Müller Licht 5.5W/220-240V/50Hz/38mA/470lm/2700K/dimmable/E14 EB1500665 40036 (WHL #12)
Bit unusual item today – a plain E14 LED bulb that is sold in Germany, made by a German company, but I suspect it is made in China. Müller Licht has some stuff actually manufactured in Germany as well, but I don’t think this one was. But as it is not clearly indicated on the bulb and/or on the retail package (as far as I can see from product photos), I cannot say for sure.
Well, this was one of four identical bulbs that I bought for replacing halogen bulbs in my new home. I cost me 6.39€ a piece back then, shipping was free due to buying loads of other stuff and easily surpassing the free shipping limit at one of my favourite shops, voelkner.de. There are much cheaper ones of course, but the CRI of 90+ made the decision very easy for me. I am used to have good lighting and I will not go back to CRI 80 crap if there’s a chance to avoid that.
Why am I reviewing this piece for my blog, you ask? Well, I just omitted the date of purchase, which was the 4th of April 2016. Foreign readers need to know that in Germany, B2C shops have to provide a warranty (I wish there was a more exact word for that in English) to the customer for two years. If stuff fails during that period of time and it is not covered by a true warranty by the manufacturer, they have to provide replacement. Thing is: The burden of proof is on their side for six months only. After that, the customer has to prove that the item was faulty when he bought it, which is often next to impossible.
And, you may have guessed it… 04.04. plus shipping delay plus six months is just short of the end of October, when the bulb failed. Congratulations, perfect timing
So, let’s pull this sucker apart…
Outside has no visible screws, no nothing. Gripping the socket and turning it around yields some plastic shavings and the base falls off.
Two flimsy wires – don’t know if that was the reason to fail, one was still attached, the other was loose as soon as I saw it. The plastic dome on the top turns around, but needs some force to get off. I will keep that, looks like a very nice diffuser.
Next: The electronics are inside a metal foil (including lots of
tooth paste thermal grease), which is itself gunked to the plastic outer case of the bulb. Don’t know what’s the point in that, one could just make the heat sink a bit bigger? Had so saw the plastic open until I could fit a screwdriver. Breaking it free is easy and straight forward.
Still haven’t removed the LED board yet. It is secured by two tiny self tappers and the soldering joints are covered with some more silicone gunk. Easy to remove.
…and based on the amount of thermal grease, one could guess the failure mode: Big heat sink, bad thermal conduction to it. But the LEDs actually survived as tested on a lab power supply. These cannot be tested with my multimeters, as they have two LEDs inside the case in series, which means barely any light below 4.5V. The board is split across the middle, so there are 2x 7 LEDs in series, which is around 32V. That’s what the internal power supply would deliver. I couldn’t light up the entire board with my 30V supply, but only chains of six LEDs. As shown in the photo, the paralleled chains have no balancing resistor, so uneven current split is very likely. Still, as all LEDs light up (with noticeable differences in brightness at low current), the LED board isn’t the culprit.
Has to be the switching power supply then. It is wrapped as a whole in yellow isolation foil and then drowned in black potting gunk. Interesting technique, and close to impossible to take apart. The top has another isolation disc, and they even put a transistor on the outside of the foil to make better contact to…the ambient air. Well, something died in here.
Taking apart the accessible parts yields an orange 105°C cap, whose plastic wrapping is extremely brittle. This power supply must have gotten quite warm to make the plastic age that fast. On a funny side note, the font of the bottom part reminds me of the Team Orange…
…which is the fancy name of our local litter disposal service with the large orange garbage compactor trucks And that’s exactly where this Wan Hung Lo product will go to. I will however file a complaint to get this one replaced/refunded. I found out that the manufacturer has a 3 year warranty (not listed at voelkner) – but I will have to send that thing in on my own expenses and in usable form for error analysis. Too bad that’s not really worth the effort for a 6€ bulb that was fun to disassemble.