ATX Power supply for X68000 ACE HD

I’ve got a X68000 ACE HD and have been restoring it. The original power supply was dead and I was reparing it. However, even I fix the original power supply, it is for Japanese 100VAC and I am not comfortable using it with American 120VAC. So, I have been working on making a 120VAC power supply unit using ATX power supply along with the PSU repair project.

There are many people who have created PSUs for X68000 using ATX power supply.

I purchased the following items:

  • Pico ATX
  • 12V8A switching power supply (someone used the exact same power supply)

picoatx psu

Also I needed other materials:

  • 6 colors of 20 AWG wires
  • 2-pin screw connectors
  • Various connectors - see below for the details
  • Polyimide tape
  • 74HC04 IC
  • Resister
  • Universal board (small)

Chasis

I thought about 3d printing the chasis of the ATX PSU, but I didn’t do it for two reasons:

  • The PSU may gets hot and it may catch fire or melt. I am not sure that will really happen, but it was a concern for me.
  • The PSU will generates electromagnetic interferance (EMI). The 3d printerd case won’t block the EMI. Again, I don’t know how bad it is. It may not matter.

So, I decided to use the original PSU metal case. I want to keep or re-install the orginal PSU once it is repaired, I preserved all the cables. (Other people cut the wires of the original PSU.)

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I’ve used M3/8mm bolt and three nuts to mount the PSU. I’ve put two nuts below the PCB so that there’s enough space between the PCB and the metal chasis.

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Because the Pico ATX will be on the heat sink, I’ve wrapped it with polyimide tape. It isolates electrically and it can survive around 260C (600F).

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I didn’t want to cut the original wires. I’ve used a screw connector to connect the original power wires and the PSU.

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Wiring

X68000 ACE HD needs +12V, -12V, 5V, and 5V stand by. The handling of power-on is different from PCs, and you need to flip the signal. You can find many examples on the internet, and I followed them as well. I’ve created a little board with a 74HC04 and a resister.

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X68000 is a 30-year old computer and some of the connectors are obsoleted.

connector parts note
2-pin connector (x2) MOLEX 5195-2 Use 08701031 SPOX Crimp Terminal 18-24 AWG
3-pin connector AMP 171822-4 same as PC’s FDD connector, but 3-pins instead of
4-pin connector IDE Molex 4 pin female Typical old HDD connector
5-pin connector JST XH series (substitute) I couldn’t find the original one. 2.54mm pitch

Because I couldn’t find the 5-pin connector, I used JST XH connector for it. I needed to replace the 5-pin female connector of the bottom PCB, as well as the male connector of the original PSU.

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To put connectors to the wires, I needed a clumping tool. I bought Hozan P-707 and it is excellent.

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And with putting back the original metal lid back and the work is completed.

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