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Thread: Neo Geo AES not booting, black screen, repair in progress

  1. #1
    . Bratwurst's Avatar
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    Neo Geo AES not booting, black screen, repair in progress

    Serial #020213, sticker underside says use Pro Pow only.

    Pic of the board: https://i.imgur.com/IWA8dvA.jpg

    System was given to a friend as-is years ago, and they have given it to me in an attempt to fix it. I presume it was fed the wrong power supply at some point. I'm hoping to get it working to give to another friend.

    Hooking up composite cable to Samsung LCD and a Sony 8" PVM, both black screen on power up with no game. Power supplied from bench top variable supply dialed to 5 volt but it never pulls more than 1.15-1.2 amps. Q2 PNP transistor B1135 positioned right after the switch is reading ok via diode checker. Voltage reading 4.75 volt immediately after D1 zener diode...

    Don't have a game on hand to test with, but will get one soon. I figured even without a game I'd get a color screen like blue, etc.

    Didn't see any damaged traces but I will give it a harder look again.

    Ran console with power for two minutes, measuring temperature with IR thermometer on all ICs. LS86 & LS05 next to the bios chip were getting warm up to 89F while everything else stayed 70F-72F (just a few degrees above room temperature.)

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    A game came in the mail, Samurai Spirits, still the same symptoms. Pulls 1.3 amps now instead of 1.15. Black screen, there is an audible buzz through the audio line on the PVM but not on the LCD. This buzz is present with or without the game btw.

    Planning on removing the bios to put in a socket and install the diagnostic rom, any recommendations?

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    What is the voltage coming in at pin 1 of the bios? Pin 2 is GRND.
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    Last edited by BIG BEAR; 03-14-2019 at 01:47 AM.
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    Getting 0.424 volts.

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    You need to be getting a reading of 5V there. Changing out the bios in favor of a diagnostic will do you no good until you have 5V hitting every component that requires it.
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    Quote Originally Posted by Bratwurst View Post
    Getting 0.424 volts.
    In case of 'PM BOX FULL ANXIETY' , E-MAIL ME

    bigbearatdreamamusement.net replace "at" with an "@"

    I'd like to sincerely THANK everybody that supported SHOCKbox over the (EST 2001) 8 - 9 years I did it.
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    LE GEEK SHOCKbox inserts

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    It was early enough I might have read the initial reading wrong- or touching solder to the vias has rectified something, because I'm now getting 5 volt on the bios. Double checked that for sure. Symptoms are unfortunately still the same.

    I measured the frequency of color burst clock and the bodge board output and they're both correct, 3.579Mhz and 24.167Mhz respectively.

    EDIT: I think it's the CXA1145, I'll post more later.
    Last edited by Bratwurst; 03-16-2019 at 02:13 PM.

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    Audio Out and C-Sync In of the CXA1145 were shorted, also wasn't getting RGB output. I took the chip out and I'm getting proper waveform on the audio line now (where pin 8 would be), and I see RGB activity where pins 2, 3 and 4 would be. Without a cartridge, only the color blue is active, with a cartridge, all 3 colors are doing their thing. So I am waiting on a new CXA chip to come in the mail and I believe that will fix it.

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    I have replaced the CXA1145. Sound now comes out properly from the rear port, but there's still no video. Csync input (pin 10) appears to be really low, 0.4v? Tracing it back to pin 126 of LSPC-A0, it appears to have a resistance of 5 ohms to ground. Is that normal? Because I have no other system to reference on hand.

    Previously, with the old CXA1145, pin 9 (Audio Out) was shorted to pin 10 but that has cleared up.

    Possible I was sold a bad CXA chip? It's certainly not outputting anything on the RGB channels (pins 21, 22 & 23.)
    Last edited by Bratwurst; 04-04-2019 at 12:42 PM.

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    I apologize for the persisted bump, but I thought this information may be helpful to others in the future. I was able to source a battery corroded MV1 board and determined that csync is normally 5 M ohms to ground pin on the LSPC-A0, and should NOT be 5 ohms as it was on the faulty AES. So I performed a transplant:





    The Neo Geo AES now works as it should. So my suspicion is someone plugged or unplugged a video cable into the system while it or the display was on, or there was a power surge- bridging the audio output and csync input of the CXA encoder. Which bled into the LSCP-A0 chip's csync output pin and eventually shorted it to ground.

    Video of the now fixed system in action:

    https://www.youtube.com/watch?v=leMB9AX9v-Q&

    Thanks to everyone who commented and offered suggestions.

  11. #11
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    congratz! Glad you figured it out and thanks for sharing.
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    In case of 'PM BOX FULL ANXIETY' , E-MAIL ME

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    I'd like to sincerely THANK everybody that supported SHOCKbox over the (EST 2001) 8 - 9 years I did it.
    is stocking the SHOCKbox right now!! They also have a huge library of SHOCKbox inserts for DL and or printing.
    LE GEEK SHOCKbox inserts

    I'm not protecting myself from you....I'M PROTECTING YOU FROM ME.
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