Load Testing Arcade PSU - Resistor Recommendations

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    • Load Testing Arcade PSU - Resistor Recommendations

      Will be working on some classics that have known issues with power regulation (Pole Position and Centipede). Will also be setting voltages for more modern arcade switching PSU's (Happ, Peter Chou, Sun). So that a PCB isn't made a sacrificial test board to test voltages, will build a harness or two that I will ground across each rail before to test/dial in voltages. Any recommendation for resistors for each rail?
      • Wattage/resistance/tolerance for:
        • 3.3vdc
        • 5vdc
        • -5vdc
        • 12vdc

        • and those odd-ball voltages for some of those classics
      Also, any particular resistor composition-type I should use: wire wound, carbon film, metal film, etc?
    • Say you want a decent load on each power rail:
      • -5V: 1A = 5W = 5ohm
      • +12V: 2A = 24W = 6ohm
      • +5V: 6A = 30W = 0.8ohm
      • +3.3V: 5A = 16.5W = 0.7ohm
      Those are just suggested power consumptions that should be ok with 90% of PCBs.
      However you're going to need BIG resistors that can actually dissipate such power and they're going to run hot.
      Looking for:
      - faulty Hang-On, Space Harrier or Enduro Racer (2203 sound board)
      - Sega Mega-CD 1 power board
      - Super Nintendo CPU (3 needed)



      "I'd 1cc games but I have a real life."
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    • Thanks @Apocalypse, the resistors shall only be there long enough to dial in voltages. I'm particularly concerned about the classics that I'll be working on like Centipede and Pole Position. I'll be bypassing the edge connectors on those and powering the board to the test points. For JAMMA boards, I will solder in the resistors to JAMMA fingerboards, dial in the voltages before hooking up the PCB's.
    • Apocalypse wrote:

      However you're going to need BIG resistors that can actually dissipate such power and they're going to run hot.
      This bears repeating...
      You'll want to be using the big ceramic resistors like at the bottom of this picture:



      acblunden2 wrote:

      the resistors shall only be there long enough to dial in voltages

      if you're using a normal 1/4W resistor, even for a few seconds that's enough to cause the wires in your harness to get hot and melt the casing right off of them

      Also, IMO it's kind of pointless to do this for adjusting the PSU, because the PSU's output voltage is going to vary depending on the board you have a attached.

      I've had a psu dialed in at exactly 5.0, with one board, then I put a large power hungry board on it and watched the voltage drop to 4.6, then without adjusting put a very low consumption board on it and watched the voltage spike above 5.6. This is the whole reason these PSUs are adjustable.

      If you're super concerned just dial it down before you power up and then slowly raise the voltage until you're set where you want it, and then reboot (since it likely didn't boot properly with low voltage).
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    • nem wrote:

      What @twistedsymphony said.

      6A on the 5V line is also a pretty substantial load. @invzim has measured the power consumption of a dozen boards and none of them consume that much. So if you dial the PSU for 30W most likely voltage will be high for whatever board you'll be connecting next, even an old power hungry board.

      wiki.arcadeotaku.com/w/PCB_Power_Consumption
      He has only tested small boards to me.
      Try with a full MVS 4 or 6 slot, SF1, Beast Busters, OutRun, Konami Twin 16, etc.
      But of course 6A is a lot but you want to have some margin.
      Double Dragon is already over the 4A mark and is far away from my hungriest boards.
      Looking for:
      - faulty Hang-On, Space Harrier or Enduro Racer (2203 sound board)
      - Sega Mega-CD 1 power board
      - Super Nintendo CPU (3 needed)



      "I'd 1cc games but I have a real life."
      01010011 01000101 01000011 01010010 01000101 01010100 00100000 01001101 01000101 01001110 01010101 00100000 01000111 01010101 01011001