Hello Berndt,
If the board you are trying to repair requires a '705J2 device, it is unlikely that you will be able to use the '705J1A device as an alternative. The '705J2 had significantly more RAM and PROM resources. Even if the code would fit within the smaller device, you would need to have the source code available to be able to re-assemble. This is because the address ranges for RAM and PROM are totally different for each device.
'705J2:
RAM: $90-$FF (112 bytes)
PROM: $700-$EFF (2048 bytes)
'705J1A:
RAM: $C0-$FF (64 bytes)
PROM: $300-$7CF (1232 bytes)I used the '705J2 device about 15 years ago, and still have a few of the windowed UV eraseable packages. I have long since lost the ability to program these devices - I did previously use an EVM board for programming, but this became faulty. This board also had an emulation mode for the '05J1 ROM device.
However, I would have some doubt whether the later JICS board specifically for programming the 705J1A and 705KJ1 devices would be capable of programming the 705J2.
In the light of this pessimistic outlook, please send me a PM if you still require any of my stock.
Regards,
Mac