sandall Posted December 10, 2017 Share Posted December 10, 2017 Does anyone have experience of fault-finding on cheap plastic quad-colour wash-lights? One of my small 5x quad-colours loses its red after a few minutes & only comes back (for another few minutes) after the light has been left unplugged for some time. For "Dear Red" read "Dead Red" !! Moderation: fixed Link to comment Share on other sites More sharing options...
graemeftv Posted December 10, 2017 Share Posted December 10, 2017 press each of the DEAD red led very hard when the rest of the red leds come on you have found the fault in the series. Very hot soldering iron reflowing the solder around that chip often solves the problem reminds me of old xmas fairy light days Graeme Link to comment Share on other sites More sharing options...
sandall Posted December 11, 2017 Author Share Posted December 11, 2017 I was rather hoping that a man with a natural multi-tone beard & a doll with a firework up her private parts might have taken one apart at some point. E2A: After a few days back in its box the red lasts for a few minutes, but after an overnight rest it's only about 40" - capacitor ?, or do these things have a battery ? Link to comment Share on other sites More sharing options...
timsabre Posted December 11, 2017 Share Posted December 11, 2017 I was rather hoping that a man with a natural multi-tone beard & a doll with a firework up her private parts might have taken one apart at some point.E2A: After a few days back in its box the red lasts for a few minutes, but after an overnight rest it's only about 40" - capacitor ?, or do these things have a battery ? Graeme's answer is most likely correct, it will be a bad LED joint or possibly a faulty LED, and you often can find it by poking/pressing the LEDs. If poking doesn't reveal the faulty LED, you can bridge out the red of each LED in turn and that will show you the faulty one. Sometimes the internal bond wires break causing intermittent operation, you have to replace the LED in this case. If it's just solder you will need a powerful soldering iron with a thick bit to reflow the solder Link to comment Share on other sites More sharing options...
sandall Posted December 11, 2017 Author Share Posted December 11, 2017 Thanks both. I tried resoldering, with no success, but then realised that the LED was just plugged into the 8-pin socket. A bit of wiggling with a fingernail & voila, it works. Link to comment Share on other sites More sharing options...
timsabre Posted December 12, 2017 Share Posted December 12, 2017 It isn't a socket, that's just how the led is built - a copy of the cree mc-e. You probably have a bad bond wire inside the led, if you want it to stay working you'll need to replace the led. Link to comment Share on other sites More sharing options...
alistermorton Posted December 12, 2017 Share Posted December 12, 2017 I'd expect the heat of the LED to move things over tie and the problem to recur. Link to comment Share on other sites More sharing options...
sandall Posted December 12, 2017 Author Share Posted December 12, 2017 I'd expect the heat of the LED to move things over tie and the problem to recur. You're probably right, but I left it on soak for about 6 hours, so fingers crossed. I don't want to get involved in trying to replace the led as it's a SMT chip, so not exactly a straightforward job without the right tools. Link to comment Share on other sites More sharing options...
timsabre Posted December 12, 2017 Share Posted December 12, 2017 You're probably right, but I left it on soak for about 6 hours, so fingers crossed. I don't want to get involved in trying to replace the led as it's a SMT chip, so not exactly a straightforward job without the right tools. They are not that bad to get off with a big soldering iron. Just get a big blob of molten solder across one side then lever that side up with a screwdriver. Repeat for other side. Remove excess solder and fit new. Link to comment Share on other sites More sharing options...
sandall Posted December 12, 2017 Author Share Posted December 12, 2017 They are not that bad to get off with a big soldering iron. Just get a big blob of molten solder across one side then lever that side up with a screwdriver. Repeat for other side. Remove excess solder and fit new. Next question - how to source the right one (the colours in a Cree MC-E are in a different order)? This one is a "4W" RGB+UV in a "Fun-Generation" 5x 4W light from a well-known German supplier, who doesn't supply components. Link to comment Share on other sites More sharing options...
timsabre Posted December 12, 2017 Share Posted December 12, 2017 Umm, difficult if you can't find a spare. If it's just one colour in one led, bridge it out with a link wire which will keep the rest working. Link to comment Share on other sites More sharing options...
sandall Posted December 12, 2017 Author Share Posted December 12, 2017 Yes, that's the fall-back idea, though presumably with a WW resistor to save overloading the rest of the chain, unless these things use constant-current drivers to feed the chains ? Link to comment Share on other sites More sharing options...
timsabre Posted December 12, 2017 Share Posted December 12, 2017 It'll almost certainly be constant current drive, should be no problem just to link with wire Link to comment Share on other sites More sharing options...
sandall Posted December 13, 2017 Author Share Posted December 13, 2017 OK, thanks, that'll be Plan B then. Maybe I should tack on a couple of wires, so I can do a quick fix if it dies on a gig. Link to comment Share on other sites More sharing options...
abbotsmike Posted December 13, 2017 Share Posted December 13, 2017 Could be a luxeon chip, or less likely a luminus device. Or something strange and Chinese! A dig round aliexpress and similar may help, or post the picture of the LED to the flashlight subreddit, someone on there may recognise it. I have a decent soldering station and am pretty comfortable with SMT work (and based in West London) if you do manage to source a replacement. Link to comment Share on other sites More sharing options...
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