RMweb Gold Captain Kernow Posted January 22, 2020 RMweb Gold Share Posted January 22, 2020 I have some (self-adhesive) LED strips set up to illuminate my workbench. They are 12v, powered by a small plug-in transformer. Despite having checked all connections, they have recently started not coming on when I turn the mains switch on. They have eventually come on, but only after several minutes have passed. I don't know enough about how LEDs work but was wondering if this was symptomatic of a common fault? There is no problem with the mains supply, as other things work fine from the same plug. Many thanks. Link to post Share on other sites More sharing options...
Stentor Posted January 22, 2020 Share Posted January 22, 2020 I’m not an electrician myself but after a quick bit of Googling this seems to offer a general insight into what it might be and a checklist to work through: https://www.waveformlighting.com/home-residential/troubleshooting-led-strip-problems Clearly LEDs are not without issues, hope this helps. //Simon 1 Link to post Share on other sites More sharing options...
RMweb Premium MPR Posted January 22, 2020 RMweb Premium Share Posted January 22, 2020 (edited) Hi Tim, I would be inclined to start with the power supply - if you have a multimeter, disconnect the strip and probe the output and check the DC voltage at start up. When you have eliminated the power supply, reconnect the strip and probe the end of the strip. If you can access the solder pads, you should read close to 12V, even at the far end. If you directly access an led segment, you should expect to read a forward voltage of around 3V. Edit: my thought with the power supply is that there is an open circuit fault that clears as it heats up. Edited January 22, 2020 by MPR 2 1 Link to post Share on other sites More sharing options...
Il Grifone Posted January 22, 2020 Share Posted January 22, 2020 I would go for the power supply as I have never had a LED that is slow to come on. There is a first time for everything of course.... 3 1 Link to post Share on other sites More sharing options...
John ks Posted January 23, 2020 Share Posted January 23, 2020 I tend to agree with the previous 2 posts I assume your work bench is for working on trains & you should have a 12V supply for testing locos Connect the strip to that power supply & see how it behaves For those that don't know, these strips are usually groups of 3 LEDs & a resistor in series & these groups are in parallel along the length of the strip If a LED or resistor fail then only that group will not light & the rest of the strip will light If the power supply is at fault then the complete strip will misbehave John 3 Link to post Share on other sites More sharing options...
RMweb Gold Captain Kernow Posted February 13, 2020 Author RMweb Gold Share Posted February 13, 2020 Interestingly, what I have now established is that the longer you don't use the LED lighting, the longer it takes for it to come on. If I use the workbench every day, or nearly every day, then the lighting comes on as soon as it's turned on. If I don't use the workbench for a few days, then the lights have a delay coming on, but they do eventually come on. I don't know why this should be, though. Link to post Share on other sites More sharing options...
John ks Posted February 14, 2020 Share Posted February 14, 2020 I would tent to suspect the power supply things to try after a few days 1 try a different PS (power supply). if the LEDs light immediately then the PS is the most likely suspect or 2 connect a volt meter to the PS & LEDs & switch it on. If the volts rise slowly then the PS is suspect There's not much to fail in a LED strip, as I said a couple of posts back The following is speculation If the PS is at fault it could be a capacitor that loses its charge over a few days When it gets to a certain point it takes a while to recharge & turn on the PS John 1 Link to post Share on other sites More sharing options...
gordon s Posted February 14, 2020 Share Posted February 14, 2020 (edited) Not sure if yours are similar to our, but also check the small connectors to the strip. We have them under our kitchen cupboards and occasionally the connectors play up and exhibit similar problems. From memory I think I hard wired one of them to prevent the connector gradually moving apart. Edited February 14, 2020 by gordon s 1 Link to post Share on other sites More sharing options...
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