Teardown: A failed SUNeCON S-SP/38 38W CFL Globe

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SUNeCON is not a brand that’s often heard around here, and for good reason. This particular CFL is a very special globe – at least to me anyway. I was walking through a “$10” shop in Hong Kong back in 2006 when my eyes were fixated on their lighting section. Aside from the Sunshine T5 fluoro battens I bought home, this was the other lighting related product that made the journey in the checked luggage.

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The main reason I bought this, was because it was the highest power rating CFL I had seen at the time with a bayonet cap base that would plug into most of our fittings at home. Locally, in Australia, seeing CFLs of over 20w was a rarity, and any over 26w was almost impossible except for the occasional variety-shop item at a significant premium. As I recalled, in the shop in Hong Kong, this was treated as a normal item, and priced significantly cheaper. It also had a spiral tube, which reduced the size compared to other multi-U based high-powered CFLs intended for high-bay applications.

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Of course, with the advent of eBay and online shopping, sourcing such globes is no longer a difficulty, although finding quality globes which are safe and do not emit EMI may still be an issue. Regardless, I was totally intrigued at the possibility of squeezing the same amount of light as you would get from a 1.2m 36w fluoro tube into something that could fit in a standard fixture.

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This globe had been part of our daily habits, and provided illumination for the main living area, around 5 hours a day. Assuming it did about 4 hours a day for 10 years, it still exceeded its 8,000 hour lifetime by running a total of 14,600 hours. It definitely did well, even if the light output did diminish somewhat towards the end.

Its failure was silent, without warning or sound, a few flickers and then it was out and never to relight.

Teardown

This globe was annoying to take apart because the plastic had become so brittle over time that it was impossible to pry apart. Instead, a hot knife was needed to cut along the seam and break the base apart.

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It was to no surprise to me that the wires inside from the primary were as thin as could be, and the PCB seemed to fit poorly with a lot of empty space surrounding it. This is the kind of “quality” we expect from an unknown Chinese brand. However, a closer look seems to show that it did survive a very harsh long-term torture.

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This was a green sheet of cardboard which is common in Chinese electronics, placed underneath the PCB as additional insulation against the globe electrode wires. It has been exposed to heat for so long that the green had very much faded leaving a yellow colour.

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The paper-type PCB is also normally a lighter colour, but instead, is now a toffee brown. It does have nice silkscreen labelling the components and connections, and some araldite adhesive on the transformers to provide a minimum amount of mechanical support. By chance, it seems the two high-voltage (HC 13002) NPN transistors were flailed out slightly which may have improved heat dissipation slightly by taking it away from other components. The capacitor itself still looks healthy after all this time, which seems unusual in my experience.

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A look from all sides reveals nothing unusual. A glass 2A fuse in heatshrink protects the primary, as a quality design should have. Pretty much all components are populated, although the pre-heat capacitor seems to be a different physical size to the footprint on the PCB resulting in a crooked mounting.

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A further check shows the capacitor is an Aishi CD11GE series capacitor, which is a highly impressive capacitor designed specifically for electronic ballasts with 12,000 hour rating at 105 degrees C, or 3,000 hours at 130 degrees C. Even more surprisingly, when tested for capacitance, its value was still spot-on, although the series resistance is probably a tad on the high side. I’ve generally seen no issues with Aishi capacitors, despite their name being less popular.

2016060319486486As the failure was a silent failure with no traces of catastrophic explosions or strange smells, I expected the fuse to be intact, and a check with the meter shows it is.

It seems likely that the ballast remains fully functional and if wired up to a large tube, could probably continue to provide service. However, as it’s already lived a long life, I decided I would scrap it in the end.

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A check of the resistance in the filaments seems to confirm what I was thinking – the electrodes had slowly failed. The filaments normally are 1-2 ohms, so I suspect the increased resistance is a sign they have been eroded and have lost their mass to some extent. The difference in resistance also seems to imply one filament has worn out quicker than the other. This is corroborated to some extent by the difference in darkening between the two ends. Once the emission coating is lost on the electrodes, the cause a lot of voltage drop and incapable of sustaining the arc within the lamp.

Conclusion

While I purchased this globe because it was special to me, I didn’t really have many expectations for quality or longevity, especially considering its origin. It definitely exceeded expectations and had a good run. It appears to have failed because the electrodes have degraded so far as to increase the voltage drop so far as to be impossible to start and maintain a discharge. It was nice to see that it didn’t fail catastrophically, and despite the heat and long operational hours, the components generally survived well and the ballast may have been reusable. Despite this, it was decided to dispose the ballast without exploring further reuse, although it has been done successfully in the past prior to my blogging (e.g. to drive 18w linear tubes).

The globe has since been replaced with an LED globe, which  sadly doesn’t provide as much illumination, but is still barely enough. Lets see how long that one lasts!

About lui_gough

I’m a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!

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