Some time ago we expained how we fixed our EPROM programmer TOP2004. We saw that if we plug some BAD EPROM into the socket, the current peak at Vpp pin is too high and able to burn the switching Vpp transistor in the programmer. A bad EPROM like that is also quite hot so somehow you can touch it to check if it’s good or not.
Max current for Vpp switching transistors (MMBT3906) is 200mA; rarely we saw an EPROM in need of more than 100mA on the Vpp.
So we decided to mod our EPROM programmer, to protect it from bad EPROMS… we just cut the Vpp trace, and added a FUSE SOCKET for 100mA fuses, to protect it. Simple and effective!