Electronic – unusual transistor markings “C8550”

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I am repairing a "wall-wart" charger for a Black and Decker battery powered edger which uses a 12 volt/7 amp hour battery. It has ceased to deliver charge current to the battery but the half wave rectified current is present at what I think is the emitter of a TO92 cased device labelled "S8550". I have found confusing information trying to identify this device. I found a reference to an "SC8550" that is listed as a PNP silicon transistor but I have never seen an SC designation without the preceding "2". It does not check as a "good" PNP transistor using the DVM and I don't have access to a curve tracer.

Does anyone have experience with this "transistor"? If the info I found is correct then I guess I can search using the max ratings to find a sub. It is the only transistor on the small circuit board which also contains a quad op-amp.

I don't have a circuit diagram/schematic and I am unable to determine the purpose of this device except maybe it is a switch to supply charge to the battery until it reaches a specific charge level? Is it likely that a TO92 cased device would control current to charge a 7 amp hour battery or might this be a voltage reference?

Best Answer

This is a really common cheap and generic PNP power/switching transistor in mainland China. It's inspired by the 2SC8550, but specs and pinouts vary (usually Japanese or US pinout, IME).

Other similar part numbers are SS8550, SC8550 etc.

It is often quoted with a silly high power dissipation intended for audio output type ratings.

Example datasheet of a similar part here.