I have two oldschool playstation1 controller and I decided to connect them to PC via USB. One of them was faulty, because left side buttons (arrows and L1 L2) doesn’t responded for pressing.
I disassembled carefully: there are 8 screw at the back:
Then you can open up the plastic case:
I lifted up the PCB and started to check with multimeter. I measured and checked the continuity of PCB components, resistors, condensators, wires etc..
The fault was 2 little hairline crack on the pcb trace. I added a small amout of solder to this area and after the controller started to working properly.
For USB connection with PC I use this playstation usb adapter. You can order from ebay for only 3-4$.