Try the steps from
easy to
difficult:
1. Reseat the chips, maybe spray them with some contact cleaner (I use Contact cleaner 390 from Kontakt Chemie for years now and it served me very well)
Make sure you get rid of any static electricity by touching the radiator with your hands or washing your hands with streaming water.
2. Check whether the PSU outputs the correct voltages with a multimeter. You can find the corresponding voltages of the pins by googling something like "amiga psu pinout"
If these are too high, don't despair, your Amiga will likely still work perfectly fine, but you most certainly found the culprit
Also if the PSU has the right voltage, it might still be the main problem, if it's plugged in into the Amiga and turned on it might not keep up the voltage needed. Anyway, a spare PSU is never a bad idea. You can get one at vesalia.de:
http://www.vesalia.de/e_a1200psu[8809].htm
3. Check for leaking capacitors. Not all are easily tracable, but most often you can see it immediately. If you can't find any, try to trace leaks with an uv-lamp.
Replacing a capacitor is easy. They have only two pins and you have to replace it with a capacitor of the same capacity in (micro)Farads and type (electrolytic or not). Check whether the capacitor has a 'minus' mark printed on it. It means it is an electrolytic capacitor, and if you replace such a capacitor (with also an electrolytic capacitor) you need to remember where the capacitor pin on the side of the minus mark is located on the board (ergo
write it down). Soldering such a capacitor the wrong way around and it won't work.
Aside from replacing a drive belt in the floppy drive, this should enable you to repair your Amiga (and perhaps also many other devices)
