The sought after AMC 7135 board master/slave sandwich mod - an explanation

I'm at work, so I can't see photos here. Maybe when I get home, but that's in the wee hours. Hopefully someone else will look in and say it's ok.

I think that at least ont of the 7135 chips has shifted during the desoldering. The one closest to the alligator clip has moved and the one farthest from the clip next to where the components are gone has also moved, (but looks ok). The one closest to the aligator clip does look like it might have moved too much to work correctly. I just can’t see for sure…

Can't see the other side to see if any of the four chips there have moved.

You got more moxy than me, I would never try this trick myself for this very reason. Every time I touch one of these tiny boards, something shifts that shouldn't and it dosen't work afterwards.

Hopefully someone else will come in and say their thoughts here.

As far as the removal, looks like you got the right ones off the board.

I can say for sure they never were touched and to my eye look the same , I’m more worried the left over solder and did I remove the correct ones?

I just doubly checked and those ones u referred to may have shifted look just like the untouched driver that I haven’t done yet , so maybe it will be ok , I’m in here now so gotta follow through ,lol

I could be wrong you know…

The rest of it looks fine to me.

Hm, you don't need to desolder anything to make that a slave board - it suffices to cut off just one pin (pin 3) of the µC. (That's the one above the "D" or "AD" in "L3AD4S")

Pictures r worth a thousand words , the lingo for most would not Be understood ? I was told u have to remove all4 pieces on the new kd drivers ,how do u cut them? Too small ,it was not too hard to heat up and pull at same time to remove?which ones are u saying to cut ?

Take that driver (or look at a photo),
locate the letters "L3AD4S" written on it,
it's the pin directly above the letters "AD".
(That's the third one counted from the little dent on the chip.)

Cut it with some fine cutting pliers - or something else.
(Damaging the neighbour pins won't be a problem.)

So the one I removed are wrong? Will the way I did it not work now?

You misunderstood me; it's ok to remove the µC completely, like you did.

But it's much more easy to just cut that one pin instead.

I love that extreme close-up. It appears that there is a trace link to both sides of the board above and a bit to the right of yellow pin #2 that connects the "pink" pins of the 7135 on both sides of the board together. I'm thinking that after soldering the led neg wire to each board you could solder a piece of resistor lead as a link to one of the boards in that hole and then stack them up, threading each board onto the wire and resoldering the link wire as you add each board. Heat sinking could be improved by potting each layer with Fujik, then AA a copper disk between each board with a hole for the link wire. Improved sinking might open up options for those wanting to mod older lights that have 6v lantern batteries. In general I use potting to help take the strain from wire links so that they don't break during testing and assembly. It also helps avoid other soldering problems. If this idea works it would make it easier to make a compact sandwich, even with the added copper.

Does anyone know if a reason this wouldn't work?

Scott

Just saw this thread and want to point out that in both Old-Lumens drawing and my original drawing above, there's one important thing missing... the ground wires that connect the slave boards to ground. Without those, LEDs 2 and 3 won't light. Here's the modified drawing:

Even better, here's a mod to the method above, whereby only the low current required to operate the micro controller goes through the switch, but not the high current for the LEDs. In this method, the regulators are operated by the mcu like a low current switch can be used to operate a FET or a solenoid switch. By doing this, the switch resistance is eliminated, thereby reducing parasitic resistance and increasing regulated runtime:

You can use any number of regulators and LEDs. The pic above shows 4-4, but 2-2 or 3-3 or even 5-5, 6-6, etc. would work the same way. Note that bypassing the switch to eliminate resistance is great for 3 cells or 4 weak cells, but I actually had to improve regulator heatsinking and add resistance back in when using 4 powerful cells and 4 tightly stacked regulators to avoid them overheating and throttling back.

I gave up because og 2 didn’t come on, now u have given me hope ,so I will give it another go tech junkie:) I didn’t do those grounds u have now showed :wink: Ty

Techjunkie is the bomb! He is King of all Ashperic XM-L Mag Mods!

I've said it many times-this recipe works great and I've used it on ~a dozen lights now. Next one I do I'll have to try the switch bypass; all of my lights were done before this came up... don't wanna tear my perfectly pimped lights apart now! Ideal as I have a few cut-downs that run on one 26650.

Rich

If you strip a bit of extra wire (1/4") from the switch-master ground wire for each board and use the hole located between the middle amc 7135 chips you can thread the slave boards onto this and the wire link I mentioned above to make a nice neat stack. A piece of cu or alu AA'd between each board to collect heat from the chips buried in the stack. I have some of these boards from illumination supply. I'll see if it works.

Scott

Do you mean like this?

Do you mean like this?

[/quote]

Here's mine for one of my triples:

I haven't used anything between the boards to heatsink but haven't had any problems either. Had to show off a little here!

Rich

Updated the first post with the new photos and information from TJ.

Exactly