Help with McLux pr build trouble shoot,

[roguesw]

Hi guys, i have built the mclux pr, however, i think i might have shorted the converter board, i problem is i have no way of testing the light until it was fully assembled
i finished the build, pop the batteries in, when i pushed the kroll, it only lit up when the kroll was pushed in before it clicked into position, this was only momentary,
this happened twice and now the light wont go on again.
any ideas?
cheers
Des

 

[roguesw]

Hmm, been looking at it for a few mins now, i am thinking maybe the ground came into contact with the vin+
here is the detail of it, i put a blob of solder on the vi+ to contact the battery, but i think the solder point on the ground came into contact with the battery while in contact with the vin+, would this cause a short?
other than that i cant see how it could have shorted, also how can i test if the ls is dead or not?
cheers
Des

 

[roguesw]

Ok, LS is fine, just applied power to it and it lights up, guess i blew the converter, damnit /ubbthreads/images/graemlins/mad.gif

 

[Chop]

roguesw,
That's a nice conversation you're having with yourself there. /ubbthreads/images/graemlins/grin.gif

Yea, the converters that Wayne sells are very sensitive to shorts. I've always been concerned with this because I use Pila batts and the positive contact on the Pilas is wide. I usually use a button of solder on the + contact to aid in connection to the batt and I make sure not to put an excessive amount of solder on the V- of the board. I also use something to cover the - contact on the board like a thin piece of foam or rubber.

Sorry to hear about your misfortune.

BTW, you might also want to check the leads going to the LED. All it takes is one tiny stray strand of wire to cause a short and sometimes they're hard to see. On mods that I plan to build and leave alone, I tend to use solid wire rather than stranded to minimize the chance of stray strands.

 

[roguesw]

Yeah, you confirmed what i had suspected,
i followed Don's(McGizmo) advice on making sure that any of the solder points do not touch the E-Can, but forgot bout it touching the battery, i was planning on covering all the solder points with AA to make sure, now i know better. its gonna be a pita to remove the DB from the Ecan, its been potted with AA, luckily i am only out a converter board, not a LS, well, i am glad this happened in a way, learn from ur mistakes.
Thanks guys
Des

 

[McGizmo]

roguesw,

I just saw this post. Bummer! I feel your pain! Been there, done that and danged if it don't happen again on occasion! The DB is a great driver but in the E-can, there isn't a lot of margin for error. As chop suggested when using the Li-Ions, I think a good solder blob should be placed on the anode contact and then the perimeter of the PCB should have a thick coating of AA or some other material to isolate any of the LED leads or the ground via from the battery contact.

- Don

 

[roguesw]

Cheers Don,
This has been a really fast learning experience,
will take heed on advice for aa around the perimeter of pcb
i think i have the build process down better, i think i will tack the pcb to the ecan with a little superglue to hold the position, make sure nothing is in contact, then do a test to make sure things are working, then pot the inside of ecan and perimeter of pcb,
Thanks for the help Don and Chop, i really appreciate it.
Des

 

[tylerdurden]

Don,

when you suggest AA around the perimeter of the PCB, do you mean I should surround the battery contact with AA? or do you mean to coat the outer edge of the converter? If you could take some pictures at each step in the build process I would appreciate it, as the DownBoy seems to be a bit less forgiving than the badboy.

 

[Chop]

roguesw,
Just a thought. If you are using a permanent epoxy to pot the circuit (I hope I'm using the right term), you might just want to leave the sense resistors exposed, so that you can get to them.

As you gain more experience with working with circuit boards, you may decide to go in and re-bias later on. If you pot over the sense resistors, you won't be able to do this.

I actually potted a couple just using thermal compound in the hopes that I would be able to get back in there if I wanted to, but thermal compound is messy. Not unlike a baby's first number 2, the stuff just doesn't want to come off. I used to tend to just bury the circuit in potting compound, but I got the idea of potting around the sense resistors with AA from CM and I think that's a better way of doing it.

 

[CM]

roguesw,

Been there too (twice). I managed to short during a build one time, and the next time, I got everything working and after a few days later, decided I wanted to dork with the LED/reflector displacement. Got a strand of wire in between the anode and body and poof! I managed to get the epoxy off the e-can and converter and I'm going to attempt a repair. Would be nice if wayne sells the LT1618 separately but that would place additional un needed burden on him already. Advice: Once you get it working, DON'T DORK WITH IT /ubbthreads/images/graemlins/grin.gif

CM

 

[Chop]

CM,
Well where's the fun if you don't dork with it? It's funny that you say that because, everytime I've reopened a mod, I've managed to screw something up. What's even funnier is that I know I'm going to screw something up, but can't stop myself.

 

[McGizmo]

Tyler,

I mean surrounding the battery contact with a coat of AA. The solder blob will be an island surrounded by a shallow sea of AA. I think this step should only be needed or suggested in the case of using the Li-Ion cells with the large diameter + contacts. I would also make the solder blob tall. In general, I have been painting the via older nubs with nail polish to keep any errant metalic or conductive "lint" from getting in there and shorting out the PCB.

roguesw, I use super glue first in my assembly to bond he PCB to the E-can. I use the gel and with the head of a round tooth pick, I get a bead of gel around the inside of the E-can on the shoulder where the PCB will sit. I have a test LED with alligator clip leads that I clip to the LED lead wires and then power the driver (in the E-can) to make sure that the LED does in fact work but also to make sure that there isn't excessive current being drawn. With the DB's, I have found a couple times that one of the LED lead vias was contacting the rim of the E-can and a non fatal short was occurring. I am now in the habit of grinding away the E-can lip in the area of the LED lead vias if they are too close.

An important note on the BadBoy converter: There is a large "common" or ground via outside of the two smaller vias. I made a couple BB's that were dead; no current draw. In talking about this with Wayne Y, he mentined that he had just discovered that this large via is not connected to the ground plane but isolated! He said he would be putting up a cautionary note on his web page to NOT use this via.

- Don

 

[roguesw]

Hi Don,
good idea on the test LED, i have a spare(the one i pulled off the kl3) that i will use to test it (yup will heatsink that to a scrap of aluminium), have been looking at the ecan and i think just a few thou more clearance, i just removed it with a grinding tool.

Chop, hehe, i dont know enough bout electronics to play around with the sense resistor, i was having enough trouble figuring out anode and cathode believe or not.

CM, So when a short occurs, only the sense resistor is destroyed, so you could replace this and everything should be dandy?

Cheers
Des

 

[jtice]

I just made a quick page, to describe this problem with the DownBoy converters shorting out against the ecans.

I will post better pics in a few days, of an ecan with the notches.

Hope this helps alittle.
DownBoy Converter Technical Support Page.

 

[roguesw]

Cool Jtice /ubbthreads/images/graemlins/smile.gif

 

[CM]

roguesw,

When a short occurs, something in the path will fuse open and we know what an open circuit does to the BB's. It could be the sense resistor or the Schottky diode but either one will result in a blown converter. I've been thinking about protecting against shorts but it would not be fool proof since there are other things that can destroy the converter. Best rule I guess is to exercise caution and you can minimize the probability of damaging something. I should follow my own rules /ubbthreads/images/graemlins/grin.gif

CM