ULA: 6C001E-7 (date code 8448, probably made in Philippines)
RAM: 48KB
Trivia
Was sold as “defective because it cannot be turned on”, which was correct.
Has a SN94459 video chip instead of an LM1889.
The system was probably repaired in 02/1987, where the CPU has been replaced with a Mostek Z80 CPU.
Known Issues
One rib of the grille is broken out.
-5V line is missing, for unknown reason. Other voltages are fine. I already changed all the relevant parts, but could not restore it. On one end of R79, -8V is present, but on the other end it’s just +0.5V. It started after washing the PCB, and one time I was able to restore the voltage while measuring, so it must be some kind of mechanical problem. I checked all solder joints and also resoldered all components, but it didn’t help. (PS: The schematics are incorrect. It’s basically like shown in “Issue 4B”, but with D19 and C79 swapped.)
Restauration Works
7805 was short and triggered the OCP of my power supply. After replacing it with a DC/DC converter, all voltages were back and the system started normally. Likely cause for this damage was an attempt to run the system with a power supply with wrong polarity.
System did not make a sound. After replacing TR7 and D9, sound was back. This might also have been caused by the wrong polarity.
Composite mod.
Case cleaned and some minor optical issues removed.
History
2023-03-11
Reassembled the system
System suddenly does not start anymore because -5V is missing.
