Quoted from Largemann:
I tried to burn a few unmodified U6 with the 25v vpp setting, and without the external burner. The writes completed and verified every time, but none would boot in the machine.
Sounds like the M2732As you have are no good or just not working with your setup. I usually don't bother adding the external power supply & they still burn ok anyway without it every time. If I have problems I add the power supply to rule it out.
Not sure about those 2732s from chipgate, it's too cheap for as start for genuine NOS Hitachi's & looking closely & comparing the logo next to "japan" the detail doesn't look quite like an original, it's blurred a bit, my guess is these are most likely the same new manufactured 2732s stamped with Hitachi stamp in this case - who knows, they are getting smarter all the time with fakes.
I have bought used/erased Hitachi eproms from funkward-tech, 2532, 2716 eproms as well, all work perfectly. I least you know they are genuine brand original eproms.
I have had eproms that verified OK then wouldn't work in the game, it happens - not sure why though.