LED bathroom light strip stopped working - how to replace?

Soldato
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22 Jan 2014
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Evening OcUK,

An LED lighting strip in my bathroom has recently stopped working. It's made of three cylindrical sections with LEDs within them, and these sections click into one another with a male end and female end. At the female end of one of these is a plugged-in cable. I have plugged each of these three individual sections into this cable, and none works, which to me suggests the issue likely lies with the supply to the cable?

However, the cable has been grouted and tiled in...so I headed into the loft and found the transformer that's connected to said cable, which is fed from a lighting chocbox thus:

Bathroom-LED-strip-transformer-labelled.png



Might I be able to leave the cable in the bathroom in place, cut the existing transformer out by cutting the cable from the transformer to the LEDs and disconnecting from the chocbox, buy a replacement transformer and transplant it in place by reconnecting the cut and disconnected wires?
 
I don't see why not. I'd think about getting a slightly higher rated power supply (12Vdc 1A) with maintenance free terminals for the wires and a unit that you can mount somewhere away from the insulation. The old unit may have overheated due to being baked in the insulation.

Do you have another 12V power supply that you could test the LED strips with?
 
I don't see why not. I'd think about getting a slightly higher rated power supply (12Vdc 1A) with maintenance free terminals for the wires and a unit that you can mount somewhere away from the insulation. The old unit may have overheated due to being baked in the insulation.
...

Very good point about the transformer being on the insulation - as you can see, it's quite the mess of wires, and the tiling and grouting in the cable to the LED strip...not sure how much thought went in when they put this in! Also good point about suitable terminal units, thank you.

Do you have another 12V power supply that you could test the LED strips with?

This is a problem - I do not, so I need to get one suitably rated, and then butcher it! I don't like the lack of troubleshooting with this, as you're quite right that the LEDs could also be busted for all I know. I do have a multimeter so are there any tests I can do to check out what may be surviving still from this whole assembly?
 
This is a problem - I do not, so I need to get one suitably rated, and then butcher it! I don't like the lack of troubleshooting with this, as you're quite right that the LEDs could also be busted for all I know. I do have a multimeter so are there any tests I can do to check out what may be surviving still from this whole assembly?

You wouldn't necessarily need to butcher it, i've bought universal transformers and they have a screw-block terminal (not sure on the technical name) attachment. That would save you from having to cut the end off just to join to your old wire.

You could measure volts/amps given off by your old transformer, i'm guessing you won't be able to find any contact points up in the loft though, so you'll probably have to cut into the wire anyway - which you'll need to do for replacing it.
 
well if confident check voltage at led end first and if theres a switch in the unit with the leds check that , then in the loft check 240v to transformer then if present check voltage out(incase wire broken in wall. ).
 
You wouldn't necessarily need to butcher it, i've bought universal transformers and they have a screw-block terminal (not sure on the technical name) attachment. That would save you from having to cut the end off just to join to your old wire.

You could measure volts/amps given off by your old transformer, i'm guessing you won't be able to find any contact points up in the loft though, so you'll probably have to cut into the wire anyway - which you'll need to do for replacing it.

well if confident check voltage at led end first and if theres a switch in the unit with the leds check that , then in the loft check 240v to transformer then if present check voltage out(incase wire broken in wall. ).

Thank you both. Checked with the multimeter and indeed it was the transformer.

All now sorted and working again with a higher rated transformer and connected up using lovely Wago connectors - they're very lovely things to use compared to the fiddly screw-in ones.

An interesting thing though: having turned off the lighting circuit at the fuse box, and checking the feed with the multimeter, it read 2.4V and 0.0A So I went back down and switched off the plug circuit too, now 1.9V then back again to switch off the cooker, now 1.4V...etc. etc. with each of the fuse box switches until everything was off, and finally it read 0V (actually 0.001V).

Was a voltage being induced into the lighting circuit by the other circuits?
 
An interesting thing though: having turned off the lighting circuit at the fuse box, and checking the feed with the multimeter, it read 2.4V and 0.0A So I went back down and switched off the plug circuit too, now 1.9V then back again to switch off the cooker, now 1.4V...etc. etc. with each of the fuse box switches until everything was off, and finally it read 0V (actually 0.001V).

Was a voltage being induced into the lighting circuit by the other circuits?
Likely. It's not uncommon to see a few volts on a cable from inductive capacitance or leakage I think.

Just to check - how did you measure current? Voltage can be checked in parallel/by placing your probe between any two points to read the potential difference between them. Current is by definition travelling along a wire so has to be read in series i.e. the meter must be inserted into the circuit by removing a wire and using the meter to bridge the gap. Unless you have a clamp meter for current?

Just asking in case you need to measure current in future - IMO I've never needed to with AC/house wiring :)
 
Likely. It's not uncommon to see a few volts on a cable from inductive capacitance or leakage I think.

Just to check - how did you measure current? Voltage can be checked in parallel/by placing your probe between any two points to read the potential difference between them. Current is by definition travelling along a wire so has to be read in series i.e. the meter must be inserted into the circuit by removing a wire and using the meter to bridge the gap. Unless you have a clamp meter for current?

Just asking in case you need to measure current in future - IMO I've never needed to with AC/house wiring :)

Thank you for checking these things - any guidance, advice, education of any sort is greatly appreciated. I opened up the choc box and holding both probes in one hand, inserted the negative probe into the neutral terminal and the positive probe into the live terminal. Did this for both voltage check and amp check, once I'd switched the probe ports. Was this correct?
 
Thank you for checking these things - any guidance, advice, education of any sort is greatly appreciated. I opened up the choc box and holding both probes in one hand, inserted the negative probe into the neutral terminal and the positive probe into the live terminal. Did this for both voltage check and amp check, once I'd switched the probe ports. Was this correct?
That works for reading voltage but won't for amps/current. Here's a diagram that might help explain how current is measured in series:

So it's easy to put probes anywhere for voltage, but measuring current is a bit more involved as you need to break the circuit to insert them. There are other meters available that clip around the wire if you're very keen to measure it frequently.
 
That works for reading voltage but won't for amps/current. Here's a diagram that might help explain how current is measured in series:

So it's easy to put probes anywhere for voltage, but measuring current is a bit more involved as you need to break the circuit to insert them. There are other meters available that clip around the wire if you're very keen to measure it frequently.

Thank you kindly! So I'd have to break the circuit and then be using the multimeter to reconnect? I can see why you've not done that on your house wiring!
It sounds like I'll never actually need to check anything other than voltage on the house wiring, so I'll just avoid even thinking about amps until I'm checking smaller electronics.

That being said, I'm liking the look of the clamp type! No needing to make contact or expose wiring etc...DIY maths is making me justify it as a useful tool for...checking...things...

Cheers again @LuckyBenski

Edit: Actually looking into them, I think they're rather more specific-use than I'd assumed given you can only check things with single wires, rather than e.g. cables to appliances. Makes sense when I actually put a tiny bit of thought into it.

I wish I'd learnt even basic electronics at school. At least it's keeping the sparks in trade!
 
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No worries, knowledge is power. Tools help :D This sort of thing is definitely stuff you can DIY. Common sense and a little knowledge of convention in UK homes goes a long way. A clamp meter would be nice but I've not quite needed one yet. I wouldn't hesitate to get one if it would make me safer when messing with 230V AC. My strategy is to turn as much off at the breaker as I can and test it's off with a meter, then crack on.

As far as current in appliances goes - I've got one of those 13A socket power meters. Brilliant for seeing how much devices use instantly or over time e.g. air conditioners which kick on and off as temperatures fluctuate. It's been used a whole lot more than I expected when I bought it!
 
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