sheets, since the original top and bottoms were nowhere to be found and I didn't want to spend any more than I already had to buy the proper lids. The top lid received extra holes for slight airflow, while the bottom screw holes were countersunk for use with flat-head screws for easier mounting.
Since I had to remove the regulator from the potting box, I had to redo the soldering a bit, and made it a bit neater when I soldered it back together - soldering both ground wires to one wire to the ground leg (centre leg) of the regulator instead of both ground wires like I had done before.
I mounted the regulator to the block (with the thermal pad between them and using the insulating shoulder washer) then slid the block into the case before securing the block to the case.
The regulator attached to the block, different angle, block secured to the case, extra space inside the case, block spacing from the bottom of the case, the screw securing the block to the case (as well as the output cable), and the air holes on both sides of the case,
I then did a bit of cable management at the top before leaving the rest for the next day.
The next day, I soaked what I couldn't scrape off of the double-sided adhesive foam with Goo Gone while I attached the top and bottom pieces to the case.
Finished top and bottom.
Once the base was clean and dry, I adhered the case to the base and returned it to its spot in my bedroom.
"Near" and "far" sides.
The block and the case definitely dissipates the heat from the regulator without any problems at all - I probably didn't even need the air holes. I did a test where I left it on for several hours and the case wasn't even warm, so it was good to know that I shoddily engineered something that excessively exceeds its purpose.
I think after the metal casing the light is dimmer and maybe brightens over time, but it works out just fine for what I use it for. Maybe I'll properly fix it at some point, or maybe just buy a new lamp (it's about 10 USD each if the prices haven't changed)... Or maybe just leave it be.
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