- The Commodore 128DCR had a defective U19 colour RAM and serial bus lockups when accessing the internal disk drive or printer.
- The author replaced the U19 colour RAM with a new-old-stock M2128-15 SRAM but did not test it beforehand.
- A diagnostic test revealed bad colour RAM, serial port, user port, and suspicious CIAs, though the keyboard and joystick ports worked.
- The power supply and floppy drive mechanism were removed to access the logic board for repairs.
- After installing a socket for the colour RAM, the system displayed incorrect colours due to missing data line bit 5, requiring bodge wires.
- The replacement chip did not fix the colour RAM issue, showing stuck bits and inconsistent colours; the author suspects the chip may be DOA or other components like U20 or U55 are faulty.
- Disabling the ATN line on the internal drive did not resolve serial bus lockups, and the author plans to replace CIA #2 on a future visit.