Assy 250425 Rev. A

This is a Version B motherboard produced from 1984. Numerous chips surrounding the VIC-II (MOS6569) graphics chip have been replaced by a single clock generator IC (MOS 8701). The locations of the SID (MOS 6581) and the PLA (MOS 906114) have been swapped with respect to Version A-CR.

The inside of the machine:

All electrolytic capacitors and voltage regulators have been exchanged for new ones as described in the C64 Capacitor Mod.

The CPU, the VIC-II, the PLA and the SID chips all have heatsinks attached to keep them running cool. Heatsinks and thermal tape have been bought from the Retroleum.co.uk spares shop.

Capacitor C38 (51 pF) has been replaced by a 4.7 nF one to make the RESTORE key work like all the other keys as described in the C64 RESTORE Key Mod.

The outside of the machine:

 

© breadbox64.com 2015

3 comments on “Assy 250425 Rev. A

  1. I have one of these, made in England…. unfortunately … black screen. Occasionally I can get a garbled image…

  2. It sounds like you may have issues related to the PLA and/or Character ROM’s. I’ve had a similar problem with a long board motherboard (link)

  3. What does the switch on the RF modulator do? I only have the RF cable to connect to my TV and I’m wondering how this switch effects video/functionality. Also can anyone recommend anything to improve picture quality, that doesn’t need the Commodore video cable or a modification to the board?

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