Resistor mod for Meritline X8 Clone? (AKA Small Sun ZY-T614)

Flashlight Modding and DIY Parts
1

Hi,

I just got one of these from a Meritline deal:

http://www.meritline.com/showproduct.aspx?ProductID=78963&SEName=cree-t6-5-mode-white-led-flashlight#2

According to one of the reviews (from Tom E, I think), this is an X8 clone.

It seems like this should have a buck driver in it, and was wondering if anyone has tried a resistor mod on it?

There are a number of threads here, but all of the images seem not working anymore.

Thanks,
Jim

EDITED Subject to include Small Sun model name.

2

I went inside it and the layout is kinda wonky. No room for a trimpot and the way the toroid is linked in you would be unsoldering alot of ‘struts’ just to get the room to replace resistors. Just buy a buck driver from mtnelectronics, the 1/2-cell 3-amp one would pair nicely with this light.

3

Do you happen to know/remember what the driver diameter is (I haven’t had a chance to take it apart yet myself)? I have a bunch of the LM and CNQ 17mm buck drivers that do resistor mod (somewhat).

Thanks,
Jim

4

21.73mm, just right for the 21.5mm contact boards of Richard’s buck drivers.

5

Ok, thanks for that info, but ACK (!), I never seem to have the “right” parts :(…

I do also have some 20mm LM buck drivers that I can try, but those have components on the spring side, so probably are a no-go… but maybe if I combine one with one of those, or one of the 17mm buck drivers, with one of the FT 20mm partition boards that might work?

How “deep” is the pill? Do you remember?

Jim

6

@ Jim, its pretty deep, at least as deep as it is wide. There’s plenty of room. And a 20mm board won’t work, the shelf is pretty slim, a 20mm board might actually drop down into the pill, you need 21.5mm at least, or a 22mm board sanded down.

7

Here’re some pics of the driver from the light I got:

Notice that there is already an R180 stacked on top of another resistor (this is the STOCK driver):

The other side of the driver:

Is the already-stacked resistor the sense resistor? Can I stack maybe another resistor on top of that?

EDIT: Looks like the FET is a “40N03”…

EDIT 2: ON Semiconductor 67348, 1 datasheet pdf

45 AMPS, 25V?

8

@TGK,

Is the driver in the pics in the post above look like the one you had? Seems like the one I have might be resistor moddable if it’s just that already stacked one?

9

@ Ohaya

This is the driver that came in mine. And it was soldered into a brass pill.

10

Looks right to me.

11

Hi wight,

Thanks. I was going to ping you (you’re like “the buck driver guy” to me now :)!). The resistor is larger than the ones on the 17mm drivers I have, so I’ll have to hunt around for some. If not, would soldering the smaller resistor on top of the stack work?

Maybe another R200 (probably the closest I have to an R180) or an R100?

12

Don’t short the stacked resistor, mine blew the LED without even lighting up. Worked fine with 1 cell though before I hooked the tube back up :stuck_out_tongue:

13

I have 4 , 2 SMALL SUN , REF is about 35mm Deep ,and a large AL Pill. And a AL Retaining Ring holding Driver. ———— 2 SIPIK HK70 REF is 42 mm Deep, smaller Brass Pill , 22mm Driver Soldered to Pill.

14

Hi,

I’m not thinking of shorting the stack resistor. I think that would put the light into DD, i.e…, putting 8V across the emitter, which is probably what blew the LED up (might’ve been ok with an MT-G2, though :)!).

15

Yeah I need to go reflow a new LED onto a maxtoch board, but I think it will turn out good with some stacked resistors.

16

You’ve just described normal operation for a buck driver. Now you know!

You’re welcome. IMO you need to unstack the resistors to determine the current value. (Unless of course we know what the buck controller is, then we can make an assumption as to the current value of the ‘bottom’ resistor in the stack based on spec’ed sense voltage.) It’s probably QX9920 like so many of these, but I can’t see the markings on it in the picture.

The package for the sense resistors does not matter a lot, but it matters a little. Maybe it’s a 1212 package? Are they twice as wide as your 1206 and just as long? You just want to keep dissipation on each resistor in a reasonable range, but since they are stacked like that “a reasonable range” is probably a little lower than normal. I forget what they’re normally spec’ed at, maybe 0.5W each?

Also, I’m just curious, but what is the logo on the FET?

17

Hi Ohaya. That driver looks like it has the potential to push a lot of current due to the size of the inductor and large diode. I'm just going off their physical size (not looking at data sheets).

With so many unknowns, one has to guess what you would need to add to get to the current you want. You could just clip on an R200 and see what impact it has and then go from there. Otherwise, we need to know:

  • Current to the emitter on high
  • Value of the resistor under the top resistor

Or,

Voltage drop across the sense resistor bank when the light is on.

18

Hi,

The last pic in post #6 has the FET (upside down). If that isn’t clear enough, let me know.

Jim

19

Stock Tailcap current on high is ~1.06 amps. That’s with the current R180 stacked on top of some unknown resistor.

20