Sure, the “Atomic Fusion EPROM Eraser” works fine, on days when Old Sol is cooperative. Unfortunately, depending on geography and time of year, the reliability of this method can leave a lot to be desired.
There IS another easy alternative, which while not as cheap as a foam pad in the sun, is still a lot more economical than commercial erasers. Go down to an electrical supply house or appliance-repair shop and buy a “Ozone lamp” or “Germ lamp” of the type used in clothes dryers to help give that “sunshine freshness” to your tumble-dried blue-jeans. Also pick up a socket for it, a regular 100-watt incandescent light bulb, and a standard socket. The total cost of all this stuff came to about CD$ 20, here in the backwoods of Canada.
The 100-watt bulb and socket will act as the ballast (and very big “pilot lamp”) for your EPROM eraser. DO NOT try to run the ozone lamp directly from 120 volts, or you’ll blow it for sure. Mount the two sockets on a board, with the “Ozone lamp” positioned such that you can slide an EPROM underneath it, almost touching the lamp. It’s also a good idea to provide an shield for the ozone lamp; while the amount of UV it produces is unlikely to cause vision damage when looked at briefly from a reasonable distance, it CAN cause temporary “spots before your eyes.”
2764’s take about 20 minutes for full erasure with this set-up. Don’t worry about heat damage, the ozone lamp doesn’t get very hot. I suggest only erasing one at a time; remember that light intensity falls off as the inverse square of the distance from the source, so the further the EPROM is from the lamp, the longer it will take.
If you really want to get fancy, pick up a 20-minute timer from the same appliance shop and place it in series also. Other amenities: a pretty box to enclose the ozone lamp/EPROM, a power ON/OFF switch, and a fuse.
Don’t just let your EPROMs cook while you go out for an extended time; in principle, they can be damaged by over-exposure. A final hint: for some reason, the first and last locations in an EPROM appear to be the last to erase. If you PEEK these locations and find them at 255, there’s a very good chance that the EPROM has been fully erased.