Whose design did the Chinese "knock off" and are there any known circuit diagrams?
Chris Williams
The earliest thing like this I've seen was around 1982 to 1985 from Taiwan. It was a plug-in board for an Apple ][ computer from a company that called themselves 'Fairy' in the software, along with a couple of large Chinese characters that I couldn't read. The Fairy tester would check TTL, CMOS and a handful of other parts, and like this one it'd identify the unknown part if it wasn't blown. It didn't do transistors or zeners, and certainly not optos. The design was similar to this one (port expanders and a big handful of resistors, 3 resistors per pin if I remember right. I reverse-engineered a schematic for it in case it failed, as getting service out of Taiwan (then) was about as easy as getting service from China (today). It worked, and saved me the cost of the board within the first few months of use. Sorry, I didn't keep the schematics for it after the Apple and all of my 'stuff' for it went to a landfill in the '90s.
Ha! As I was writing this, I googled it and found some info on that old card:
http://www.appleii-box.de/H055_AppleIIFairyICtestcard.htmas well as this article on other antique IC testers:
http://www.computernerdkev.heliohost.org/ictesters/index.htm