ULA: 6C001E-7 (date code 8625, probably made in UK)
RAM: 48KB
Trivia
The original Issue 3 board was sold as defective and without the case. There was a reset wire and a switch, so I guess it was once in a ZX Spectrum Plus case. After that it might have served as an exhibit because it had some labels attached that were describing the components. A quick test showed that the ULA was working, but that D0 was shorted to ground. There was some soldering done on the board, so maybe there was a short somewhere.
Although the board might have been repairable, I decided from the start to build up a replica ZX Spectrum from the recovered parts.
History
2023-01-07:
Used MPS2369 as TR3, and the CPU clock was present.
Diagnostics said the original CPU was defective (missing /M1), replaced with new CPU.
New speaker got broken when I tried to fix it with hot glue. Removed it and used the original speaker instead.
Used a new transparent case with white keymat and faceplate. Assembled the system there.
2022-12-29:
I found that the CPU clock is missing. It seems to be related to TR3, where I used a BC-548C as unconfirmed replacement type. Ordered a set of MPS2369, which are confirmed as working replacements.
2022-12-25 - 2022-12-27:
Assembled the new board, with as many new parts as possible.
Power connector had a short circuit, was resolved when resoldering the DC/DC converter.
System does not start, only shows black and white columns on a magenta border.
2022-12-10:
Stripped rare parts from the board: Lower and Upper RAM chips, LM1889, CPU, speaker, keyboard connectors, coil.
1 lower RAM was damaged when I unsoldered it.
1 upper RAM was damaged when I unsoldered it. 5 more upper RAMs failed the memory test after unsoldering.
Many traces got damaged while unsoldering the components. The board is for the trash now, stored away as a souvenir.
2022-11-25: Bought a replica Issue 3B board (black with ENIG plating)
