I bought usb to ps2 keyboard plus mouse adapter “USB Male to PS2 Female Cable Adapter Converter Use For Keyboard Mouse” from Banggood to connect some older hardware (especially on old bar code reader with PS/2 keyboard interface) to new computer. This particular USB Male to PS2 Female Cable Adapter Converter Use For Keyboard Mouse was both cheap (less than two euros) and had received good reviews.
When I received the product after two weeks waiting, I was disappointed that it did not work at all. The device was completely dead: computer does not recognize it at all and there was no power delivered to keyboard and mouse connectors.
This needs some more research to see what is wrong. So I opened the device. It was very easy to open the plastic case. And this revealed all the details what is inside and what was wrong.
As you can see the problem was loose 5v power wire that makes no connect to circuit board. I suspect that manufacturer did just did bad soldering job on this and bad quality control. I was lucky to find the problem this easily. I also fest lucky that the loose wire did not cause any more serious problems (like short circuiting to some wrong place like USB data wires or ground and thus damage computer USB port).
After I soldered the power wire to correct solder pad I go the adapter to work. It worked with one mouse I tested and also with PS/2 keyboard. But for my main task it did not work – the bar code reader that worked well with real PS/2 port on old PC did no reliably work with this adapter. Sometimes works, sometimes not, and when works looses more or less characters that should go to PC. I think that the bar code reader I had sends the characters to PC faster than my USB Male to PS2 Female Cable Adapter Converter Use For Keyboard Mouse can handle (needs more research to find out reason and if there is some reasonable fix for this).