Müller Licht 5.5W/220-240V/50Hz/38mA/470lm/2700K/dimmable/E14 EB1500665 40036 (WHL #12F2)

Well, I guess I was onto something when I first complained about the failed E14 LED bulb back in WHL #12
Not only did the second one (out of four) die as shown in the followup #1, but now the third one is dead as well. And, which is my favourite part, the replacement for it was almost DOA as well. It blinks every few second and never fully turns on. What a heap of garbage!

So naturally I complained again ( :twisted: ) , and the guys from voelkner played the cheapest “shut up” card possible – they did a complete refund of the four initial light bulbs without any further questions asked. Well yeah that’ll shut me up money-wise, but I asked for more detail on the fault. And I put the Müller Licht service address on CC, but they didn’t respond at all. Great.
Still, voelkner told me to keep the garbage instead of returning it (on their expenses) and so I took it apart. I thought I’d salvage the sphere and throw the rest of it into the recycling bin, but I noticed they were different…

Sure, I’ve seen the different labelling before that, but I didn’t care much. It’s the same 400036 product ID that I’ve bought before, they just used a different labelling machine that uses some different font. Well, yeah, have a look at the opened unit:

They have respun the design!

The old LED board says “MK-2835-14K1-D” with date code 2014-5-19 (sorry for placing it upside down, I’ve refilled the missing electrons afterwards), while the new one says “MK-2835-14C-A” with date code 2015-9-21. Well, looks like I got old stock on my first order…

The board itself did not only change shape, but also mounting hole distance and LED placement. There are still 7 LEDs in series and two of these chains in parallel (no balancing resistor, no nothing). The LEDs have slightly different tint and I reckon they are a different type. While they still take 30mA at 5.50 volts, their low current performance is different: At 5mA, one needs 5.18V, the other 5.13V.

I also learned something from that board today. Obviously I’ve checked LED dimensions and they were 36mm by 30mm. Closest match you would find is the 3528 LED format, which is in agreement with the board labelling. But: These LEDs typically have a round emitter embedded in the square case. The ones here use much more of the 0.1cm² area of the case. So…turns out, there is a 2835 LED shape as well. Crazy! They use the same short side for contacts, but their emitting area (or that of the fluorescent converter material) is much larger. They are also usually specced for higher currents / light output, wider emitting angle and better color reproduction (remember these are said to be CRI 90+). Which also means their heat sinking must be better…but they are only half the height. Why not scrap the 3528 format and use 2835 instead?

Back to the LED bulb…after realizing the internal design respin, I also noticed the outer bulb case is not quite the same:

Obvious now, but who compares bulb shapes in the first place :lol:

So, it’s labelled the same 38mA@230V, 50Hz with 470lm at 2700K, dimmable, and of course E14 socket. And while the 400036 ID is the same, the internal number has changed from EB1501032 to EB1600281. I guess the first two digits are the finalization year of the design…so they need several months from PCB design to getting a basic LED lamp out? Or is it some batch identifier, as both of them are different to the EB1500665 of the initial blog post? Or maybe it’s the amount of thermal grease used in units of a millionth of a standard bee turd…they still didn’t cover the entire heat sink, but now it’s much better than before ;)

Anyway, I still miss one out of four lights in my living room because the replacement was dead, and I’m not sure if I should change the manufacturer entirely. After all, I have several more Müller LED products installed in the other rooms, and they are running under much worse conditions. They have higher wattage and are placed under good old incandescent glass covers, meaning much more thermal stress once they’re on. And for the bathroom, there’s also a high change in air humidity on a daily basis and much more on-off cycling. All of them still work well, only those under the best conditions fail prematurely. A bit like people nowadays ;)
Any suggestions? Must be high CRI, but I’m also open to replace the entire lamp housing for some fancy integrated LED goodness…

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