Neo 25 Candy - Left speaker (or stereo?) not working

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Neo 25 Candy - Left speaker (or stereo?) not working

Post by NoAffinity »

So I've got another challenge with this cab. The current situation is the left speaker isn't working (testing both speakers from the test menu).

My 4-slot board is NEO-MVH MV4-FT3

How I got to this point:

1) Left speaker was working initially with no right speaker.
2) Found the right speaker wire (at pin 10) cut about 2" away from the JAMMA connector. The end that had been cut was then twisted onto the pin 11 (AUDIO + (mono)) at the jamma connector. The left speaker + wire was connected normally to pin L (Speaker + (L)).
3) I spliced the two cut pieces back together, with a soldered and heat-shrinked connection, making a good connection at pin 10 from the right speaker. Good connection still at Pin L from left speaker.
4) I then tested and am getting the right speaker working but not the left.
5) I checked the wiring at the speakers, and found (+) and (-) reversed on the left speaker terminals.
6) I corrected the wiring at the left speaker terminals, but got no improvement.
7) I tested continuity across the speakers, and am getting continuity across all four terminals.
8) I tested continuity from the in-line connector within the cabinet, and am getting continuity from the right speaker wire to pin 10, from left speaker wire to pin L, and from (-) to pin 27 (GND). Pin 10, pin L and pin 27 are also all continuous at the JAMMA harness (and presumably at the in-line connector as well).
9) I poked around in the soft dip settings, and found no setting to enable stereo output.
10) I have an 8-switch dip bank. Switch 7 is set to on and enables free play. The hard dip display in the test menu corroborates that free play is on, but only shows 4 settings in that menu (not 8). I tested each dip set to on, individually, and got no improvement.

What am I missing and/or doing wrong?
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Re: Neo 25 Candy - Left speaker (or stereo?) not working

Post by Flinnster »

I don't think the dips affect audio at all do they on the MVS bios? Just the test menu that allows you to test LEFT/RIGHT/CENTER.
Here's the settings, you'll see most of the DIP switches are just for comms ID on the motherboard (so only useful for link-up):
http://www.arcaderestoration.com/gamedi ... o-Geo.aspx

For the wiring, I've had this one on hotlink for a while:

https://www.google.co.uk/url?sa=t&rct=j ... z5XlxZLH7Q

Might be worth checking what Audio Ground is doing on Pin M? Or is it the test switch if your cab is MVS wired?
Certainly what you're saying about L/10 and ground seem fine to me. Perhaps try another ground - pin 28 or 1 for instance / connecting those to pin 27.
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Re: Neo 25 Candy - Left speaker (or stereo?) not working

Post by Flinnster »

Also... maybe something in the soft dips (you need a game installed):

http://www.neo-geo.com/forums/showthrea ... MVS-4-SLot
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Re: Neo 25 Candy - Left speaker (or stereo?) not working

Post by NoAffinity »

Thanks, Finnster. I'm pretty sure there is no setting on the 4-slots to change between stereo/mono, but will check again. The AO summary of MVS boards shows only 2-slot boards have that option, and the end of that thread you linked, the OP said he didn't find it in his test menu. But fingers crossed, maybe I overlooked something.

The only other things I can think of is maybe voltage needing to be dialed up a bit, to drive the audio. Or, heaven forbid, some issue with the board. Will try swapping L and R + wires between speakers tonight, too.

If anybody else has any thoughts, please post up. :)
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Re: Neo 25 Candy - Left speaker (or stereo?) not working

Post by NoAffinity »

Okay, so did some deeper testing, and removed the back panel lock so I could get to things easier.

Conclusions:
Left speaker is actually playing audio, but very faintly. I would say it is about at 25% of the right speaker. If I turn the speaker VR all the way up, the left speaker is acceptably audible.
I tested both the Speaker L and Speaker R lines on the left speaker, with the right speaker not connected and get the same result. I tested both L and R lines on the right speaker with the left speaker not connected, and it plays audio fine (normal levels), with either signal wire connected.

I also checked the grounds back to the single ground pin that they are grounded to, at the JAMMA harness, and continuity strong. Continuity is strong from all terminals back to all points Pin L, Pin 10 and GND.

So, is the left speaker blown?
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Re: Neo 25 Candy - Left speaker (or stereo?) not working

Post by nem »

NoAffinity wrote:I tested both L and R lines on the right speaker with the left speaker not connected, and it plays audio fine (normal levels)

[snip]

So, is the left speaker blown?
Yes.
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Re: Neo 25 Candy - Left speaker (or stereo?) not working

Post by NoAffinity »

nem wrote:
NoAffinity wrote:I tested both L and R lines on the right speaker with the left speaker not connected, and it plays audio fine (normal levels)

[snip]

So, is the left speaker blown?
Yes.
Thanks, nem! I pulled the speaker out of the cab and tested on my test rig. Same result...very low audio. I re-flowed the connections and it seemed to make a small improvement but not great. With the speaker out of the cab, I could see light coming through areas around the perimeter of the cone. I expect this is at least partially the cause...the cone is just deteriorating over time. Going to the electronics store today to see if I can find some inexpensive replacements.
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Re: Neo 25 Candy - Left speaker (or stereo?) not working

Post by NoAffinity »

Well, searching high and low online, I had almost given up hope. I decided to give this a try before running to the local electronics store, and am probably glad I did since a replacement for these old oval 4 ohm speakers seems almost non-existent.

Almost...

I found these little guys, and for super cheap too:

https://www.sciplus.com/p/OVAL-SPEAKER_50767

Fingers crossed that they will work okay. If not, then I think my only option is a 3" square speaker which will simply only get screwed down to 2 of the 4 speaker posts in the cab topper. It's not like you can see the speaker inside the topper, but the OCD in me says if it can be done right then do it right! :lol: :cry:
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Re: Neo 25 Candy - Left speaker (or stereo?) not working

Post by NoAffinity »

Quick update here. Those speakers are an exact replacement. I'm now gaming in stereo...and have a pulled working spare in the stockpile. :awe:
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