My Gottlieb Alien Star stopped booting off my original mpu so I bought a replacement Swemmer board. Upon installing the Swemmer the game booted and everything seemed good for about 2-3 minutes, then I heard a snap and my displays shut off and F3 fuse blew. I replaced the fuse and disconnected the player 2,3, and 4 displays and the game came back on with the player one and credits display. This seemed fine for about another 5 minutes and I heard another snap and the displays went out again and fuse blew. This time it was when I tried putting the key in the coin door lock which makes it seem like some kind of grounding issue.

On this game I replaced the big capacitor, the 3 cabinet rectifiers, and put a new power supply board in the game. My voltages we're all good and I did all of the recommended ground mods. I wasn't experiencing any display or grounding issues with my old mpu which leads me to think that it has something to do with the new Swemmer board.-i did the ground mod for this board upon installation. Any ideas of what I should try, or what could be causing this? My power supply board has good 5,8 and 12 volts but is missing the 42 and 60 volts for the displays due to them shorting out. Could it be a bad/shorted IC on the mpu or something else? Thanks!

Thank you! The capacitors all look correct from what I can see.

I'll check on the lane switch tomorrow. This issue happens in attract mode before starting a game.

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Thanks Ed. I have a brand new PS board in there now but my plan is to rebuild my original PS board and also get my MPU board working again. -the boards are all really clean (no battery damage on MPU) and I'd prefer to keep my originals in the game and use my repro boards for troubleshooting/spares.

thanks. It's a brand new power supply board (Gulf Pinball) and voltages were all in spec before i added the MPU which is why I suspected that as the potential issue since it's the only variable that's changed. my original PS is still good I just need to replace the toasty zener diode and put new caps in.

thanks. Yes that makes sense and agree that it likely isn't the MPU. It's likely just a coincidence and there may be a ground short somewhere that I need to track down. I haven't swapped displays yet. Displays were acting normal but something seems to be shorting my high power out.

This was it! thanks for the suggestion. I did use the shorter standoffs that came with the Gulf board, but it still sticks out too far and was just barely making contact with the ground strap which touches against the metal vent on the back of the head. -these cabinet heads are so shallow that there's just not much extra room. Sometimes it's the simple things like this that cause big problems!