Filamented LED light bulbs — Would be nice if…


…they did work as expected.

I recently ordered 3 of these 4W LED light bulbs. They claim to have 470lm, or about 117lm/W, which is quite a good efficiency for cheap consumer-type LED bulbs.


Unfortunately only 1 out of 3 works.

The first offender has 2 dead filaments


The second offender is even worse, it has 2 filaments that do a little disco light show. Lots of random flickering. Bloody annoying!

Requested an RMA.


I thought it would be interesting to show the micro-structure of the COB assembly with the LEDs. I may attempt a tear-down later.



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4 Responses to Filamented LED light bulbs — Would be nice if…

  1. Barbudor says:

    Interesting. 1st time seeing those bulbs.
    Despite their defaults, they seems to be quite warm (most leds bulbs are too cold for me, even those labeled as warm). How would compare them to chinese warm bulbs ?
    Where did you got them from ?

    I hope you will be able to get them replaced.

    • robert says:

      I got these on amazon.

      The colour temperature is quite suitable for an incandescent replacement. I find it to be quite warm. However, if you take a look at the last image (recent update), you’ll see that some blue light escapes. This leads to visible banding. It appears that the phosphor coating is a bit on the thin side and allows blue light to escape sideways, maybe through the glass substrate.

  2. Barbudor says:

    Hi Rob

    I had also a look on ebay where you can find anything :) and I found not only such type of bulbs in various forms (thin, flame, …) but also bare “filament”.

    I try to find out how this is made. Apparently these are micro-leds placed around a substrate. As you pointed out, the colour comes from filtering. So they are not natively warm (but I think it’s true also for low-energy bulbs).
    I found also many French references that it could have been invented by a French manufacturer Girard-Sudron. Which let me skeptical …

  3. Levas says:

    I’ve bought severqal these lamps. Low power ones still working, 8 (9W) are all dead- it looks like overheating of diode strip. Also, I am now reverse engineering the driver- it looks it was “tuned” to max power and power was limited by drivers chip’s internal limiter for fet, not external shunt resistor…
    And “LED fillament”… it is chain, and if one diode is dead, all the chain is dead. And if there is some paralel LED strip, all the power goes to it… then it is overloaded and burns.

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