The second mod that was tried

Aurangzeb,
Without a scope, you are groping in the dark.

The only chance you have of this device actually programming reliably is to follow the instructions exactly.

If you, after modifying everything manage to make a chip "program" what knowledge do you have that fuses are blown - not broken or that flash capacitors are fully (dis)charged.

Fuses broken, not blown, have been known to regrow and insufficient (dis)charge of flash capacitors dramatically shorten the retention.

It stands to reason thet the original designer of this device verified that the pulses were correct but you - by own admission - have absolutely no means of verifying that after your "modifications".

Again, you are fighting the wind, go get some ISP chips and take this as an experience,


Erik