I've had very high success rates burning a variety of chips including 27c010, 27c1024, 27c4002 and 27c4001. I'm using a Mcumall dual power programmer, and am using USB and a 12v power supply to power it.
When I try to burn 27c020 chips, it gets all the way to 99% and fails. If I dump the failed burn, and spot check it against the original image that i'm burning, the data is very inconsistent and corrupt.
I'm fairly certain the chip is not at fault. I purchased it about 3 months ago pre-loaded with data. This is the first time I have erased and reburned this particular chip. Any suggestions other than switching chip brands for the 27c020?