I recently swapped out a load of lighting at home, so it was an opportunity to take some of the older LED bulbs apart, to see how they are made : ) Last week, a Philips MASTER LEDspot was taken apart. This week, it is the turn of the Sylvania RefLED!
Full model details: Sylvania RefLED Reflector R50 510lm 8W 830, 220-240W, 50/60Hz
These were just moderately efficient at the time of purchase two years ago (about 64 lumens/watt), but nowadays there are more efficient models available. I have to say, the light quality from them was really nice - 3000K, which is semi-warm-ish but not overly warm such as an incandescent bulb, and really modernized the place - it's my favourite color temperature for home lighting now.
It comes with a Small Edison Screw (SES) or E14 fitting, which is quite small. It doesn’t leave a lot of space for the circuit board, so I was curious how they managed to squeeze that in, as well as heatsinking.
It proved hard to remove the translucent cover, so I had to take a cutting wheel to it. After I did that it was plain to see why it had been so hard; the cover was glued onto the heatsink frame of the LED bulb.
The entire unit is comprised of the following main pieces; the translucent plastic cover (it’s not really a lens), a cast aluminium outer frame which serves as the heatsink, 13 LEDs on a metal core printed circuit board (MCPCB), a plastic rear cylinder containing the LED driver circuit board, and a stamped metal end cap assembly. The MCPCB is secured to the heatsink with just a couple of small screws, and there was heatsink compound on the underside (the cast aluminium heatsink is machined on that surface but there are noticeable fine machined ridges on it).
The rear plastic cylinder is also secured with two small screws. The metal end cap was bizarre. It was crimped onto the plastic rear shell, and there wasn’t any wire soldered to it. Instead, the wire was just held by the crimp action. The other electrical connection (the insulated tip) was soldered. Interestingly there was a heat-shrinked resistor (10 ohm - I measured it) that was in series with the mains connection.
LEDs and Circuitry
The LEDs were series-connected. Each LED has the forward voltage of just a single LED (i.e. there is not a series array of LED chips inside each LED component, because it was possible to faintly begin lighting up the entire module starting at about 30V (2.3V per LED).
The circuit was slightly simpler than the Philips LED bulb that was torn down last week. The transformer was unusual in that it was soldered using two pins to the PCB, and then two more connections were on flying leads as you can see in the photo below. There was a bit of Kapton tape covering the end of the PCB with the transformer, which was removed for the photo below.
For the photo below, I splayed out the capacitor to see the integrated circuit hiding underneath : )
Unfortunately I have no detail on it; it is marked 13A19A HD50 and I couldn’t find a reference to that online. It is the only integrated circuit on the board.
The underside contains a bridge rectifier marked 10T10 and on the left side there is a small diode in the photo below.
Lighting it up
I’m not sure what manufacturer LEDs are used, but from the shape and size of them, they could be Osram perhaps. I was convinced they were Osram 'Duris E 5' range, but I have some of those and the bond pads look very slightly different underneath the phosphor coating. The photo below shows the LED chips barely lit (at about 30V).
At 33V, the current is still tiny (1.5mA) and yet the LEDs are very bright, certainly usable for a small kids torch, with very long battery life! at this level : )
I was slightly disappointed that visually this LED bulb appeared less well made, in comparison to the Philips one. However, in Sylvania’s favour, it is a design that is several years old, whereas the Philips one is far more recent. Also, none of these LED bulbs actually failed; I had ten of them for two years, in heavy use (especially during the two winters when it is dark by mid-afternoon - and I work late throughout the year and so some lighting is nearly always on) so they were reliable, and the light quality was really great during the two years I used them. Compared to normal users, we probably ran these LED bulbs for several times longer each evening. So my two years of heavy use could translate to 5-6 years of typical use before visibly dimming.
They had visibly dimmed after my two years of heavy use, but are still usable. So, I don’t feel too disappointed because they were worth the cost, providing far better light than the tungsten bulbs they replaced. And I preferred the slightly cooler light from them compared to the current SES fitting LED bulbs I’m now using (Philips MASTER LEDluster – too warm a color temperature for my liking but these bulbs have lots more light output though and exceptionally efficient.).
Times change, and so purely because I wanted more light and more efficiency that is possible with LEDs today, I changed to the Philips ones, but I'm sure there are new Sylvania models too that could be interesting to try. If you do, let me know which models are interesting so I can try them sometime too.
Thanks for reading!