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Sylvania LED Bulb Autopsy (Front)

Sylvania LED Bulb Autopsy (Front)

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Here’s the front of the bulb after I removed the plastic top. There is nothing visibly wrong here. When I get through the back of the bulb, I will be able to see if there is anything wrong on the other side. When I was cutting at the plastic housing, I could hear the characteristic sound of glass fiber reinforced plastic. It was also rather thick. The plastic housing is probably the best part of the entire bulb. It also surprised me to see only four LED chips on the front. I was expecting a larger array.

A79F50AD-C858-4FA7-BCAF-36FA81C0AB57.jpeg E816A592-B997-47F1-90FD-D3B9088CF32D.jpeg 6987A0A5-3143-44E3-9B06-0858EA7896C6.jpeg

Light Information

Light Information

Manufacturer:Sylvania/LEDVANCE
Lamp
Lamp Type:LED
Filament/Radiator Type:LED
Base:E26
Shape/Finish:A19
Service Life:10000 hours (In reality probably more like 500)
Electrical
Wattage:6w
Voltage:120v
Current:95mA
Optical
Lumen Output:450lm
Lumen Efficacy:75lm/w
Color Temperature:2700k
Color Rendering Index:87 CRI

File information

File information

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Filename:E816A592-B997-47F1-90FD-D3B9088CF32D.jpeg
Album name:Mr. Orthosilicate / LED crap
Keywords:Lamps
File Size:401 KB
Date added:Sep 26, 2019
Dimensions:2464 x 1848 pixels
Displayed:68 times
Date Time:2019:09:25 16:41:49
DateTime Original:2019:09:25 16:41:49
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James
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Sep 26, 2019 at 11:39 PM Author: James
From the style of the connector on the PCB, it looks to me like a lamp made by Leedarson of Xiamen. If these fail early, in my experience it is often due to a fault of one of the input filter circuits, so you may find that the fusistor connecting the lower PCB to the lamp cap has blown. Leedarson has excellent quality control and automated X-Ray inspection of every PCB on many of their high speed assembly lines, so microscopic soldering defects that can cause failures with other LED lamps to fail early are not so common with them.

When you open the rest of the lamp please post a photo of the other side of the driver, this looks like one of the newer ones with a linear driver. I would be curious to know if the main IC is from BP Semiconductor. That seems to be becoming one of the principal suppliers of IC’s for LED retrofit lamps.
High Intensity
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EYE 175w MV


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Sep 27, 2019 at 01:08 AM Author: High Intensity
The design looks very similar to this dollar store LED bulb i took apart a while ago.

Old lighting is, and will always be, the best lighting.

Medved
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Sep 27, 2019 at 04:40 AM Author: Medved
@James: "linear IC" - well, in fact it is nothing more complex than just a simple power JFET transistor (gate to negative rail, source via a resistor to the negative rail, drain feeds cathode side of the LEDs): The cut out voltage, with the "Isense resistor" in the source is all what forms the linear current source.
These are made by many semiconductoir companies now, it is indeed becoming the most popular ballast concept.
The three main advantages: It is simple and compact (so it fits into e.g. base of the full glass bulb filament designs), it is cheap and it inherently does not generate any RF disturbance.

For the fault: It seems they are using smoothening electrolytic capacitor after the rectifier (behind the bottom connector). If the lamp has some hours on it, I would suspect that failing, leading to the fusible resistor acting.
If you may tolerate some 120Hz flicker (similar to fluorescents) and a bit lower power, you may just cut it out and leave the circuit without that. The resulting light output would be about half, the dissipated power less than half, so it will run way cooler.

No more selfballasted c***

Ash
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Sep 29, 2019 at 01:45 PM Author: Ash
How would the capacitor failure (i assume by reducing capacity and growing ESR, not catastrophic failure) cause the fuse resistor to burn ?
Medved
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Sep 29, 2019 at 02:00 PM Author: Medved
With these high voltage ones, the dryout under load (significant ripple current present, causing it to overheat due to increasing ESR) uses to be accompanied by flashovers, so mabe temporary, but still short circuits. Unlike many modern SMPS, this circuit conti ues operating quite decently even when the capacitor increases its ESR, without any big effects (only slight 100/120Hz flicker and gradual reduction in brightness - neither fast enough to get notices), so it uses to remain in the circuit till it really flashes over and so causes the short circuit.

No more selfballasted c***

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