To speed up the process of writing and blanking ROMS i decided to replace the EPROM with a FLASH solution.

FLASH can be written much faster and also you just blank them with push of a button instead of shining 15 minutes of uv light into them... Neat.

After looking through my chip collection i found some 39SF040 in a PLCC package. These are quite similar to the used 27c4001 EPROMS (D23C4001E MASKROM). I also ordered some PLCC>DIP adapters. The Pinout of the FLASH in the adapter matches up with the datasheet (1:1 Pinout).

A short look in both datasheets showed that only 2 PINS are different. PIN1 of the FLASH is A18 and PIN31 on the 27c4001. PIN31 on the FLASH is WriteEnable. WriteEnable must be high when we read (low while writing). We can just bridge PIN31 to PIN32 on the adapter (and remove PIN31). PIN1 from the adapter must be relocated to PIN31. I did this with just a wire bridge and some kapton tape to prevent shorts.

It now works like the regular unit but with the benefit of way faster reprogramming. 

Would i recommend it? Probably not... EPROMS are cheaper. If you dont need the faster programming and blanking it makes no sense... :)