You could review some of the "Big Clive" videos on youtube. He's taken apart just about every LED lamp known & discusses the circuit, operation and failings etc. In most cases he's drawn the schematic & seems to have a good source of datasheets for the ICs. RP On Fri, 2 Nov 2018 at 03:00, John Coppens wrote: > Hello all. > > I've been really surprised at the variations of the circuitry inside > LED bulb replacements. A while ago, I bought a couple of bulbs ('Great > Value'-brand, a local Walmart product), which started showing failing > after just a couple of weeks. Opening them up showed that they were > fed by just a (linear) series regulator. So much for green energy. > > Now I acquired a couple of OSRAM bulbs, and opened one up just to > investigate. It did have a switching current regulator, but it used > a 4-pin chip for which I could not find any data. In fact, I didn't > find _any_ 4-pin current regulator IC. > > I've attached the circuit. I suspect the 1.8 Ohm resistor to be the > current-determining component. Strange is the (I suspect) transformer > which is actually across the LEDs (I'm not positive about it's > internal connections. I measure 10 Ohm across two pins, 14k across > two other pins, but without unsoldering). 12 LEDs (I suspect triplets) > are connected between + and -. > > Does anyone have an idea which IC this could be? It's marked 9938F > and S1C01X. No logo as far as I can detect. > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .