Tech Tip #14 - Protect your Eproms from Light !!
Another not-so-obvious Eprom issue you should be aware of....
Erasable Eproms (the Roms with glass windows on them) SHOULD 'at all times' have some form of sticker covering the small glass window....
Typically most games will have a sticker/label on then to indicate which game and version it is.....
But, leaving a sticker off, will allow stray light to enter the window and start corrupting (erasing) the data....
For those that don't know, Eproms are erased blank simply by exposing them to Ultra-Violet light for 10-15mins using an Ultra-Violet eprom eraser available at places like Jaycar, Altronics, ebay etc... (you can leave them out in the sun for 15-30mins to achieve the same thing).
Eproms are fairly safe within a dark headbox, but stray daylight coming thru the rear air vents of the headbox may cause trouble over time, other than that, leaving your MPU board on your workbench or out in the shed for a week or 2 (with lots of stray sunlight+reflection bouncing around) is enough time for your board to become corrupt.
Overcast days are no better, it'll take longer than a sunny day, but it can do the same erasure...
So, at the end of that day, keep those stickers ON your ROMs ;-)
and make sure the stickers arent simply white paper stickers (they let light thru them).
Use a good solid label preferably with the silver or black backing on the label.
(real Eprom stickers from waaay back are either an adhesive thin aluminium sticker, or an aluminium-backed paper label).
Update:
Note that it's possible to over-erase Eproms in a U.V eraser, if you leave them exposed to long (30mins to 1 hour or more) the rom can become permanently burnt in, and then you can't program them anymore.
MM.
Tech Tips are brought to you by me, and are aimed to assist beginners and advanced users.
Common sense is sometime so common that everyone ignores it ;-)
