White Screen - Sega New Astro City Cab...HELP

    This site uses cookies. By continuing to browse this site, you are agreeing to our Cookie Policy.

    • If you can, take a few pics of the entire board and the underside.

      You have to test a few other parts on the PSU. Of course, you test the components with the power supply off.
      Start by testing the pair of switching transistors using an ohmmeter or a digital multi-meter set to the diode test range. Check each transistor for a short between emitter and collector. If shorted, replace them. Also, blown transistor are due to bad capacitors, check those too. Whatever you find bad, replace.

      Like Mitsu said, never power up the power supply without a load on it, bad things happen.

      Once you have replaced the failed components, the supply should be tested under
      load. Instead of using a game board, just in case, use a 1 ohm 50 watt resistor to create a "dummy load", connected between the +5 volt output and ground (DC COM), it will draw 5 amps from the supply, which is adequate for test purposes. You can also add a 5 ohm 50 watt resistor to the +12v line and ground. Test away to make sure you have all your proper voltages.

      Let us know how you make out.

      The post was edited 1 time, last by Derick2k ().

    • MissionFailed wrote:

      thanks Derick. you all have helped loads. I pulled the PSU out and took a look. Found the issue :D , Looks like a blown Resistor. ;( <X
      also the 12 volt fuse was inside the PSU. tested, had continuity
      Nice one Derick2k. That's the kind of support we love seeing here.
      * Arcade-projects, the site where you get the most of your arcade games.
      * If you want Drama go to Neo-Geo forum ---Darksoft
    • photos of the entire board and the underside. Blown switching transistors (Orange), Blown resistor(Yellow)


      when i was removing the PSU from the cab i noticed the heat sink mounted to the single (rear) switching transistor was loose and wiggling. Looking at the bottom of the PCB , the solder anchor points for heatsink where cracked free along with the transistor
      Hi Res Photos Top, Transistor part side, Bottom, Transistor solder side, heatsink anchor
      Im test all the other parts now, not look too good.. X/
    • Yup, just what I thought it would be. If you are ok with testing and replacing the parts, I would. You would end up with a much better supply than oem.

      Also, check diodes to make sure they are not dead shorted.

      Give it an overhaul, replace as need or all:

      Caps - Replace all the output filter capacitors with low ESR caps regardless of whether they appear to be good or bad, buy Nichicon caps.

      Transistors - Replace with original or replacements

      Diodes - Diodes on the output stages if bad need to be replaced with high speed diodes, they are not regular diodes.

      Hope this helps you out some.
    • Derick2k wrote:


      Once you have replaced the failed components, the supply should be tested under
      load. Instead of using a game board, just in case, use a 1 ohm 50 watt resistor to create a "dummy load", connected between the +5 volt output and ground (DC COM), it will draw 5 amps from the supply, which is adequate for test purposes. You can also add a 5 ohm 50 watt resistor to the +12v line and ground. Test away to make sure you have all your proper voltages.

      Let us know how you make out.

      this with 1 ohm 50 watt resistor to the +5v and 5 ohm 50 watt resistor to the +12v

      thanks for the attention guys. :thumbsup: i'm sourcing replacement parts now. might as well replace all if I can and maybe try to find a working PSU. I'll make another thread about Rebuilding a PSU