LED downlighter repair

[Clive Arthur]

I have a flickering LED downlight in the kitchen. It's not the PSU, I've run it from a bench supply and it still flickers. It has a three position switch to change the colour temperature and the LED comprises a

17x20mm white board with two multiple chip LEDS, a central warm white and an outer ring of daylight. Te switch selects either or both. Only the warm white flickers, but this is the one we use. It's not the switch, I tried swapping the wires and there's no electronics in there.

This is a 30V 10W device, I could easily fix it if I could source the LED module, but I can's find a source - any ideas?

I don't want to replace the whole unit as there are others which it matches and I don't think the same model is available.

[ARW]

That's the downfall of LED.

It's f***ed so you have to bin it and replace the whole unit (in most cases).

[The Natural Philosopher]

I have found that LEDS like to flicker

Any or all of my kitchen ones will interact with each other even though they are on different dimmers.

When I had a desk light plugged into my bench and I was using a belt sander on an adjacent socket the LED would sometimes flicker when the belt sander was switched off.

The LEDS in my office here sometimes flicker on voltage surges too

Perhaps an RF choke in series?

LED technology is still work in progress

[Peter Able]

What's the make and model? Does it flicker when both LED strings are ON? Does varying the bench PSU slightly either side of 30v affect the flicker ?

PA

[The Natural Philosopher]

Well if its a bulb that ain't a lot...

I am beginning to think that the capacitor dropper type circuitry is extremely sensitive to RF and voltage spikes.

A few turns ow maind wire in a ferrite donut may help

[Steve Walker]

Yes. I am glad to say that the only LED unit we have is a single, flush mounted unit, so if it fails, I can replace it without worry about matching. The rest are fittings with GU10s, MR16s, E27s or BC22s, so easy to sort out.

[Theo]

If it's a branded unit, try the manufacturer. If it's not a branded unit, try fishing on Aliexpress.

Theo

[Brian Gaff (Sofa]

Not sure, the fact that all the leds in that cluster flicker so more like a connection issue. Are you saying that the bit that is faulty can in fact be removed on its own? If so then I bet somebody makes them, the snag of course is that they probably ship them only to the lamp makers in large quantities and probably in China. Brian

[Clive Arthur]

Yes, it's looking impossible to find one which will fit and have the same voltage, and I don't need dual colour, just warm white would do. The postage stamp sized COB LED can be removed - the whole thing seems to be quite well made, though there's no part number. Surprisingly the bezel is held on with four Neodymium magnets

The flickering is usually followed by a blackout after several minutes, even when connecting directly onto the LED. Dodgy bond wire, I suspect.

[The Natural Philosopher]

What is in a LED these days is not a given. There seem to be several different driver styles. The technology has been rushed to market on a wave of EcoBollox and its all still buggy as hell.

[Clive Arthur]

Well, I took the LED out for a closer look. It comprises two sets of LEDs, an outer ring of 'daylight' and an inner circle of 'warm white'. Each of these comprises 18 LEDs, and as it's rated at 30V that suggests that each set of LEDs is two parallel strings of 9 in series, and indeed you can see that with a magnifier.

So it's likely not a bond wire, though I've seen that failure in single LEDs before. It seems there may be some invisible thermal cut out - maybe a polyswitch type of device.

So I wired the LED up to the bench PSU again, and sure enough, flickering then extinguishing. I stuck it to an ally box with heatsink compound and hey Presto, it worked!

So I reassembled it with fresh heatsink compound and it's been on for an hour now. (In fact it's not heatsink compound, it's diamond grinding paste, but hey.)

So the moral of the story is, if your cheap-as-chips LED downlighter goes wrong, you can spend a couple of hours looking for a replacement and a couple of hours experimenting and fixing when you should be working at a fairly decent hourly rate.

Still, SWMBO is pleased, and that's all that matters.