Father's Day SRK

LED Flashlights – General Info 18650 Flashlights
1

Today is Father’s Day and I want to give the most important man in my life something related to this hobby that I also love. At the same time, I thought I would document one way to address the common issues that SRK’s have.

The SRK I got had more issues than normal and I did not have time to get a replacement. Here are some of the parts I used to fix them:

The wires to the LED’s are the same gauge that was used for the electronic switch. Replaced the LED wires with 18 gauge. I know it is overkill, but it’a the only suitable replacement I had on hand. Pill fit loose and is somewhat thin. So cut a copper sheet to put behind the pill. Thank you dochomak for hooking me up with the copper. There is a good size gap around the pill ledge. Since it is below the threads, the copper sheet is too small to reach the sides of the body. Pounded and filed a solid copper wire into shape to fill the void. Here it is part way through shaping:

Here is it in place. The anno has been sanded off the pill ledge to help heat transfer:

Here is the back of it:

The pill fits loose. Used alcohol to clean threads and put 2 layer of copper tape on the threads inside the body. The tape extends up a bit to help further transmit the heat to the body. Due to the larger diameter of the body above the threads, I had to split the tape every 1/2” or so to get it to reach the wall.

Driver was missing a FET and had resisters missing, extra, and out of place. Used six amc7135’s and set resisters for other 2 leds to 1.78 amps. Thank you relic38 for identifying the PWM pin on the MCU. Oddly, the 2 non-amc driven leds drop out first before the 2 amp (6 7135’s) led when battery voltage gets low. Maybe it’s not the MCU that cuts out the leds, but the FET’s that cut out a low voltages? Here is the driver after fixing:

To reduce resistance in the tail, I sanded the anno off the ledge that the tail board mounts to, copper taped the board, and copper braided the springs.

I know the copper tape looks wrinkled, but it is flat and well attached in the places that matter.

Copper taped the top of the pill. Copper tape is very soft and the pressure from the reflector should press the emitter bases into the copper. Used some thermal paste for the micro gaps.

The beam looks funny on these SRK’s. I stole the led insulators from my TR-3T6. Helped better center the emitters and smoothed out the hot spot nicely.

Well, I’m off to see my Dad. Happy Father’s Day everyone!

2

That’s very kind of you. I think the modded SRK shows your care and love more than any stock flashlight can.

3

Very nice mod. You lost me on the driver but thats not hard. Enjoy your fathers day.

4

You wasted your time with the electronic switch. It switches less than a milliamp of current. Wires smaller than a hair can handle that just fine.

5

I do feel the copper tape under emitters is more hinderance than help. The adhesive layer is an isolator but to what degree? Who knows….

I applaud your care in details on a gift for a very important man!

6

I waste my time on a lot of things, but criticizing others harshly in their father’s day threads is not one of them. I didn’t touch the electronic switch wires by the way. I replaced the emitter wires which were the same gauge as the electronic switch wires.

7

Yeah, I was concerned about the same. I think it is a benefit though. The adhesive seems to transmit heat and electricity very well, but I have not attempted to measure it. If it does insulate some, I think it is offset by the copper rapidly transmitting the heat over the whole pill. I did it to another SRK. Both that one and this warm up very rapidly to the touch.

Thank you for the input. It’s a valid concern. Someday, I will try to take measurements.

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Thank you ryansoh3, MRsDNF, and TrakTuned for your kind words.