Checkerboard or no display usually means memory is bad, replace all 64k ram chips. Oddball problems usually traced to the VIA ic's blown by unbuffered lines. Real easy to do to blow it if careless! Make sure you put the shield back on with those finger "pads" coated with bit of heatsink paste on them, they're like poorman's heatsinks! The video IC get brutally hot! Monitor the voltages for stablity and good idea to replace those big capacitors just in case. The floppy drives I think is belt driven type and needs bit of cleaning. I had a problem with one, inside that small can there's 2mhz crystal and one TTL chip, That TTL chip was baddie. Jason D.