Question about Driver

Today arrived three 17mm AMC7135*8 Drivers from Kaidomain, so I started "modding" them.

One of those three was the donor, so I stripped three AMC7135 chips and got 1740mA to use with a R5. OK, VGood here, one driver working OK and three extra chips.

The other two drivers were intended for use with XM-L U2, one driver with 10*7135 (to get 3500mA) and the other with 9*7135 (to get 3150mA).

But the problem is that the one with 10 chips works at half current and the other with 9 chips pulls 2.7A.

I have always used a 5v 10A power source instead of batteries.

I cant remember exact values of the driver with 10x7135, and now it's installed on a flashlight so I only measured tailcap current (1950mA) and voltage (3.145v).

What is wrong? here I uploaded some pics of the driver with nine chips, showing how the extra chip is mounted. Is it OK?

Stacking 7135s is very difficult I have made at least 30 drivers with stacked chips and they very rarely work on the first try. If you are going to add only one extra chip stack it on the furthest one away from the ground wire. The bridge you made has never worked for me I don't know why. First thing is test your driver make sure it pulls 2.8 amps then add one chip to the furthest one from the ground wire, then test again make sure you still have modes and get 3.1 amps. Now either glue the chip with Fujik to the driver cover the whole chip smear the Fujik all over it or add another chip closest to the ground wire then test again. Those two spots are the easiest to get an iron onto. Try pulling on the chip above the solder points to make sure it is soldered good if it holds test it with a DMM to make sure you have continuity. This is a very difficult mod to do so don't get discouraged just take it apart and try again.

Thank you Erik for your help!

I thought stacking 7135s was easier! I Will try what you said, and then I'll come back to tell what happens.


Edit: Can you take a picture of one of your modded driver? Just to be sure of how to connect it and don't make a mistake.

Next time I make one I will take some pictures. I have an order coming in soon I hope. I seal them all up with Fujik before I do finally assembly so all you will see is a driver with a blob of Fujik stuck to it.

Not my images but this is what they should look like.

Thanks again Erik!

I tried again, like in the picture at the right and the result is... is (drum sound): Bad, pulls only 2,7A with or without a pair of extra 7135.

Maybe I'll try again with the other driver, because the driver which is now installed on the flashlight won't resist another disassemble again because one of the PCB conductors of the LED board is "unsticked", and also the driver can't be installed and uninstalled too many times.

Sometimes if you overheat the board when adding chips the 7135s on the other side of the board fall off due to gravity pulling on them when you loosen the solder from to much heat. That is why you should retest after you remove the added chips that didn't work and make sure you still have 2.8 amps because the chips you added may be working but the ones on the other side may not. That is just one of the many problems I have run into doing this mod.

I give up!

Five tries and still doesn't work following your steps even with brand new 7135's