The FET is supposed to be the SIR800 posted before, this is what I used in the drivers I hand made and have not heard of any issues with the 100+ that are floating around.
The production drivers though have used fake FETās in at least a few of them, it was supposed to be corrected but no idea if it ever was.
The fake FETās are most assuredly a problem and not up to the task of this light for extended use.
Without specialized equipment it can be very hard to test an FET properly. It is generally easier to just swap it out and see if that fixes the problem. This is the first thing I would try personally, for the $1-3 it would save a lot of time in the long run.
The other option is the small FET for the 1st channel could be an issue as well but far less likely since it sees a max ~0.5A.
I have taken out the FET with hot-air and solder the board back to the light with just LED+ and LED-, the leakage is not seen. It blinks two times when batteries make contact and then no visible leakage. I was happy for a short moment.
And then I put the replacement driver into the light by soldering all the five wires, the leakage is still there. Looks like replacement driver is not good either. Light function well, just it has this annoying light leakage during off.
Oh boy, not sure, but thought I seen someone post that some of the LED's may be the cause but I would think you would see it only that LED or LED(s), not all the LED's? Shame because I don't think I've seen this problem in my limited # of lights with this kind of driver and power.
So you didnāt have the switch wires connected at this point?
This reminds me of the time I modded my S70S and did a custom blue switch led powered from a positive source on the driver. I noticed the main xhp70 led was glowing faintly. It turned out that the switch led was allowing a bit too much current to flow through the driver. I then had to run the switch led power wire to a source before the main led. That fixed it.
Anyway, you might try disconnecting the switch led and see what happens. I kind of doubt thatās the problem since we would see all the new MT09R with glowing 70.2. It doesnāt hurt to try it, though.
If it works as it should with the main FET removed then that pretty much means the main FET is the issue. Simply get yourself a replacement FET and you should be good to go. There are a lot of options that will work just fine depending on your location. The SIR800 / SIR404 are good proven options and what I used in my drivers.
1. Leakage capacitance from the MOSFET. If the main lights are powered on, itās not a big deal. On standby, and battery power, itās a huge problem.
2. A secondary LED can do this too, although because itās allowing too much current through, as JasonWW said.
Thanks for all the input. I shall investigate further with your suggestions.
One thing puzzle me is why am I the only one encounter this issue for this light. I am thinking could it be my XHP70.2 leds are damaged a bit. When I initially used it with Sony 18650 which measured in 10m-20m ohm, could it damage the LEDs or change the LEDs characteristic?
I think next step is to unsolder the blue LED wire from SWLED pad. But months ago I have tried disable the blue LED during off, the light leakage was still there.
I seem to recall a couple other people having this issue. They might have had an MT09R, though. Both lights used the same exact driver (the Haikelite made Texas_Ace driver).
The original MT03 and MT09R have a blue and red back lit button (battery checker), whereas the TA variant has only one colour right? Hence the redundant wire.
I finally got my FET replaced with Vishay SIRA60DP just now. The printing on the FET is very sharp compared to the FET used by Haikelite. I highly suspect Haikelite uses fake FET.
It is not leaking faint light anymore. Will continue to monitor.
Light function well, just it has this annoying light leakage during off.
