Hugo Holden
Veteran Member
I had a go at making some spare ROMs.
I acquired some Japan made TMS 2532's and some Mil Spec Tesla made MHB 2716C's. This type has the same programming voltage as the original 2716, and both these types can be programmed by the easy to get GQ-4x programmer. Because the ROM's I got were NOS they didn't need to be erased, so that saved some time.
The thing that worried me the most was reading the original ROM's and that I might damage them with an error, which perhaps could include reverse insertion into a socket, or maybe accidentally attempting to program them and applying the 25V to pin 21.
The programmer of course is entirely software control. It does not have a hardware programming voltage disable switch (that I could find) so it relies on the software working properly and the operator not doing something stupid. It sort of reminded me though of the Ariane 5 flight 501 rocket failure, caused by a software defect. My feeling has always been that machines with software control should have a hardware control system, not allowing something to be pushed past its safe design margins, even if the software loses the plot.
So I made a dual socket adapter to use while reading the original ROMs, which isolated pin 21 of the IC being read and tied it to the supply pin 24, so that pin 21, where a high programming voltage could accidentally be applied became isolated from the programmer. So if I clicked on WRITE in a fit of madness, the IC would not be damaged.
I successfully copied all the ROMs and they also work in the computer. And the original ROMs are all ok too.
To label them I used sticky builder's aluminium tape for light occlusion and on top of that, black on clear tape from a Brother label machine. I figured if I labelled them with their pcb/schematic identity I'd be less likely to mix them up.
I acquired some Japan made TMS 2532's and some Mil Spec Tesla made MHB 2716C's. This type has the same programming voltage as the original 2716, and both these types can be programmed by the easy to get GQ-4x programmer. Because the ROM's I got were NOS they didn't need to be erased, so that saved some time.
The thing that worried me the most was reading the original ROM's and that I might damage them with an error, which perhaps could include reverse insertion into a socket, or maybe accidentally attempting to program them and applying the 25V to pin 21.
The programmer of course is entirely software control. It does not have a hardware programming voltage disable switch (that I could find) so it relies on the software working properly and the operator not doing something stupid. It sort of reminded me though of the Ariane 5 flight 501 rocket failure, caused by a software defect. My feeling has always been that machines with software control should have a hardware control system, not allowing something to be pushed past its safe design margins, even if the software loses the plot.
So I made a dual socket adapter to use while reading the original ROMs, which isolated pin 21 of the IC being read and tied it to the supply pin 24, so that pin 21, where a high programming voltage could accidentally be applied became isolated from the programmer. So if I clicked on WRITE in a fit of madness, the IC would not be damaged.
I successfully copied all the ROMs and they also work in the computer. And the original ROMs are all ok too.
To label them I used sticky builder's aluminium tape for light occlusion and on top of that, black on clear tape from a Brother label machine. I figured if I labelled them with their pcb/schematic identity I'd be less likely to mix them up.
