Assy 250469 Rev. 4

This is a Version E PCB produced from 1987 (known revisions include Rev. 3, Rev.4, Rev. A & Rev. B). These motherboards are also known as the Commodore 64C short boards. The BASIC and Kernal ICs have been combined in a single ROM at U4. The keyboard connector and CIA #1 (MOS 6526) have changed locations. The PLA and various TTL chips have been replaced by a new 64-pin IC. The board revision introduced a new SID chip (MOS 8580) which runs at 9V, and a new VIC-II graphics chip (MOS 8565) running at 5V. The motherboard comes in two colors – yellow and green. More images of the two motherboards can be found below:

The inside of the machine with the yellow motherboard:

The CPU, the VIC-II and the SID chips all have heatsinks attached to keep them running cool.

All electrolytic capacitors have been replaced by new ones as described in the C64 Capacitor Mod (link).

The outside of the case:

The power LED color is red.

The green motherboard looks like this:

© 2017

9 comments on “Assy 250469 Rev. 4

  1. Very nice! I have this very same MB in the green variety. I received it with no RF modulator so I am interested in your RF replacement board. I have new power supply, all voltages appear normal on the board. But how can I actually tell if the board still works without video? Is there a way to test?

  2. Nice. I just picked up one with the yellow PCB. However, no heat sinks, but a RF shield with little tabs, that push onto the IC’s.

  3. It appears the keyboard mounts were separated from the original shield. Was this difficult to do? I want to leave out the shield on a C case I am working on but the mounts are semi-riveted. At the same time, I do not want to destroy the shield in the process.

  4. It should be possible to gently remove the keyboard brackets from the shield using a flat headed screwdriver. I have not done this myself on a long board, but it certainly should be possible.

  5. I was thinking about doing just that but I then realized the force needed using a screwdriver might be too great and I’ll see some damage. In the mean time, I remembered that I had a mount kit already stashed away. 🙂

  6. Hi Juri, I believe that the Assy 250469 Rev. B was the very last motherboard revision that Commodore made of the C64.

  7. I just got ahold of one of these (Rev A). You can see it here:
    When I got it the main fuse was blown. When I replaced the fuse, it did not blow again, but there’s no video. Actually there sort of IS video..but it’s blank. Seems like it might be a problem in the VIC area.
    I have SAMs schematics and other troubleshooting docs for older revision C64s, but have been able to find surprisingly little documentation with test points/pinouts on these newer chip revisions, etc. It seems like this info would exist somewhere (I don’t even care if I have to buy it), but I’ve found very little, and most C64 troubleshooting books don’t take these late models into account. I’ve found a few rough block diagrams, but not much else. Any additional info anyone could add for how to find some documentation on this thing would be greatly appreciated.

Leave a Comment