ENEDED

I would take my multimeter and measure the resistance on U3 from the big pad to one of the three smaller pads. Compare the 2 drivers. I think you already did this. 4 and 6 million ohms is pretty much infinite resistance, so I donā€™t think that is a problem.

I think you can do the same thing for U4 measuring the pad on the left and bottom.

Iā€™m kind of guessing on this, though.

Um, itā€™s 4/6 miliOhms, not MegaOhms.

You sure? He used a capital M instead of a lowercase m. The miliOhms range is like a dead short.

I have a 3v 3 channel TA driver here. I tried to measure across the FET and got 1K ohm. Across ch 2 I get inconsistent readings. Across the single 7135 I got 4.5k 1k ohms. (Had to break our my new Probe Master test leads. DMM is still crap, though. Lol)

Oh you were talking about the resistors, not the RDSon of the FET.

IDK, Iā€™ll leave it to TA or someone who knows these drivers really well. He built it afterall. Lol

It is Mega. I conveniently call it Rdsoff. :blush:

Does your new FET able to fix the issue?

I donā€™t have suitable FET for it. I have only a replacement driver sent by Haikelite.
Before I install this new driver into the light, I wish to investigate how to repair the problematic driver.
Being busy at work that I canā€™t troubleshoot it yet.

I troubleshoot it and canā€™t find any fault on voltage. There is no voltage that can turn on U2 and U4. U1 has proper 5v power. There are difference below.
1.Voltage between LED+ and LED-
Problematic driver has 410mV while replacement driver has 320mV.
2.Resistance between LED- and ground
Problematic driver has 51Mohm while replacement driver has 68Mohm. I think my previous resistance measurement done a few days ago was wrong on decimal point.

Both drivers have similar current consumption, boot up with 6.8mA and then to 7.3mA and then to 56.5uA. This is without LED connected.

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 FETā€™s in at least a few of them, it was supposed to be corrected but no idea if it ever was.

The fake FETā€™s 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.

Ya, I agree the easiest way is to swap the FET. Too bad I donā€™t have any suitable FET at this moment.

Is this Vishay SiR164ADP suitable? FET

I used the SIR404DP and SIRA20DP - haven't seen the SIR164AP before. The SIRA20DP and Infineon are the 2 I use now.

That Rds spec looks high to me, compared to the A20. The A20 is pretty spectacular in specs.

For testing basically any FET with the same footprint would work.

Heck you could just remove the FET and see if the leakage stops, if so then it is a very high probability you found the problem.

A20 is indeed very low in Rds. Thanks for pointing out. Thanks Tom E.

I will try to get the FET removed then. Just need to get my friendā€™s help with his hot air. Thanks TA.

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. :person_facepalming: 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.

Sighā€¦wasting my hope and time.
Havenā€™t contact Haikelite yet, really troublesome to deal with Haikelite CS again.

So you didnā€™t 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 thatā€™s the problem since we would see all the new MT09R with glowing 70.2. It doesnā€™t hurt to try it, though.

If no change, maybe Haikelite is using some substandard FETs. You can buy some new ones from MTN E. They are really cheap. I bought 5 to have as spares. http://www.mtnelectronics.com/index.php?route=product/product&path=25_76&product_id=565

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.

The problem can come from two sources:

1. Leakage capacitance from the MOSFET. If the main lights are powered on, itā€™s not a big deal. On standby, and battery power, itā€™s a huge problem.

2. A secondary LED can do this too, although because itā€™s allowing too much current through, as JasonWW said.