Electronics > Repair

Snap-on LED Work Light Malfunction

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Xena E:
If it's running at temps hot enough to melt solder it wouldn't last long, if you tack it down you'll be able to feel how hot it gets, assuming it works again. It just looks like a shitty assembly job.

Smoky:
Yeah, the leg on the IC that doesn't have a pad underneath is clearly up off the deck as if the IC was never resting down tight on the pads to begin with. But the way those two pieces of solder look to have slid away from the legs of the IC seem odd.

Re-solder I will do :-+

floobydust:
Caution - the LED's are hazardous live, this power supply does not isolate mains so there is a shock hazard.
MT7873 Non-isolated LED CC Buck driver IC, it's got no thermal pad.

Usually with chinese LED fixtures I will remove one (of the two) current-sense resistors to reduce power output as everything runs super hot. R6, R7 0.33R in parallel I think, so I would remove one and 1/2 the power for long life and cooler operation- if you see fit.

Also I would inspect the LED's and look for the black dot of death inside, for ones that might be failing.

Xena E:

--- Quote from: floobydust on September 30, 2024, 07:27:29 pm ---
Usually with chinese LED fixtures I will remove one (of the two) current-sense resistors to reduce power output as everything runs super hot. R6, R7 0.33R in parallel I think, so I would remove one and 1/2 the power for long life and cooler operation- if you see fit.


--- End quote ---

Yes! good call. you can often reduce the current by half with very little reduction in apparent light output.


--- Quote from: Smoky on September 30, 2024, 07:00:53 pm ---Yeah, the leg on the IC that doesn't have a pad underneath is clearly up off the deck as if the IC was never resting down tight on the pads to begin with. But the way those two pieces of solder look to have slid away from the legs of the IC seem odd.

Re-solder I will do :-+

--- End quote ---

Can't hurt to try, nothing to lose: if it's faulty and got so hot as to desolder itself you'll soon find out, it'll do it again or just not work.

X

Smoky:
I cleaned up the solder joints that looked suspicious and left the others that look clean and smooth alone. I find messing with old lead-free solder a pain. I use the lead+silver type and it's an absolute pleasure to use. The crooked capacitor Gyro spoke about is actually soldered-in very well and no need to touch it. The original electrolytic capacitor was put back in too. The brown area under the legs on the left of the IC is not burnt, it's actually just exposed PCB:



I plugged the work light in and flicked the switch, and just like that, wham-o, I'm blind, I can't see!



FloobyDust, resistors R6 and R7 happen to be a combination of .33 and .68 Ohms to ground. So is it as simple as removing the .33 Ohm resistor to lower the intensity of the light to roughly 70% output?

Thank you :-+

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