The rare KU14194HB C64 Motherboard schematics and layout. Retraced in and imported from SprintLayout.

Disclaimer

This PCB is a replica. It includes the mistakes that Commodore made.

It is necessary to cut a trace above R37 on the bottom side, and add a 1K resistor from R37 and up to a via. See the images folder to where to cut and add a resistor.

Piggyback a 100nF capacitor over CR1.

Notice how the main crystal oscillator Y1 body is grounded with a wire.

In later designs 250407 Reb B I think, 4 piggybacked diodes were introduced to protect the serial lines when hotplugging the disc drive. I haven't added these myself, but I see the value of having those. I might add instructions here later on how to add the diodes.

Please see the BOM file.

The interactive bom html page is useful for assembling the board and finding signal traces by using a web browser. Try it here. For a BOM for ordering parts see the BOM above.

• Feel free post questions in the issues section. I will provide more information here later.

• 2020-01-23: V1.4 PCB improvements:
  • Expansion Port: Larger round solder pads for the shield. Same error in the original.
  • Expansion Port: Connector moved to center of shield. Some traces moved.
  • Left edge: Extended the PCB by 2.2mm.
  • Left edge: Increased track width of the power rails.
  • CAN shield: added two solder pads.
  • RF modulator: added solder pad.
  • Schematics: Rev 1.4. No change.
• 2019-11-12: V1.3 Fixes: Mostly missing values.
  • C88: "1000uF 25V" -> "470uF 50uF". Commodore said 1000 but used 470.
  • R31: "180" -> "1K". A mistake in the commodore schematics.
  • R52: "?" -> "330"
  • R53: "?" -> "100"
  • C86: "?" -> "82pF",
  • C36: "0.1" -> "20pF",
  • R22: missing trace. R22 = 0 Ohm. Parallel to C87 (NC). R22 doesn't matter.
  • C101: is a Y5U. VIC2's decoupling cap. Has a higher dielectric rating. Doesn't matter.
  • C70: 15pF 5%. This is a PAL only board. In later revisions, 16pF is used for NTSC.
• 2019-11-10 V1.2 Added missing C14 10uF 25V electrolytic capacitor
• 2019-10-15 V1.1 Layout: Fixed missing keying-slot in user port.
• 2019-10-05 V1.0 First release.

A playlist of all the videos:

forum64.de: The board has some threads at forum64.de (German). May require login.

• Bilder SHOWROOM für Repro-Boards... KU-14194HB
• KU-14194 Bestückungs-Thread
• KU-14194 (long group buy thread)
• KU-14194 (Replika) ... wer schafft es als Erste/r? Aktuelle Sachstandsberichte ...