I am new to this type of EEprom, appreciate some advice from the master.
I am using a Intronics pocket programmer to copy the content of the old EEprom 28c64 to a file and it successed but when I try to program this file to a blank EEprom 28c64 it fails!
If you can read it then you need check the Vpp pin of the programmer when you doing the programming. It should be 12.75V or 21V or 25V depend on your chip Vpp speicification. If the Vpp is correct, then your software has bug.