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Thread: Neo 29 4 Slot (MV4FT3) Speaker Buzz/White Noise

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    icon19.gif Neo 29 4 Slot (MV4FT3) Speaker Buzz/White Noise

    I am working on cleaning up a Neo 29 4 Mini Marquee Type that I received recently. I was under the impression that these were wired for MVS, and would explain the weird behavior of a jamma board when the previous owner powered it up with one to show me it worked.

    So I just acquired a Neo 4 slot mobo and plugged it in for the first time. The aforementioned odd behavior is gone and the screen is fine, but I am getting a very loud audible "hiss/white noise" from the speakers.

    Even when the "speaker" fader on the mobo is turned all the way down I still get the loud white noise, and the volume of the game itself seems EXTREMELY amplified. Its very loud even when the fader is just barely turned up, I would say no more than 5-10%. I did not let it run for long because I was worried I was going to blow an amp or speaker because something wasn't the original wiring.

    So what do you guys think? Grounding issue? Could there be a fault on the 4 slot that Is causing it? Something else? Thanks so much guys!
    Last edited by jcmorris; 08-19-2017 at 08:55 AM.
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    Traced all wires and everything seems to be original. The Left and Right positives are going to L and 10 on the harness. And I even get the buzzing noise in the test menu. Im wondering if its not some sort of ground interference or other power interference from the PSU or another power source? Planning on removing the negatives from speakers and running a ground from one of the control panel grounds around the side to rule that out later today.

    Im also thinking it may be something in the audio section of the 4 slot I received but I have no way to test it against anything else (No other MVS wired cabinets, and only other neo mobo I have is a 1 slot Jamma. Everything else on the 4 slot functions flawlessly so I really don't want to recap the entire audio section if it doesn't need to be done.
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    Those volume sliders on MVS boards are notorious for going bad. I've got one on a 1F that has to be in the right spot not to cause hiss or other disturbances.


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    I had this problem with my 4 slot for the longest. Do you have an adapter to run Jamma boards in there? If the Jamma boards run fine it's the 4 slot. When I upgraded to a 6 slot, I didn't have the noise.

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    Quote Originally Posted by lachlan View Post
    Those volume sliders on MVS boards are notorious for going bad. I've got one on a 1F that has to be in the right spot not to cause hiss or other disturbances.
    Damn... Im assuming those sliders aren't easy to come by as replacement parts? My 1 slot has a working one but Id hate to sacrifice just to play trial and error.

    Quote Originally Posted by radiantsvgun View Post
    I had this problem with my 4 slot for the longest. Do you have an adapter to run Jamma boards in there? If the Jamma boards run fine it's the 4 slot. When I upgraded to a 6 slot, I didn't have the noise.
    I don't have an adapter, I guess I will have to buy one just to rule it out; Unfortunate because I don't plan on ever running anything besides a 4 slot in this cab. Eh, whats another 35$ Maybe someone will want it on here after Im done.
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    Quote Originally Posted by Xian Xi View Post
    Use fader lube on the slider to rejuvenate the carbon tracks. But the buzzing sounds more like a recap is needed on the mobo.
    I used fader lube, no change besides it being silky smooth now Guess Ill go ahead and order the proper caps and try that to rule it out.
    Last edited by jcmorris; 08-19-2017 at 08:32 AM.
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    Not sure why I didn't do this before (I guess the most obvious is the least obvious sometimes) , but I ruled out any funky wiring on the cab by just powering it up with no harness connected. There is no white noise or buzzing. So its definitely the 4 Slot.

    I took the Neo apart this morning to document all the caps and audio amp information. Here was my findings:

    Model: SNK NEO-MVH MV4FT3

    Audio Amp: HA13001

    Caps:
    Quantity Capacitance Voltage Width Height

    8x 470uf 16v 8mm 12mm
    2x 10uf 16v 5mm 10mm
    4x 22uf 16v 5mm 10mm
    4x 100uf 16v 6.5mm 10mm
    8x 4.7uf 25v 5mm 10mm
    2x 1uf 50v 5mm 10mm
    2x 220uf 16v 8.5mm 11mm

    These are all caps across both of the 2 motherboards.
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    I know this may be a simple suggestion, but have you plugged in a set of headphones into the 3.5mm headphone jack that is directly on the board to see if that part of the audio system has the same buzz?

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    Quote Originally Posted by NexusX View Post
    I know this may be a simple suggestion, but have you plugged in a set of headphones into the 3.5mm headphone jack that is directly on the board to see if that part of the audio system has the same buzz?
    I may be incorrect but I think mine uses a 4 pin headphone jack rather than the standard 3.5mm and I don't have the JST to hook up to the 4 pin connector on the motherboard.
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    Post some pics of the board of you have time. To my knowledge every 4 slot I have seen has two 3.5mm jacks on the bottom level PCB of the Mobo.
    Last edited by NexusX; 08-23-2017 at 05:42 PM.

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    Quote Originally Posted by NexusX View Post
    Post some pics of the board of you have time. To my knowledge every 4 slot I have seen has two 3.5mm jacks on the bottom level PCB of the Mobo.
    The retard selling this has the same model, or one thats similar: (mine is a MV4FT3 this is a MV4FT2)
    http://www.ebay.com/itm/NEO-GEO-MVS-...-/311750555236
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    Quote Originally Posted by jcmorris View Post
    The retard selling this has the same model, or one thats similar: (mine is a MV4FT3 this is a MV4FT2)
    http://www.ebay.com/itm/NEO-GEO-MVS-...-/311750555236
    I am looking for the pinout list on the 4 pin stereo plug. I will tell you the pinout if I find it. If I find it at least you can spend the $3 in parts and wire up a 3.5mm to it if one is not located on the board.

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    Quote Originally Posted by NexusX View Post
    I am looking for the pinout list on the 4 pin stereo plug. I will tell you the pinout if I find it. If I find it at least you can spend the $3 in parts and wire up a 3.5mm to it if one is not located on the board.
    Please stop posting nonsense when you have no idea WTF you are talking about.
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    Im finally getting the Caps delivered today so Ill find out later if thats the issue or not. Time to break in the new Hakko 303! Fingers crossed...will update later and hopefully put this to rest.
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    Quote Originally Posted by madman View Post
    Please stop posting nonsense when you have no idea WTF you are talking about.
    Then please add in the "proper" information when you post that someone's info is inaccurate. Or do you not have an answer for the man yourself?

    In regards to the OP I am seeing if I can find the user manual online for that exact model of board to see if there are (if any) other options for connecting a 3.5mm jack to. Good luck on the cap kit btw.
    Last edited by NexusX; 08-24-2017 at 09:08 AM.

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    Quote Originally Posted by NexusX View Post
    Then please add in the "proper" information when you post that someone's info is inaccurate. Or do you not have an answer for the man yourself?
    So if someone doesn't post a correct answer, you're allowed to post total nonsense and mislead people? The 4 pin stereo connector pinout is widely available using a SEARCH. FUNCTION. However, to stop the spread of total bullshit from a n00b, the 2 middle pins are grounds, 1 and 4 are + for the L and R speakers respectively. He can also follow the traces off the MVS edge and wire up another connector that way as a different option.

    Edit: On second thought, double check that by tracing the pins, as that's the pinout on the 1-slots. It might be different on your 4 slot, I am not certain.
    Last edited by madman; 08-24-2017 at 09:01 PM.
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    Quote Originally Posted by madman View Post
    So if someone doesn't post a correct answer, you're allowed to post total nonsense and mislead people? The 4 pin stereo connector pinout is widely available using a SEARCH. FUNCTION. However, to stop the spread of total bullshit from a n00b, the 2 middle pins are grounds, 1 and 4 are + for the L and R speakers respectively. He can also follow the traces off the MVS edge and wire up another connector that way as a different option.
    Then clearly you know the pinout (Hallelujah a real useful and informative post) . What information that I listed was incorrect? So that means you can wire up a 3.5 to it right? So how does that negate the method of troubleshooting the sound issue? Just because I didn't know the pinout offhand?

    You are welcome to shoot back another public response to have the last word on here if you desire but out of respect for the OP and the thread just start a flame thread about what ever you disapprove of about me in the flame section. Or hell... shoot me a PM if you have something more articulate to say in a conversation.

    OP I wish you luck on your repairs. Now that you have that cap kit and the pinout from madman here I hope you are able to narrow down your problem.

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    recapped both boards, as well as replaced the sound amp. No change
    Taito Egret II (x2) , Konami Windy (x2) , SNK SC19-4, SNK Neo 29, Konami Domy Jr

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    Quote Originally Posted by NexusX View Post
    Then clearly you know the pinout (Hallelujah a real useful and informative post) . What information that I listed was incorrect? So that means you can wire up a 3.5 to it right? So how does that negate the method of troubleshooting the sound issue? Just because I didn't know the pinout offhand?

    You are welcome to shoot back another public response to have the last word on here if you desire but out of respect for the OP and the thread just start a flame thread about what ever you disapprove of about me in the flame section. Or hell... shoot me a PM if you have something more articulate to say in a conversation.

    OP I wish you luck on your repairs. Now that you have that cap kit and the pinout from madman here I hope you are able to narrow down your problem.
    Cry me a river.





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    So I ruled a few other things out today. I wired a new power cord with ground and connected to the ground post on the back of the unit.

    I also wired up another 4ohm speaker to the left (and right) channel and the same "PPSSSSSSSHHHHHHHH", "Your amp volume is turned way the fuck up" sort of noise was present on the other speaker. So that rules out the actual speakers themselves.

    I then wired up the same speaker to the left channel o the 4pin JST headphone jack, the PSSSSHHHH noise is NOT PRESENT on the headphone jack whatsoever. The speaker (even when fader was turned all the way up) was very low but to be expected for the headphone output I guess. Im not really sure what this would suggest? Anyone have a clue? Is there a particular IC in the audio circuit that I need to look for or probe/ oscilloscope?
    Last edited by jcmorris; 08-26-2017 at 07:01 PM.
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    Well glad you wired up the 3.5mm jack pins. That looks like it means that it is
    1. Your cabinet speaker wiring and/or speakers and NOT the board itself

    Or

    2. Something on the board that is post sound processing circuitry to the edge connector part of the board.

    Have you tested all your sound on the cabinet speakers or did you use headphones or another set of speakers on the 3.5 jack pinout test?

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    Quote Originally Posted by jcmorris View Post
    So I ruled a few other things out today. I wired a new power cord with ground and connected to the ground post on the back of the unit.

    I also wired up another 4ohm speaker to the left (and right) channel and the same "PPSSSSSSSHHHHHHHH", "Your amp volume is turned way the fuck up" sort of noise was present on the other speaker. So that rules out the actual speakers themselves.

    I then wired up the same speaker to the left channel o the 4pin JST headphone jack, the PSSSSHHHH noise is NOT PRESENT on the headphone jack whatsoever. The speaker (even when fader was turned all the way up) was very low but to be expected for the headphone output I guess. Im not really sure what this would suggest? Anyone have a clue? Is there a particular IC in the audio circuit that I need to look for or probe/ oscilloscope?
    I'm telling you man, give that big red adapter a shot. The 4 slot I had in my neo candy was giving me the exact problems and it had been freshly recapped. I sold the 4 slot to a friend and it gives him no problems in his big red. I don't know if a particular model of 4 slot isn't 100% compatible with these cabs, but the 2 slot and 6 slot I tested in mine only gives that feedback once the cabinet is powered on and once the NG logo comes it, it goes away. With a jamma adapter, you can 100% rule out anything but the 4 slot.

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    Quote Originally Posted by radiantsvgun View Post
    I'm telling you man, give that big red adapter a shot. The 4 slot I had in my neo candy was giving me the exact problems and it had been freshly recapped. I sold the 4 slot to a friend and it gives him no problems in his big red. I don't know if a particular model of 4 slot isn't 100% compatible with these cabs, but the 2 slot and 6 slot I tested in mine only gives that feedback once the cabinet is powered on and once the NG logo comes it, it goes away. With a jamma adapter, you can 100% rule out anything but the 4 slot.
    My concern is that my speakers appear to be wired in parallel , not series like the adapter calls for. It specifically states in all documentation that it is not meant to be used with cabs wired in parallel. Do you have any experience with it? Was the 4 slot you had an FT3? I wouldn't be surprised if you were right about it being some revisions that are not compatible, as there were quite a few and maybe this was meant for a Big Red...
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    Quote Originally Posted by jcmorris View Post
    My concern is that my speakers appear to be wired in parallel , not series like the adapter calls for. It specifically states in all documentation that it is not meant to be used with cabs wired in parallel. Do you have any experience with it? Was the 4 slot you had an FT3? I wouldn't be surprised if you were right about it being some revisions that are not compatible, as there were quite a few and maybe this was meant for a Big Red...
    Mine was a MV4F. I did ask james about the adapter and neo candies and he assured me it would be fine. I don't use it as often as I have more options, but it works great for me. Our cabs are basically the same with yours having a larger monitor. The sound baffled me for months as if I used the 4 slot in another cab with a jamma adapter it worked fine in mono.

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