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brendan1495

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Hi all, Just a quick question I have an MVS in my Arcade cab and have just done the stereo mod which entailed taking out a couple of resistors and soldering in a small PCB I the connected to phono plugs. When I connected it up to an amp I get hardly any volume from the stereo speakers, I can hear it but very low. If I adjust the volume pot on the board it just turns up the cab speaker, I presumed this would be disabled after I removed the resistors. Do I need to do the 5v mod to disable the cab speaker or is there another way. Had a look through the forum and cant find anything related to this issue.

Any help would be appreciated.

Thanks

Brendan
 

nam9

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Which tutorial are you using? And which amp (small PCB).
 

SVM

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It seems like something is wired wrong etc. Could you take some good photos of you work, please?

And no, you don't need a 5V mod for the stereo mod.
 

brendan1495

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Hi pictures below the only ones I haven't shown are the phono plugs but thats just left right and ground.
 

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SVM

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Please check you resistor values again. For example R5 and R6 need 10kΩ and you've installed 1kΩ ...

Further R12 and R14 need 10kΩ, too (it seems like you have installed 10Ω). :)
 
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nam9

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Safe bet @SVM has caught the issue if those values are out.
The mod you have preformed just taps Stereo. It doesn't disable the rest of the sound system.

What is your use case? I am reading that you have this installed in a cab with both mono speakers and stereo speakers attached.
In that case you will need to be able to disable the amplified audio somehow.
Preforming the 5v mod is not a good idea as you will still be applying 12v to the board (via Jamma connector).
According to @XianXi on JNX that will also give you scrambled video.

You can ask in the Neo Geo 1X Stereo Mod thread how people disabled their Mono circuits.
Easiest solution could be to just cut the traces behind the Jamma pins 10/L (traces in white)?

Untitled.jpg
 
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brendan1495

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Thanks for your quick replies I will check my resistor values and remove/ replace as necessary also will see how other people have disabled there mono circuits.

Thanks a lot, will let you know how it goes
 

XianXi

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In order to get true stereo the resistors need to be removed but in doing so cancels the mixing of the 3 channels so there’s only going to be a hum from the cab speaker that’s wired to the harness.

You could always just lift the power pin to the amp or cut the trace to it or if you aren’t using coin counters just disable the 12v line all together on the PCB with tape.
 

brendan1495

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Hi, I have already removed the resistors if I disable the 12v line on the PCB with tape, will this cut power to the mono circuit and allow the stereo speakers to work. This idea sounds the least destructive, I would hate to disable the mono circuit only to find my stereo is still not working.
In order to get true stereo the resistors need to be removed but in doing so cancels the mixing of the 3 channels so there’s only going to be a hum from the cab speaker that’s wired to the harness.

You could always just lift the power pin to the amp or cut the trace to it or if you aren’t using coin counters just disable the 12v line all together on the PCB with tape.

Thanks

Brendan
 

XianXi

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Well, right now the mono circuit is disabled since the resistors are removed.
 

brendan1495

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Well, right now the mono circuit is disabled since the resistors are removed.
Hi,I have removed R36 and R37 but the audio is still coming out of the cab speaker. I will disable the 12v tonight when I get home from work and see if that makes any difference to the output.

Thanks for your help.

Brendan
 

brendan1495

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Well, right now the mono circuit is disabled since the resistors are removed.
Hi,I have removed R36 and R37 but the audio is still coming out of the cab speaker. I will disable the 12v tonight when I get home from work and see if that makes any difference to the output.
Thanks for your help.

Brendan
Looks like its my board, put a simple one I made (perf board) for a consolized MVS a couple of years ago and it works fine will need to have a good look at the boards and see were ive gone wrong. Thanks for all your help

Brendan
 

brendan1495

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Just another quick question been looking at my board and checking everything I have uses 4.7uf 50v caps instead of 4.7uf 16v caps would that make any difference ?
 

Sp33dFr34k

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Just another quick question been looking at my board and checking everything I have uses 4.7uf 50v caps instead of 4.7uf 16v caps would that make any difference ?
No, a higher voltage would be okay to use.
 

jassin000

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Anyone got a nice OSH Park/Digikey BoM for this simple design?
fz-1b-stereo-circuit-sm2.jpg
 
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