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Kenmore 158: First Needle LED Failure

The first white LED fixture built to illuminate one of Mary’s Kenmore 158 sewing machines has been in regular use for the last four years:

Kenmore 158 Sewing Machine - mixed LED lighting

Kenmore 158 Sewing Machine – mixed LED lighting

We never found a good time to rip-and-replace the “prototype” with brighter SMD LEDs and one of the LEDs finally gave up.

They’re 10 mm white LEDs with five chips wired in parallel, which is obvious when you look into the remaining LED running at 1 mA:

10 mm white LED - chips

10 mm white LED – chips

The center chip is just dimmer than the others, which means their QC doesn’t tightly control the forward voltage spec.

The wire bonds on the anode terminal of the failed LED look a bit sketchy:

10 mm white LED - wire bonds

10 mm white LED – wire bonds

Fortunately, I hadn’t removed the 120 VAC wiring for the original bulb and I have two OEM bulbs from other machines, so I just removed my LED gimcrackery, installed a good old incandescent bulb, and she’s back to sewing with a pleasantly warm machine.

The fixture holding the LEDs broke apart as I extracted it, but it’ll never be used again:

10 mm white LED - fixture

10 mm white LED – fixture

The LEDs are rated at 3.5 V and 200 mA (!), but were reasonably bright in series from a 6 V unregulated supply. Perhaps a power glitch killed the poor thing? We’ll never know.

LEDs are reputed to have lifetimes in the multiple tens of thousands of hours, but I’ve seen plenty of failed automotive LEDs and fancy new LED streetlights out there, not to mention many dead and dying traffic signals. Seeing as how they’re in (presumably) well-engineered fixtures with good power supplies and are at most only a few years old, there shouldn’t be any failures yet.

 

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  1. #1 by captnmike on 2018-05-23 - 16:08

    Several things affect the life of LED bulbs, some of the ones that come to mind are how hard they are driven (drive harder and usually more light but less life) – getting rid of the heat and then plain old percentages, life expectancy looks like a bell curve of sorts –

    You might have driven them a bit hard in an enclosure that did not let the heat escape

    • #2 by Ed on 2018-05-23 - 16:42

      Nah, they lived in the stone-cold end of the sewing machine and ran maybe a volt under their rating. I didn’t measure the current, but it couldn’t possibly have been anywhere near their (alleged!) spec.

      Of course, if I bought my LEDs from reputable suppliers, as do all the automakers / DOT / municipalities with their failed LED lamps, then I’d have reason to kvetch … [grin]

  2. #3 by eriklscott on 2018-05-23 - 18:53

    A year-old streetlight has 3600 hours on it, give or take. But yeah, I know what you mean. New stuff is being designed so close to its limits it squeaks.

    • #4 by Ed on 2018-05-24 - 07:35

      Which should be maybe 10% of the claimed life, tops, so any failures in the year after installation mean something’s badly wrong. It’s not as if they’re dying like flies, but … they’re dying out there! [grin]

  3. #5 by RCPete on 2018-05-23 - 21:59

    LED tail lights seem to be getting better. OTOH, a lot of the early installations were on trucks, and I suspect had some sketchy sources for the LEDs. Similarly, traffic signals are getting more reliable, in a tough environment. (Winter down to -20F, with summer around 95F ambients.)

    The local city had red LED signal lights when we moved up in ’03, and San Jose had them in the late ’90s. It took a few years for green LEDs to make it on the scene; though SJ had them before we moved. Not sure when the yellows came in. Yellow turn arrows on signals are popular, so there might have been incentive to get them installed.

    FWIW, the early retrofits in San Jose included a bright flash when the signal went red. We think there was peaking circuitry for the incandescents to hit full brightness ASAO, and the peaking was left in place as the LEDs came on line. Took a couple of years to lose that feature. Got one’s attention.

    The electronic ballasts in my shoplights are hitting end of life. I got a 10 pack of 3700K Sunco tubes from Amazon, and beyond a few quirks, they went in all right. They’ll work with a (working) ballast, but do fine connected to the mains. Curiously, both pins on each end have to be tied together externally for the system to work. Might be a safety feature, I suppose. There’s a cryptic, but accurate connection diagram on the box.

    The first pack cost $90 a year ago. The reorder went up $10. Some outfit claims to offer a 6000K tube for about $80 in the 10 pack. (Not Sunco). I don’t think I could handle that much blue.

    • #6 by RCPete on 2018-05-23 - 22:03

      First order of tubes was in Feb ’17, and I just got the re-order. We’ll see how those work.

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