I'm over today, multiple stacking 7135 fails

I’ve stacked plenty of 7135’s but today I can’t seem to do it. The drivers keep changing to single mode direct drive. My solder lines look clean but I’m guessing I’m shorting somewhere but where? Single sided 7135 1.4a boards with guppydrv.

Could be short inside a 7135 chip. They’re all parallel, so 1 short shorts them all. I’ve had the same problem a few times.

Check the current. If output equals the sum of the chips then Vcc(chip control pin)is shorted somewhere. If output is more than the sum of the chips then the short is from led- to ground somewhere(either on the board or the mcpcb usually the reflector) and you’re bypassing the chips.

I've been using these, when I have room. Much easier, but it does take a little room for them.

http://www.mtnelectronics.com/index.php?route=product/product&path=25_104&product_id=337&sort=p.price&order=ASC

http://www.mtnelectronics.com/index.php?route=product/product&path=25_104&product_id=341&sort=p.price&order=ASC

It’s the ground shorted the the LED- somewhere on the driver, just gotta figure out where.

Center pins are also ground or it could be a strand of solder from led- pad to gnd ring. I sometimes clip off the center pins and just use the outer ground tabs instead. Often times the center pin pads aren’t even connected with a trace to the outer ring anyway.

I soldered the ground on the back side of the 7135’s, but I didn’t clip the center leg. I’ve done that in the past. Looking at the picture below, which I assume will be similar to the single sided boards as well, the only place I could have screwed up is somewhere the negative and ground are shorted on the front of the 7135. I’ll have to go back and double check. I’ll probably just desolder all the 7135’s if I can’t find the culprit and clip the center leg. That’s what I get for taking a shortcut, but I was trying to save time since I’m soldering 16x 7135’s to each driver! Shortcuts are now costing me more time.

Good luck. It’s a pain when a driver doesn’t spec.

Well, I am about to start all over. I just took the 7135’s off both and checked them all. It’s a good thing too. I must have had a short on one. Never could really see it but it’s working now. The other actually had a bad 7135. I don’t know it it got over heated, or messed up bending the legs, or if it was bad from the factory. On a side note, I didn’t realize the variance between the 7135’s. They ranged from .372 to .382.

I have a feeling (=not tested) that there's more junk 7135's around that do not do their job properly than a few years ago: current is noticably sensitive to input voltage, or they just fail.

Well now I will make a habit of checking them before installing them. On the board that all the 7135’s checked out ok, I can only assume it was my screw up.