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Thursday May 27, 2010

Flashlight Rebuild

Previously I wrote about building a P60 drop-in from some different component parts. The P60 format is designed for that kind of tinkering. But when I bought the LED for that drop-in, I also got a second one just like it and looked around for a home. I thought I could put it in the AKOray K-106 3-mode programmable light I got earlier and had already taken out its LED and installed a brighter Cree XP-G R5. But when I did that I found a hole in the "pill" that the LED is mounted to and the XP-G R4 is on a smaller chip that barely covers that hole. That makes it harder to glue the LED in place but also greatly diminishes how fast heat can be transferred to the pill and then to the body of the light. This is very bad because even though the LED is very efficient, it produces more heat than light and if that heat has nowhere to go, the LED will cook in place and burn out.


So I looked around some more. On the Budget Light Forum, one guy is crazy about stainless steel flashlights and in particular loves the Aurora SH-034, a light that takes a CR123A battery. I have a light that takes a CR123A, but I feel like it is too small to get a good grip on, plus I don't want to worry about another battery size to keep in stock. A very similar light is the single AA Ultrafire C3, but the budget dealers change the designs of the lights without notice and lately they have been using lower quality parts. But then a new Aurora SH-035 was introduced that took a single AA and came with a pretty decent XP-E Q5, the same LED in the tiny flashlight. That LED is also in the same family as the XP-G I have so the reflector should be designed to work pretty well with my extra XP-G whereas reflectors for the XR-E that is in the C3 and SH-034 would not focus the beam as well. Not only that, but at $13.78, it was a couple of dollars cheaper than the smaller SH-034 ($17.08). I thought it might be a pricing error. So rather than wait for reviews of the light (which takes at least a few weeks after the light is introduced since it takes that long for them to be delivered from Hong Kong), I went ahead and ordered one.

It arrived a few weeks later, before any reviews were posted. I took the light out and played around with it. It seemed decent but had a few problems. There was a loose piece of shaved metal still connected to the threads in one place and there were only a few threads to hold the head onto the body of the light. Also the beam was a very tight spot of light. Generally that means the reflector is doing a good job of focusing the beam, but I wondered if the reflector wasn't actually blocking part of the beam. Anyway, a decent light on a AA battery. So then I tried a 3.6V 14500 lithium-ion battery which was supposed to work in the light. Last time I did this with a Uniquefire S10 that was not advertised to work with a 14500, I wound up burning up the driver and later converted the light to direct drive, bypassing the burnt out electronics and powering the LED directly from the positive and negative ends of a lithium ion battery. Although the SH-035 is advertised to work fine with a 14500, this time it worked much the same way. I got no light and a few minutes after opening the package the light was in, the light was dead. Even worse, when the driver fried, it created a dead short which effectively connected the positive end of the battery to the negative end, which means all the energy in the battery starts draining out as quickly as possible, which can cause the battery to explode or catch on fire. Yikes! I avoided catastrophe by removing the battery before that could happen. Then I wrote to DealExtreme where the light came from and told them the light was defective. I also put a comment on the product page that the light could fail on a 14500. However, a couple of other people at the forum also ordered the light and said it worked fine on a 14500, so I must have just gotten a bad one.

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Whether I got my money back or not, I wanted to try and fix the light. So I tried to get the driver out of the pill. A driver is usually held in place with a couple of blobs of solder, but once you remove those there is usually a notch where you can pry it out of its place. However this light didn't have any notches. But on the opposite side of the pill where the LED mounted are two holes where the positive and negative wires to the LED go down inside the pill. I tried poking through the hole with a stick and applying pressure to the board to pop it out. This wound up working, but the wires from the LED into the driver were very short so when I poked the driver out of place I also pulled so hard on the lead to the LED that it pulled the LED loose from the pill and then the wire pulled loose of the driver board. Now it was broken pretty good.

I looked for a possible short, but didn't see anything. Then I tried to put the LED back in place. It is critical to put the LED back in the exact center of the pill so that it lines up with the hold in the reflector when everything goes back together. An off-center LED will cause an ugly beam. And in this case, I glued the LED off-center and because the hole in the reflector was so tiny, I wound up shearing off the clear plastic dome over the LED. That is very bad. Whereas before the LED was still working and only the driver was dead, now the LED was dead too. To make things worse, I wound up messing up the rubber tailcap on another light, so I needed the 035's tailcap.

Fortunately DealExtreme did not ask me to return the light (though if I had been able to repair the light, I would have canceled my RMA, so it was kind of in their best interest that I tried to fix the light).

I had a new driver on the way from DealExtreme that I was going to use in a P60 drop-in and it turned out to be just my luck that SH-035 uses a standard 17mm driver just like a P60. And of course I still had my extra XP-G R4 LED looking for a home. So this seemed pretty obvious. I could put the driver and LED in there and get a new tailcap and have a decent light. Because I really didn't want to ruin my XP-G LED, I used a drill bit to make the hole in the reflector a little bigger and did a better job of centering the LED (it's still a little off). I put the driver in place and the light worked! But the driver was only for 14500 batteries and wouldn't work on the lower voltage of a AA battery. So I took a driver from a P60 drop-in (usually P60's are only used with lithium-ion batteries) and put that in there instead. At some point, DealExtreme gave me a refund for the $13.58, but I had paid $8.60 for the LED, $5.02 for the second driver (the first driver was only $3.19, but I found a good home for it), and a new rubber tailcap (which just arrived today) was $0.18 except that I had to buy 12 of them and only needed two (I didn't like the smooth black tailcap in my Ultrafire WF-502B), so realistically it cost me $1.05. The total damage was $14.67 to fix the $13.78 light.

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But this light rocks! The XP-G R4 is significantly brighter than the original XP-E Q5 and the neutral tint is much more natural-looking. The old driver was 5 modes, including SOS and a strobe, whereas I set the new driver to just two modes: High and Low, which is about all you need. The new black tailcap looks a lot better than the pale green glow-in-the-dark one the light originally came with.

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