// 2024-09-18 // by Elder0010
This machine has been assembled using a non functional board. No wonder why someone gave up on repairing this one in the past… it had all the faults of this world! I found U23 / U24 DRAM already replaced, which is quite common when the dealing with the dreaded MT DRAMs. One of the RAM multiplexers has been replaced as well in the past. I found another MT DRAM (U10) together with U13 (74LS257) RAM multiplexer dead. With further analysis, also U27, U14 have been found non functional. It finally started to boot, but the BASIC screen had screwed colours. Easy fix, it’s U6 (2114 SRAM / Color Ram). No keyboard input issue has been solved by replacing one CIA (U1).
Many of the ICs I found on this board have “sparse” datecodes. There’s even a MOS 6569 R5 VIC-II which hardly belonged to it originally. Perhaps this one has been used a sacrificial board for testing purposes?
I put this one in a empty case with a battle scar (matching, isn’t it?) I had laying around. All machines, even the desperate cases like this one, deserve to live again!
Faults: black screen, garbage screen, wrong colours in the startup screen, keyboard not working, no sound
Added missing MOS 6581 SID
Replaced 1X 4164 DRAM (U10)
Replaced 1X 74LS257 (U13)
Replaced 1X 74LS08 (U27)
Replaced 1X 74LS139 (U15)
Replaced 1X MOS 6526 CIA (U1)
Replaced 1X 4116 SRAM (U6)
Faults: slow power up, random crashes (23/06/2025)
Replaced 1X MOS 6526 CIA (U2)
Replaced Power Switch
