iMac g4 usb and sleep problem

I recently installed a super drive in my iMac g4 15" 1ghz. After I put it back together, I discovered that I had pinched the airport antenna between the two halves. I took it apart and I had to take out the logic board to free the cable. After I put it all back together it started normally but when it got to the login window it gave me the "you need to restart your computer" message so I did, but when I restarted it, it got halfway through the startup chime then it went silent with a black screen. After a day of fiddling with wires I decided to leave it on at the black screen. When I came back a couple hours later it was at the login window but frozen. I restarted it and logged in it was working normally until it froze again about 15 minutes later, but I could tell it wasn’t frozen because the clock was still working. I changed the USB port that my keyboard was plugged into and it worked for another 15 minutes then stopped working again, but did not do the same thing on the third USB. I still get the black screen in maybe 1 in 5 startups and the USB problem hasn’t improved but it seems that it only freezes after periods of idle between 10 and 15 minutes. also the computer works fine but when I put it to sleep it wakes up about a half hour later. Also this may be relevant I washed the fan while it was apart because I am allergic to dust. I was wondering if it was possible that some water got into the power supply and affected it somehow? Anyway thank you for answers in advance.