I've been really impressed by the brightness of the Light-for-me torch range and they look well made robust pieces of kit. But looks can be deceiving...
The early Light-for-me 4TEC RCA head with magnetic switch is a nightmare, the on-off switch is a rotating magnetic affair with such tight tolerances that use in salt water without disciplined washing after every dive leads to it seizing. This happened to a friend who in his strenuous attempts to unjam it actually managed to unscrew the cable from the back of the head!!! Small wonder they have now redesigned it to use piezo switches. Said head torch came my way for repair - my unlucky day!
Getting the head open is next to impossible. The (plastic) lens is held in place by a threaded aluminium ring with no key way. Presumably they have some cunning friction tool at the factory but no end of effort on my part could get anything to grip this sufficiently to get it to budge (even after 30 mins in the ultrasonic bath and heated to boiling point). In the end I had to drill a couple of holes into the ring and make a pin tool - that shifted it!
The (plastic) lens can then be extracted together with the o-ring by blowing a bit of compressed air into the cable gland entry.
Next out are the LED board, spacer and control PCB to leave the empty head.
Another 30 minutes in the ultrasonic cleaner and the switch collar still would not budge. Out with the gas pliers to give it a little persuasion. It moved! And another 10 minutes of faffing to get it moving (nearly) smoothly again.
Looking at the control PCB it was obvious where the wires from the umbilical had been attached before they were ripped off.
Another nasty surprise, the control PCB had a little circuit board blobbed on top of it (looks like a design cock-up correction). When the wires were forcibly pulled out they managed to rip this off the board (apart from one leg). So out with the micro soldering iron and the SMT gear to repair the broken tracks and resolder the bodge board.
Interesting to note that the markings of most of the chips had been ground off - brought back fond memories of some of the hobby kits in the 70's (that's the 1970's for you young people!)
The umbilical has four conductors which are divided into parallel pairs for + and -, these are then joined into single + / - wires going to the control board. The junction covered in heatshrink. Not pretty but what works works. The single wires were broken so I replaced these.
Checking the voltage from the battery pack - there was none (that's ZERO volts). Doesn't make sense so I had to unscrew the bottom of the battery pack (single o-ring) and behold a blown 3Amp car fuse. Found one in the spares draw and fitted it to check the polarity at the head end of the umbilical then removed it.
Now to re-assemble, should be easy right, oh no, not in any way easy. The umbilical wires go up through a central hole in the control board and sit in a small gap inside the spacer. But the wires from the control board to the LED board are so short that there is no access to solder the umbilical wires to the control board with the LED board in place. The two magnetic switches on the back of the control board have to precisely align with slots inside the head. It's like threading a needle wearing dry gloves.
I found the answer was to fit the cable gland threaded collar to the head but leave the cable loose. Then push the umbilical cable through the head, solder the wires to the control board and then withdraw the umbilical out of the head whilst aligning and inserting the control board, spacer and LED board into the head. With the electronics in place get the o-ring, (plastic) lens and aluminium ring back in place to hold it all together. Then slowly twist and push the umbilical wires back into place, locate the cable seal into the gland fitting and tighten the gland nut / strain relief. Oh, what joy to finally have the darned thing back in one piece.
Now properly tighten the aluminium ring.
Finally refit the fuse and test.
Return to happy owner.
Done! (Sorry the photos are a bit blurred)
L4M are nice bright torches, the 7TEC impressively so but the mag switch version IMO best avoided.
P.S. Did I mention the lens is plastic!