KD 3A Buck driver is malfunctioning

Please see this video.

http://www.youtube.com/watch?v=du3HDv3e5A8

Sorry the video is so short, I took it with my phone and I can only send videos if they are a certain length.



Anyway, I bought five of these drivers because the max input is 15 volts, and for ~$12 its a good deal. I usually use CPF member Download's 7135 driver's for most of my Maglite upgrades, but they only have a max voltage input of only 6 volts, and I need some drivers that can handle >6v for my customers with 5D and 6D Maglites.

So this is the first time I used this driver (even though I bought five of them). And I installed it into a 6D Maglite running six D cell alkalines.; about ~9 volts. So I made the correct soldering contacts between the driver, P7, and the Mag switch. So I fired it up to test out the new driver. I began cycling though modes, thats when I noticed when it is on high mode it will strobe for a second then switch to the low mode. Then a few seconds later switch back to high mode, then strobe and go to low etc... Afterwards I mounted the heatsink in the Maglite shaft to see if that would fix the issue; it didn't

What is causing this to malfunction? does the driver need to be heat sinked?

These drivers definitely need to be heat sinked. I am not sure if that is what is causing this particular malfunction.

Normally the malfunction works like this. Turn it on high it will run about 1 min or less and kick to low because it over heats. If you sink both the top and bottom that will fix this problem. If you sink the one you have installed and nothing changes, I would try another driver.

I tried a different driver and experienced the same problem. How exactly would I heatsink both sides of the driver?

OK, well I globbed about 1/3 of a tube of Arctic alumina epoxy on the back of the heatsink and planted the KD buck driver onto it flat side down. Then I taped it so it could dry.

What I did is took some aluminum flat bar and cut off 2 squares, I think they were 3/4" wide, but I dont recall for sure.

Then toward the edge of one of them I drilled a hole for the round black coil to fit through so the other components could be sinked to the driver. For the bottom I drilled on hole in the center for the batt + wire to fit through, and all the other wires I ran out the sides. Use a thin layer of your AA or ASE to stick the sinks to the board.

EDIT: since you already have the bottom stuck to the heatsink of your led maybe just add the piece to the top.

If this is the same age old problem these drivers have had this will give you much more runtime before the temp sensor kick in.

Good luck with your light. Once you get the bug worked out of these drivers they are actually decent.

Yeah I used a less precise globbing approach. The flat side is kinda flat and when pressed onto the back of the heatsink; it is slightly tilted so only about half of the back of the driver is thermally mounted to the heatsink. If it continues to over heat I'll squirt some Arctic Silver between the lifted side of the driver and the heatsink to get a larger thermal conductive area.

UPDATE: That didn't do anything! My driver is thermally mounted to my heatsink and is still mode hopping. And I just used like 1/3 of all my arctic alumina. Is there a better way of thermally managing this? Its already attached to the heatsink on one side.

Hmm, I have that same driver in my 2D Mag and it works just fine. I milled a pocket into the heatsink for the driver to sit in and only the edges touch the board.



I've run it for half an hour to see how hot it gets with no problems whatsoever. I did not install that pink gooey sponge thing that came with the driver (I think it's supposed to be used to help with the heatsinking or am I wrong on this?) nor any AA except to glue down the star to the heatsink. I'm using a C-bin P7 and two 18650 Li-Ion cells to power it through the stock Mag switch. It does sound like the driver board is overheating, though I've never experienced it with mine. Are the P7 contacts wired in parallel or series? My star-mounted P7 is wired in parallel. HTH.

I don't have access to a lathe so I cant do any of these custom heatsink jobs like you did. I just have some AA epoxy and H22A's heatsink. I don't know how else to solve this except for maybe globbing even more AA from the edges of the driver do the heatsink. Also, i did receive some of those soft pink things, they where for heatsinking purposes? I wish I had know, I think I might have thrown those out.

SmurfTacular said:

UPDATE: That didn't do anything! My driver is thermally mounted to my heatsink and is still mode hopping. And I just used like 1/3 of all my arctic alumina. Is there a better way of thermally managing this? Its already attached to the heatsink on one side.

Click to expand...

UPDATE: No you dont have a thermally mounted driver.

Ok seriously though. I am not trying be be insulting or rude ( I just couldn't resist the stab) but that glop of 1/4" thick glop of AA is doing nothing for you. Nothing...

In order to get any sinking at all you have to treat it like you would an LED. The wires will have to be placed in a way that allows the components to sit flat on metal with as THIN layer of epoxy.

I am not 100% sure that you are having the same issue as the rest of us with this driver, but I am sure that you will have to take some time and do this right in order to find out. Again please dont be offended, I am not putting you down or saying anything bad, I just want to be clear about how sinking a driver works.

SmurfTacular said:

I don't have access to a lathe so I cant do any of these custom heatsink jobs like you did. I just have some AA epoxy and H22A's heatsink. I don't know how else to solve this except for maybe globbing even more AA from the edges of the driver do the heatsink. Also, i did receive some of those soft pink things, they where for heatsinking purposes? I wish I had know, I think I might have thrown those out.

Click to expand...

You don't have to use a lathe. I think what PCC was trying to point out is that with the driver sinked to the bottom of his led heat sink he has no issues with his.

Where you put the driver on the bottom of your heatsink is a good place, and you don't need any special tools to do what I said about putting a piece of aluminum on the other side, just a hack saw and a drill.

I know how incredibly frustrating this can be, especially when by all rights you should have a working light and its only because of the product you received that its not. You will get it worked out.


If you turn the light on low or medium mode does the light stay in that mode or does it cycle through modes then too?

I thought having a thermal path toward the heatsink would be better than leaving it un heatsink'd. And FYI, I soldered all the wires on one side of the driver, leaving the other side flat-ish.
Well at this point I have run out of resources and options. What type of aluminum do you recommend using as a driver heatsink?

I have made ~20 P7 Maglites and I have the routine down. But I have never had to heatsink the driver, so this is all new to me.

SmurfTacular said:

I thought having a thermal path toward the heatsink would be better than leaving it un heatsink'd.

Click to expand...

You are correct it may be enough by its self. What makes me thing that you don't have a thermal path is this.

SmurfTacular said:

it is slightly tilted so only about half of the back of the driver is thermally mounted to the heatsink.

Click to expand...

To me it doesn't sound like much if any heat is being transferred.

SmurfTacular said:

And FYI, I soldered all the wires on one side of the driver, leaving the other side flat-ish.
Well at this point I have run out of resources and options. What type of aluminum do you recommend using as a driver heatsink?

Click to expand...

I just went to Lowes and got some 1/8" thick by 3/4" wide flat bar and cut a couple of pieces off that.

SmurfTacular said:

I have made ~20 P7 Maglites and I have the routine down. But I have never had to heatsink the driver, so this is all new to me.

Click to expand...

There are some other possibilities still as to what could be causing this issue. Heat sinking is a good place to start with these since they need to be sinked anyway.

When you turn the light on if it is on low or medium does it still cycle through modes by itself or will it stay in that mode?

It will be on hi, then strobe, then go to low and stay there for a few seconds, then go back to hi.I wish I could take some good pictures, my phone/camera cant focus on anything within a couple of feet away.

Unfortunately these drivers just suck hard for some , and work for others , all the ones I tried just sucked ...

Deal extreme has a driver [ 8.4v ] and if you go 9v then it might work for you , as for me I run around 12v through mine and it still works fine , been a while now and it has not died .
Im using the single mode version , but there is a 5 mode , which I have , but havent used as yet .

Its either that , or shell out $50+ for a better driver .

What do ya know! I already have that driver. I bought it for my first build and never used it. I guess now is the time to use it.

does every one of 5 drivers you bought do this????

The reason I asked about the mode changing in low and med is because it sounds like you have more than one issue. These drivers do need to be heat sinked, but you probly have one of two other problems.

One is a poor connection. If there is, and you are confident all the solder joints are good, then it may be in the switch. I have had this happen before. You could try hooking the circuit up without the switch and see if mode changing still occurs. Even the tiniest interruption in the current flow can cause these drivers to change modes. If the problme continiued, and it was my stuff I would try at least one more, and if it still happened then another. I buy extra of everything for this reason.

alpg88 said:

does every one of 5 drivers you bought do this????

Click to expand...

Haven't tried all of them, but two of them do.

vestureofblood said:

I buy extra of everything for this reason.

Click to expand...

thats why I bought five!!!

Im going to try that $5 DX driver.

UPDATE:

That DX driver is a miracle , everything works perfectly

Fantastic!!:twothumbs. I am glad you found a timely solution. Perhaps you can still return the other drivers. Either way it looks like you will have one more satisfied customer. Nice job.