This article describes the internals and basic test of a no-name Chinese 4′ T8 LED replacement.
The lamp is a Type B DEP (double ended power) configuration, cool white, it requires rewiring of a traditional magnetic ballast fitting or e-ballast fitting. Don't attempt this unless you have the needed competencies.
It has no rating label, no information about its configuration on the lamp, no warnings about compatibility… so very Chinese.
The lamp is rated at 18W 1750lm, claimed life is 50,000h but you should take that with a grain of salt. The lamps cost $6.40 ea in a pack of 10, including delivery. They were well packed and the pins had a small plastic protector.
Above, the powered end of the LED strip and the LED driver partially withdrawn from the hollow aluminium extrusion.
The LEDS are 2835 SM types, they are in two parallel series strings of 48 LEDs requiring about 150V drive. 106mA, 53mA per string.
Surprisingly it measures 18W input power, probably 16W to the LEDS, 170mW per LED, around 100lm/W overall luminous efficiency.
Three tubes were tested for an hour each. No LED failures, input power did not drop below 17W.
Light output was measured at 430lx at 1m at right angles to the centre of the new tube after an hour.
Above is a view of the inside of the pin cap, both pins are bonded. This is not always done in DEP tubes.
Above is a view of the inside of the other pin cap, both pins are bonded. This is not always done in DEP tubes.
These are easily dismantled and reassembled, and potentially repairable. Swapping LED drivers or LED modules with compatible parts from a failed unit is feasible, replacement of individual LEDs appears practical but I have not (yet) attempted it. In my use experience, two of four similar type of lamps failed after 10,000-20,000h, one LED driver and on the other a single LED knocked out a quarter of the lamp (a 4×24 LED configuration).