Hugo Holden
Veteran Member
Since I suffer from a spare parts disease, I saw a dynamic PET board on ebay, just like the one in my recently acquired PET, so I thought I would buy it as a spare.
Oddly because my original PET board had no hardware faults and I did not have a fault to sort out and repair. I find if I have a faulty board, I learn a lot more about it trying to diagnose and repair a fault. Seems odd but that is the way I learn about some designs.
So I bought this similar board, in the hopes that it might actually have a fault I could get to repair. I have not tried it yet.
This one has the extra bank of memory chips installed, hand soldered, no sockets, so I assume like my original board, it has the upgrade to 32k memory.
It has all original MOS ROMs it appears:
UD9= 901465-03
UD8= 901474-01
UD7= 901465-02
UD6 = 901465-01
UD5 = 901447-29
The thing is my original PET board did not have any IC installed for UD5.
What does the UD5 ROM do ?
Oddly because my original PET board had no hardware faults and I did not have a fault to sort out and repair. I find if I have a faulty board, I learn a lot more about it trying to diagnose and repair a fault. Seems odd but that is the way I learn about some designs.
So I bought this similar board, in the hopes that it might actually have a fault I could get to repair. I have not tried it yet.
This one has the extra bank of memory chips installed, hand soldered, no sockets, so I assume like my original board, it has the upgrade to 32k memory.
It has all original MOS ROMs it appears:
UD9= 901465-03
UD8= 901474-01
UD7= 901465-02
UD6 = 901465-01
UD5 = 901447-29
The thing is my original PET board did not have any IC installed for UD5.
What does the UD5 ROM do ?