I pulled about 20 TMS27C040 from a parts board and they all erased fine.
The problem is they all program about dozen or so bytes and then fail.
The TI datsheet says VPP 13V and pulse 100Ás, that's what my programmer
defaults to when I select the chip.
Is it possible that all the chips are just tired or more likely that the programmer
isn't configured properly to write these?