Hi there! I'm sorry, I'm afraid I don't know enough about the peculiarities of PC1512/PC1640 to make a diagnosis.
Because of this, I can only gibe some general tips.
It's not much, but I don't want you to stand in the rain, so to say:
If the system disk DOS Plus based, it might be an explanation (PC1512 came with DOS Plus, GEM and MS-DOS 3.x).
DOS Plus is fascinating, but also very picky.
Here's my little adventure with DOS Plus 1.2:
How to install DOS Plus (PC1512 version) ?
So if you can, please try a normal MS-DOS or PC-DOS boot disk first (v3.30 or higher).
That way, you can see if the Gotek is working so far.
Anyway, good luck!
🙂
PS: Other replies welcome! If someone has an idea, don't hesitate! 🙂
"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel
//My video channel//