My lovely girlfriend bought me a broken PS2 Slim for my birthday so I could have fun fixing it. So you can imagine my surprise when I plugged it in and it worked perfectly. But with that being said, I could see that the console was dirty, so I took it apart to do regular maintenance. What I found inside was pretty gross. Unfortunately I forgot to take any pictures because I was kind of in the zone, but there were some dead bugs inside the console. It was so sticky that I really struggled to pull the pieces of the console apart. After fully cleaning it, I reassembled it and was ready to play it. It turned on fine, but after inserting a disc, absolutely nothing would happen. The laser wouldn’t engage, the disc wouldn’t spin, and I was just stuck in the startup menu. I was pretty disappointed at this point, because I started with a fully working PS2, and was currently left with a broken PS2 after having cleaned it. I unplugged and re-plugged the ribbon cables, cleaned the laser, and manually engaged the disc tray sensor buttons to ensure that the console knew the tray was closed. All of these efforts did not create different results.
At this point, I was back to the drawing board. I read online that the disc tray sensor buttons could sometimes fail, which could cause the disc drive to never initialize. I tested continuity with my multimeter, and I found normal results (no continuity when unpressed, continuity when pressed), so I knew that that couldn't be the problem. I took another look at the board underneath the microscope, and I did eventually notice something that could be the issue. Right next to the disc drive ribbon cable, there were a couple pins on a chip that appeared to be oxidized. It's possible that they had continuity before I disassembled the console, but then after flexing and moving the board, I broke the connection. With no other ideas, I decided to add fresh solder and reflow the pins. Once they were looking nice and shiny again, I gave it another try, and I was extremely pleasantly surprised to find that that had been the issue! After closing the disc tray, the laser immediately initialized, and the disc started spinning.
I am really proud of this repair because I felt like I was able to troubleshoot really effectively. There wasn't an exact guide I could follow online to solve this problem. Instead, I looked into common issues, and then when those proved unhelpful I figured out the actual problem on my own. Additionally, I soldered the pins on the chip without bridging any pins or running into any other issues. I am still not completely confident in my soldering abilities, so I am always happy when I can solder something well.
UPDATE: after selling this PS2 Slim on MarketPlace, I was made aware of a huge error I had made. The buyer let me know that the console was not reading PS2 games. I was puzzled because I had tested multiple PS2 games after fixing it, so I didn't know how this could be the case. Come to find out, some PS2 games are CD-based and others are DVD-based. All of the games I had tested happened to be CD-based, so I never tested a DVD-based game. I drove to the buyer's place and swapped out the laser. After doing this, both CD and DVD-based games were working. The buyer also had another PS2 slim on hand that had the opposite problem — it read DVD-based games but not CD-based games. I swapped the laser on that one as well, so then both systems were working for him.