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Thomas sent me this dead light a while ago. It turned out to have an interesting bit of power supply circuitry that is a complete mind bender.
Thomas's channel can be found here:-
(He's taken a break from making videos recently while moving workshop.)
These lights are just landfill waiting to happen. A lot of materials that will be trashed because the manufacturers are designing them to fail to ensure ongoing revenue. It would be so easy to make them last over 10 times longer.
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I was digging through this stuff and found this light that was sent some time ago by thomas nadjie. I think this is probably the first time i've actually pronounced his name correctly. He's another youtuber, an electrician i'll, put a link to his channel down below, but this is a sylvania prominent brand, a canadian brand believe it or not, but this will almost certainly just be mass produced in china and he said this is one of many faulty products. We got, and this one in particular, is just flickering glowing dimly.

Sometimes it flickers up to full brightness and then goes out again, and this is the type of ceiling light that comes with this dome cover just the usual, what they might call a ceiling bulkhead. It's notable this one actually has a little silicone ceiling rail ring on it, which is quite neat. So let me show you what this thing is actually doing by turning the light off and then you'll see what it's actually up to. So when i turn the light off, you can see, the leds are just glowing dimly, they're, ramping up and down this one here in this area.

Here is notably looking a bit blue in the other suggesting it's got phosphor damage, so i'm going to bring the lights back watch your eyes. The light is back, let's explore. So this is a 12 watt fitting and that's kind of borne out by the power supply which says output is 150 milliamps at 80 volts max. This is a current limited supply.

It will be measuring the current going out and uh. It will have a range of voltage it can operate at so this is probably not just rated for the 12 watts. It may be used in lower power fixtures as well, but let's bring the kink calculator in and do some maths. So we've got 150 milliamps, which is 0.15 times the rated maximum output voltage of 80 volts equals 12 watts.

Okay, which is what this thing is rated at: uh sylvania cell circle, 12 watt, 800, lumen, worm white. So one of the differences between these uh professional landfill lights, because i've got a pet hate about these. This is the light fitting that when it goes wrong, you can't just take the cover off, because the cover does just paint it cap off and lifts off. You can't just go in and change a lamp with these you're going to have to remove the whole fitting.

That means that homeowners then have either choice and every time they would have just normally changed a lamp. They have to either call an electrician or they have to have a go themselves and that introduces the risk of electric shock. Now talk about electric shocks, this version has plastic covers you see all the ones kind of sold from prominent brands here. Have the little plastic cover to stop? You touching the leds, because the leds are reference to mains voltage, the ones that are imported directly from china via ebay and other sources? Quite often of this missing, it's just the bare leds, which has advantages, because the leds are often screwed to the back and provide better heat sinking.

But it does mean that if you had the cover off - and you were poking about inside the power on which is extremely silly anyway - then you could get a shock uh. This is also looking a bit brown here. Here's the next pet head. These things are designed to fail, they could under run them, they could have used double number of leds, they could have run those double number at half the power and they'd have lasted ages, but these things are designed to fail quite quickly and they do fail quite Quickly, part of that is down to bad heat sinking.

Part of it is just really grilling. These leds keep in mind this whole fitting is rated about 12 watts. I can see one two three, four, five, six, twelve 24 leds, so the leds being run about half watt each, which is quite a lot unless you get decent heat sinking. Is there decent heat sinking? No that telltale brown mark means this.

One has not been making good thermal contact with the back. If anything, a quick fix there might have been implying some sort of thermal paste or better still, that sort of you know that sort of spongy material - that's uh, used to come onto heatsinks the heatsink self-adhesive pads that could have worked, but there's another thing. We'll take a look at this power supply and we'll see if we can actually do something with this, but first of all, let's do a little hack. Let's see this led here is the one: that's grilled they're, all all the leds are in series so that one feeling has taken out the whole fitting i'm guessing.

It's that one uh. How can we test this? I can bridge that out one moment please, the soldier iron is up to temperature. I shall zoom down in this, so we can explore this repair together, so the led that was all baked crumbled off because it was baked. So, let's just bridge that out and bridging it out, don't do this with the power on uh in bridging it out.

All that's going to happen here is that uh well, there's no led there that the power is now going to be the same amount of current at 150 milliamps. But it's just going to be through slightly less leds. The power of the fitting would have gone down a bit, but we'll explore the power supply here and we'll see if it works uh if we can actually make that lower. If we were to want to do something like this, but the easiest fix here that these are not aluminium core pcbs, that's just an ordinary laminate.

The easiest fix is going to be to smear some compound by that, even that even literally siliconing it on with that thermal coupling glue to stick it on and then put it back in position would help, but as it is, let's just plug it in as it Is right now and see if that has fixed it or not, that has fixed. It is now back into normal operation right. So next thing now that i've unplugged it again, i feel i need to see i've unplugged it again. Let's disconnect the wires using a metal screwdriver do do.

As i said notice. I do as they say i don't recommend using a metal bodied screwdrivers for electric work, particularly wiring, that is still wired into the ceiling, so this uh that little blob of soda could have saved you. The cost of getting an electrician out or replacing the whole light. Fitting it could have got your light fitting running almost instantly but uh, because one led has failed.

You can see you can see in here that all the leds in that air have been grilled. It must have just not been pressing down properly onto the back plate. This is where the thermal coupling could actually save this. Another thing i've noticed here is that the uh, the white wire going from the power supply, is actually quite crushed here.

That's not good right! Please, let's get this driver off and we'll take a look inside the driver, landfill lights someday. Someone might i mean the eco hippies if they, instead of just banning the things that make electronics work, maybe they should actually get involved in banning things like this fittings that can easily be serviced. Do something useful, you know, that's me, being a isn't it. Yes, it is i'm having a grump, i'm being a total gen xer.

So can we get this cover off or is it good? No, that is coming off. Oh, it's looking unbaked inside! Well, that's nice right! Tell you what i'm going to take a picture of this circuit board and we'll explore the circuit board uh, which looks as though it's got filtering and stuff in it. It's quite neat, but we'll take a look at the circuit board and see if we can improve in any way if we can make a slight modification to it. That would make the leds last longer one moment please and resume some considerable time later, because this circuit contains a mind bender on the other side.

I'll show you in a moment it had me puzzling. I had to get the meter out. I also blew up another led, i'm not sure how much that but uh another one gave up the ghost it's another one that shows a dark skid mark in the back as well, so they've been grilled. Oh, you know what that was.

That's because this wire was trapped underneath and it was actually lifting this side of the case off. That's why that one's uh not been in fact they've. Neither of them at that each end have actually been heat sink very well, because they've been lifted up with this pinched wire, interesting stuff. Anyway.

What we have on the top of the circuit board is, we have the incoming supply goes through a fusible resistor, a con mode, suppression, choke, little filter, capacitor and an inductor there's a rectifier in the bottom, another photocapacitor and then an absolute mind. Bender of a smoothing circuit, then there's a inductor in this side that is pulsed by a buck regulator and then that charges up this capacitor which the leds are across and that provides the supply to the leds. So this is the top of the circuit board reversed. For convenience, because uh that way it correlates to what's underneath so here is the circuitry and i'm going to zoom down this a bit.

I think there's the uh fusible resist the other side, the commode suppression choke the photocapacitor inductor and then the bridge rectifier feeding over to these two capacitors with three diodes underneath them and i'll explain that in a moment, we've got a voltage divider based on three resistors. Here that's used for a voltage reference into the chip which uh detects against over voltage if the circuitry, if the leds go open circuit, i think it's for we've also got a little power supply for the chip coming from the positive rail which is via these two 300K resistors in series and a capacitor. It just provides a low current general power supply. For this we have the output to the uh circuitry, with a flyback diode here and a snubber across it, which is interesting, and then the capacitor for the leds uh and a 100k resistor across that to make sure that they don't glow dimly when the unit is Detecting site leakage current through switch wiring and also to make sure it goes out abruptly instead of fading down super slowly and then we've got a little filter, capacitor and two current sense.

Resistors later on, i shall chop one of these out and we'll see what happens to the power when i remove those. But let's look at the schematic, which is going to be lots of slices because wow it's a main bender. It is a super duper mine, bender. Here's the main bender bit, but let's start at the beginning, the mains comes in 240 volts in this case.

It goes through the fusible resistor 2.2 ohm through the commode suppression, choke, little filter, capacitor inductor and then the bridge rectifier and then the little third capacitor. On the other side, the reason for all these components that you wouldn't find in the cheapy imports is this is an attempt to try and filter out electrical noise to comply with regulations here, which the great imports don't do so normally on the output. Here you just expect one big electrolytic capacitor in that a bit not two uh with this matrix of diodes. So here's what happens initially when it powers up it will charge these capacitors up, but because these capacitors are effectively, if you can imagine conventional current flow flowing through the capacitor or charge capacitor up through this diode and charge this capacitor up, it puts the two capacitors In series and each one will charge up to half the peak mains voltage, which is about 170 volts, then, as the rectified output comes back down again, these will only start powering the rail when it reaches that 170 volts, because then each capacitor, this one will uh Discharge via this diode onto the rail, and this one will discharge via this diode onto the rail and what that means.

Is you end up with a really complex waveform which averages out because i measured it with a meter - that's probably not really suited to that. But 244 volts instead of the usual 340., and you might wonder why does it do this? I certainly did and then i works it out and did some tests and it was what i was thinking was power factor normally power factor the perfect power factor. Unity is when the current matches the voltage, so the current the current would be drawn across the full sine wave. The reason many of these led lamps have terrible power factor is because, when they're charging up the capacitor, it only happens at the top of the rectified sine wave.

So only draws it in the little bits up here, and that is kind of happening with this. But because, if you, this is a a rectified, ac sine wave, so you're actually seeing all the humps and above this zero volt level, it's charging the capacitor up to the capacitors in series up to 340 volts. But then the voltage across each one is 170 volts. So you end up with a sort of a sort of dc threshold here, so the voltage stays fairly high, but never quite dips down to zero, but never goes up.

It doesn't go smoothly up to the top. What this means is that the current is drawn over. Quite a significant portion of the same wave at the top, but you end up with very humpy noisy dc, but that circuitry doesn't really bother about that because it's stepping the voltage down anyway. So you end up with the current is drawn over a significant portion of the sine wave that we peak at the top as it charges these capacitors up it's very hard, but it ends up with the result is a 0.85 power factor which is actually very good.

It's normally 0.5 0.85 is really really good for these type of things. That is the only reason i can think they've done, that it's power factor, it's a mind. Bender. If you didn't get that, i don't blame you.

It took me quite a time to work it out. It was even hard just drawing the schematic, and then i suddenly realized that another schematic ages ago that i gave up on because i couldn't work out. What they were doing was doing the same thing. So here is the chip which i should have written the number on.

It is an empty 7812 one. Mt-7812. Actually, you know what i do have a data sheet for that uh and it kind of fits in the screen uh. It just shows the simplest form redirect for smoothing capacitor.

Interestingly, they've used the power supply to also one of the resistors to do double duty as part of voltage reference i'll cover that in a moment, and then it's very simple, now put us a standard buck regulator with a current sensor. Resistor. The circuitry is very similar to this, but it has a few extra frills. So here's the uh here's the power supply for a start, two 300k resistors and series to limit a very low current supply to the vcc pin, which is what powers the chip.

With respect to the zero volt rail - and that is a smoothing capacitor just for that, so that gives a very low current power supply. There's also a voltage divider here which sets what they call the over voltage protect, which i believe is to detect when something's gone wrong and the voltage across the leds, maybe they've gone open circuit. The voltage is going too high; it will actually shut the unit down and stop going above that just to protect things like the capacitor against damage, because the capacitor now puts on the rated 200 volts and they put it theoretically on that unit. Whereas the little cover is theoretically about 80 volts max the same um, so this is the bit: that's actually switch limiting the current via an inductor, the two millihenry inductor.

What happens? Is it switches down onto this rail here which has got two cent resistors? So it can measure the voltage across those to see how much current's flowing through that inductor when it turns on it, pulls it down to the zero volt rail, but because the inductor has no magnetic field. It has to build up, and initially it pushes back against, which limits the current, so that limits the current through leds, also charges this capacitor up for smoothing um when it senses that the it's reached a certain current threshold. The unit turns off and then the magnetic field collapses in the inductor, but because this end was being pulled negative and that end was positive now because it's collapsed in the opposite direction. This goes and goes positive.

This end goes negative and it finds its way through this flyback diode to the other end, so both when it's building up the magnetic field and when it's collapsing it's effectively charging that capacitor and powering the leds. Oddly, i thought this was going to be a short key diode, but it's not it's a standard, high speed, es1 j with a standard ford vulture about 0.6 volts, and it is a little snubber network across it, a 100 ohm resistor and a low valve capacitor. Just to clip any spikes to protect this diode, i wonder if that's because they were allowing for a short key there's the 100k resistor that just makes sure that that discharges quickly and the leds don't glow for a long time, and there is a low value capacitor. Just going to the zero volt rail just to provide a little extra layer of filtering and perhaps uh circuit stability.

So here's what i'm going to do, i'm going to plug this into the hobby and we're going to measure the power and then i'm going to chop. One of these off so the value of that resistance goes from well. What is that? It's a 1.35 ohms uh 2.7 ohms, two of them parallel so divide that by two is 1.35 ohms. So i'm going to double that, we'll see what happens, it may go bang! I don't think it will.

I think it will change the current uh, so let's zoom out and we'll bring the hoppy in and we'll look at this. I can't tell you how long it took me to work out that silly thing that weird triple diode double capacitor thing. That was just weird right. So let's bring the hoppy up and we'll stuff these wires, haphazard, linda here, which is a completely non-compliant way of connecting it's like the cliff quick test but dangerous, and i shall plug it in and the thing lights brightly and the hobby says: 11.6 watts, lovely power Factor: 0.85, great, so 11.6 watts right.

Tell you what i'll note that down notepad 11.6 watts? No, are we going to be able to have that? Does this thing go to charge? No! That's fine! Uh right where's that cinch resistor there's a cinch resistor down here! I'm going to lock one of them off right now, either just breaking one like that. That'll do that looks like it's mostly taking one out. Okay, now we'll see what the power changes to or if it just goes, bang because it doesn't like it, it might go bad. It's happened before uh plug it in the power has now gone down to 5.6 watts, so it is pretty much half the power.

It's gone down to yeah 5.6 watts, and that means that panel would last a lot longer with that resistor. But unfortunately it's not an easy hack. You literally have to take everything to bits. Get that circuit board out.

Look for those two current sense: resistors, always a low value like one or two ohms um, and then you have to remove one of them, one of the two in parallel, but that kind of worked and that fitting would last for ages. So lots of ways you could improve the life of this one is to put some sort of thermal compound in the back here too couple across another thing: you could sneakily do just one diode in each could just chop it off and put a bridge across. That would reduce the heat dissipation from the whole section, and this regulator would just regulate down the current to that it wouldn't be bothered by a slight uh reduction in the overall voltage across the leds um or you could just go the full thing and uh and Modify this or just put in a different one, rated for a lower power light so many things, but failing that, if it's blown up completely, you have the option of going to online and uh what they sell on ebay is retrofit power supplies and led modules with Magnets that you just physically stick it to the back plate with magnets and it's basically a circular circuit board with the magnetic supports and new insulation. So don't touch it, but it sticks over magnets and you either use the existing power supply or you use the power supply they supply with it, and some of them even have the built on linear current regulator.

That's going to get quite hot, so there's a there's options: it's not all instant landfill and hopefully soon they'll start clamping down and the creation of landfill like this, because it's such a waste. Oh here's! Another thing, that's worth mentioning! You want a bulkhead light, but you live in a mobile home or you want something that can power from 12 volts get one of these rip everything out, get 12 volt tape, uh and just put sections of 12 volt tape inside it. As many as you want for the power rating or multiple ratings colored, if you want and then you just run 12 volt supply into it and that's you got 12 volt light um, because it this uh these reflectors produce really good linear, uh illumination. I feel a need to prove that one moment please and an instant pronto bangerton style.

Here's some very badly installed led tape. Just a few sections: 12 volt tape, uh, you could use a diode or two and series if you wanted to make it more less likely to be damaged by this of charging voltage if you're using a vehicle, but i'd also recommend taking a bit of time short Sections avoiding and take putting it across so that it's not sitting above holes and things like that, because that's going to affect its heat dissipation, also laying in between i have here. But that's it. That's the three sections wired in uh parallel and i shall put the cover on and i shall turn the light off just to show you how even the elimination is so i'll, take the exposure off and turn the light off.

Oh that is excessively bright. Looking on the camera, but you know it is basically you're getting a good, even illumination over it, because these things are just very good. It looks great here for those three stripes. You can't see the stripes.

All you actually see here is this of the even illumination. So the light is coming back, watch your eyes, and that is it so uh. Thanks to thomas energy for sending uh this unit, it was actually quite interesting to explore it kind of it forced me to investigate the double capacitor triple diode thing and how it actually helps the power factor. It also reminded me just how crap some of these lights from even prominent brands are how some of them are no better than the grey imports from china, but there we go interesting stuff.

That is one of those little uh non-user serviceable. Well, not, except to us uh lights, that just seems to be flooding the market.

16 thoughts on “Fixing and hacking a light from thomas nagy”
  1. Avataaar/Circle Created with python_avatars Paul Amos says:

    Thank you for all the time you put into this reverse engineering, I am constantly amazed that so much thought goes into some areas then build it to fail quickly! As James S said high import levies on poor lasting tech would be the way to go, especially as so much policy is devoted to reducing our carbon footprint by 2035. But as you say we would need Government that puts the interest of the country and people above their own and I don't see that happening in my lifetime 😕

  2. Avataaar/Circle Created with python_avatars DC Allan says:

    Nice easy fix. Just a shame the LEDs fialed.

  3. Avataaar/Circle Created with python_avatars devttyUSB0 says:

    Very interesting cicruit. Thanks for the thorough reverse engineering of it! It is almost a shame they then just flop the LEDs on like that. This could have been a long lasting light!

  4. Avataaar/Circle Created with python_avatars No no says:

    The mind bending capacitor circuit looked a bit familiar to me, although turns out it was for a completely different application. I've seen them used for DIY programmers for Atmel/Arduino chips, which require "high" voltages (12 VDC I think) to change the values of internal fusable switches, to control things like chip speed, oscillator source, and response to brown out conditions. A variation of the diode and cap circuit can achieve, say, 12v out of a pulsed 5v source.

  5. Avataaar/Circle Created with python_avatars No no says:

    At first I was skeptical that the mind bending capacitor circuit is specifically to improve power factor, but if these are marketed towards commercial application, that would make some sense.

  6. Avataaar/Circle Created with python_avatars Fanta says:

    So it looks like the addition of a bit of thermal grease may have prevented that one led from burning out at a very minimum…. oh and also making a little hole for the wire to pass under the plastic too. handy to know.

  7. Avataaar/Circle Created with python_avatars Al Banana says:

    I've been burned a couple of times with landfill lamps. I now only buy lights with replaceable bulbs. The quality of the bulbs may be variable, but at least can be changed, rather than chucking the whole fitting.

  8. Avataaar/Circle Created with python_avatars TopEnd Spoonie says:

    Wow, that was awesome. I will have to watch this one a few times, just for all of the options.

  9. Avataaar/Circle Created with python_avatars Jim Hooke says:

    A few of the YT UK sparkies are using downlight fittings that take replaceable LED lamps so home owners can change their own bulbs and so on

  10. Avataaar/Circle Created with python_avatars Gregory Thomas says:

    Most of my lighting is 12VDC already…I run several battery systems…4 12Vbatteries along with 4 inverters to keep my all systems running.
    I use 4 Finder relays to keep the power on mains unless an outage occurs which turns off the relays an allows the inverters to keep everything powered off the batteries.
    Also use a couple 6V battery systems to keep my USB stuff powered as well…dropping the voltage with buck regulators down to the required 5VDC.
    So far I have made it through lots of outages and a few hurricanes as well.

  11. Avataaar/Circle Created with python_avatars Wim Widdershins says:

    An almost audible sigh of relief from the LEDs with the current drop.
    Manufacturers need to settle on a modular LED cob design, clip in replacements.

  12. Avataaar/Circle Created with python_avatars Iain Grant says:

    If you still need to tell people "I'm bringing the power back, watch your eyes" should they really be involved with electricity in the first place?

  13. Avataaar/Circle Created with python_avatars Henry Becker says:

    I remember Tom was unhappy that he had to replace a bunch of these fixtures that all failed around the same time, and that he was going to send one to you. Thank you for taking the time to dissect and explain. Always learn something watching your videos.

  14. Avataaar/Circle Created with python_avatars James S says:

    This is why I want to see central and local governments placing levies for these things based on their design lifetime and ease of repair. The shorter the lifespan the higher the levy. Change the rules of the game and watch the manufacturers start gaming it in new ways that align what we’re after.

  15. Avataaar/Circle Created with python_avatars AMDRADEONRUBY says:

    Nice a new video! You should make more fans videos. Interesting as ever

  16. Avataaar/Circle Created with python_avatars zh84 says:

    It's nice of the designers to address the issue of terrible power factors with LED lights.

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