I purchased this cute “little” transistor tester on Amazon. There are two models, the higher end one has USB connectivity. This test device checks diodes, LED’s, transistors, and some other PN junction devices.
I’m sitting here playing with it. Generating graphs of parts I’ve bought from Mouser and Aliexpress.
This first chart is a eight samples of blue LED’s I purchased on ebay many years ago.
Here are 8 ish samples of one watt LED’s. Huge variation here. Only two of them would actually emit light with the tester (they all emit photons when hooked up to a higher current power supply).
Here are three samples of what I think are counterfeit Mitsubishi 2SC3133 purchased on Aliexpress.
Last, here is a set of eight BD139 transistor purchased from Mouser. This plot shows hFE/Ic. 50% of the samples cluster right on average.
This will be an interesting tool to gainer deeper insight into the components I buy and stock. I hope it will make it easier to identify out of spec components purchased from Aliexpress (but honestly I’ve stopped purchasing from there because of the counterfeit problems.)