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  • Green gun seems to keep firing

    Hey All,
    Anyone here know why this is happening and what the fix would be?
    My google-fu is failing me.

    Thanks!
    Click image for larger version

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  • #2
    Spark gap on the green cathode has become partially conductive. If this is the case, removing the gap is easy and quick before checking other things in the green circuit. Mentioning the monitor model and posting a pic of the neckboard would help.

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    • #3
      Thanks for the reply! Iíll be in a position to pull it apart on the weekend and confirm, this is in a Daytona USA.


      Sent from my iPhone using Tapatalk

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      • #4
        Ok it is a nanao 05a0036261 chassis
        And a Toshiba A68KJU96X Tube

        Picture below





        TIA


        Sent from my iPhone using Tapatalk

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        • #5
          It's a Nanao MS8-29. Desolder this component on the CRT board (lifting one leg would be enough):

          https://imgur.com/QEvFqVt

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          • #6
            Thanks for the advise! Before I do it can you explain what this does exactly or share any links that may educate me?

            TIA


            Sent from my iPhone using Tapatalk

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            • #7
              Your red/blue plug horizontal yoke is in the wrong section..Need to line up it next to the vertical plug.

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              • #8
                Looks like I have a few more caps and resistors




                Sent from my iPhone using Tapatalk

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                • #9
                  Those are not relevant. Desolder the brown spark gap closest to the blue cap. It's for protection. In case of a flashover inside the tube it attracts the spark that would otherwise damage the cathode and discharges it to ground. If it's defective it could leak to ground and that would explain the excess of green (a complete short across the cathode and ground would give a full green screen). So this is easy to check as a first step. If the green streak is still there you'll have to troubleshoot other components in the green circuit (diodes and transistors) and that's more complicated.

                  Similar problem on a MS9:
                  https://forum.arcadeotaku.com/viewto...31401&p=439663

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                  • #10
                    Originally posted by dragonlee View Post
                    Your red/blue plug horizontal yoke is in the wrong section..Need to line up it next to the vertical plug.
                    Genuine questions: given there are visibly two whole yoke connectors on the board, why the double? Are they just vertical mirrors, for a complete 4-in-line plug that hasn't been snapped in half? If so, why does matter which way around the plugs are, as long as the image looks right (and of course, you never mix vertical and horizontal)?

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                    • #11
                      Originally posted by buttersoft View Post
                      Genuine questions: given there are visibly two whole yoke connectors on the board, why the double? Are they just vertical mirrors, for a complete 4-in-line plug that hasn't been snapped in half? If so, why does matter which way around the plugs are, as long as the image looks right (and of course, you never mix vertical and horizontal)?
                      vertical yoke plugged in 15k and horizontal plugged in 24K.
                      Are you sure he has taken the right picture image ?
                      Have you ever worked on Nanao Chassis before [MENTION=16024]buttersoft[/MENTION] ?

                      Comment


                      • #12
                        Originally posted by dragonlee View Post
                        vertical yoke plugged in 15k and horizontal plugged in 24K.
                        Are you sure he has taken the right picture image ?
                        Have you ever worked on Nanao Chassis before [MENTION=16024]buttersoft[/MENTION] ?
                        Only older stuff, i'm really only working on the stuff i have. And paying attention to other threads so i can learn, of course

                        Cheers for the reply. I didn't know anything worked that way, i would have thought it was all handled elsewhere and then just pushed out through the same yoke connector.

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                        • #13
                          Nothing wrong with the yoke connectors.

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                          • #14
                            Hey Joe ,

                            Mate if that was a problem on the neck board it would be displayed as the screen fully saturated in Green and retrace lines, with Blue and Red only visible in the background, so the problem is not neck board related.
                            The fact the green is in the correct color bar means the signal going into the chassis and through the color amp module on the chassis is being over amplified.
                            The amplifier section is clamped to 5.1v coming in but you should only be getting around 3.0vdc on each color coming in to the chassis input connector, if the input voltage is higher than 4.0v the problem is coming from one of the color drives on the bottom layer of the game board ( easy to verify just swap the game board to the other side and see if the problem follows ) , if you swap the board and voltage stays above 4.0v then swap the filter board that connects to the front of the game board stack ( the filter board has resistor/capacitor network for each output, when the resistor inside goes open circuit which holds the output below 4.0v you will get this over driving problem) , when the capacitor shorts you will read 5.0v from the effected color.

                            If all voltages compared to each on each color are about the same then the problem is with the color amp module on the chassis, what ever you find the fix is simple just drop it in and I'll see if I can sort it out while you wait.

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