Bought 10pc of BLF X6 drivers on sale. The first 3 I tried (so far the only 3) start to smoke from the solder pad for the diode (diode, right?) that is circled. They get very hot to the touch and start to smoke within about 2 seconds. This happened while bench testing them before installation as I always do.
Other than the fact that the magic smoke may be permanently gone (?), what could smoke here mean?
A second question: what is the significance of the positive wire solder bridged to the nearby capacitor? On my x6 drivers and the x6 picture I Google Image searched, it is solder bridged. Bit I noticed on other GPS results for the A6 driver, it was not. (as seen below).
British car manufacturers had this problem for a long time with their electrics, and now stock the necessary parts for fixing it, perhaps they are compatible?
The load on the first driver was a Luminous SST-40. The second driver was tested using a multimeter across the LED wires, the third driver had power connected without any load and still did the same thing.
For the first driver (which I assumed was good), I wired up the driver and LED into the pill and then tested it using a little DC power supply that I have set to 3.0V and 0.05A. I use it to do quick tests of LED reflows and driver solderings, just to check function with a very small voltage/current. When I did a brief touch connection using that power, I got light from the LED so it passed that “test”.
But when I finished the assembly of that flashlight, the modes were behaving very strange. So I disassembled the light and did some quick troubleshooting to confirm no shorts or bad solder joints. Then I applied 3.7V from an 18650 in a holder and that is when I saw the smoke for the first time. I thought MAYBE there was a 1% change I had applied reverse polarity at some point, so I started testing bare drivers from the same batch.
Driver #2 was tested with the 3.7v 18650 and a multimeter across the LED wires. Smoke from green circled diode pad.
Driver #3 was tested with the 3.7v 18650 and no connection across the LED wires. Smoke from green circled diode pad.
I will get some pics tonight when I get home from work. I took a look at the driver and didn’t see any obvious issues, but I’m fairly ignorant when it comes to PCB design/layout and component choice, so my inspection is not foolproof.
Considering that 3 of 3 (100% so far) drivers from this order of 10 have had the same issue, I wondered if it might be a known issue somewhere. With an easy fix, too, right? I can dream… :person_facepalming:
Is hard to believe that all 3 drivers are defective (DOA) !!!...Looking at the original pictures and comparing with the ones you took ( BTW , very nice ones !...) , I noticed a difference . Your' drivers has a bleeding resistor ( 471) , from + LED to GND .In a "normal" driver this resistor should not be there , unless is used for an illuminated tail switch. I'd suggest you to do the following :
Remove the 471 resistor .
Check if the S4 schottky diode is good ( this one is feeding the MCU Atmel with + V) . If not , replace it with any Schottky diode that fit in the space.
Check if you have continuity between spring ( +V) and the anode of S4 ( should be ).
Check with your instrument , set on "resistor" :
1 . Resistance between spring (+V) and outer ring (-V , GND) should be in the range of Kohms or teens of Kohms .
2. Resistance between Kathode of S4 and GND , should be in the same range. Low resistance on this path means that the MCU is defective.
If everything is o.k. , with the 471 resistor removed , wire it up again and see...Good luck !
In that case, a follow up question: for the 3 drivers that I applied power, are they likely toast? (Dead?) Or would they probably be OK if I swapped around the MCU? Or could it just go either way?
I said above that I don’t know much about PCB and SMD design and layout, but I do know a bit about manufacturing them, including the equipment that feeds and places and inspects SMD for reflowing automatically. I can barely believe it is even possible to have that happen in this day and age.
Yeah the Attinies are pretty tough but I wouldn’t want to use them any more. If you contact Banggood and send pictures they will probably send new drivers without requesting to send back the wrong ones. If their complete batch is wrong it might take a while though …
I do not think that will be good enough. I think you will need a load, either led or maybe a resistor? Resistor would have to mimic led draw and dissipate enough heat.
