Neo 25 Candy Cab - Left Speaker (or stereo) not working

[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.
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).

What am I missing and/or doing wrong?

 

[NoAffinity]

So, I did some more testing tonight, and the important conclusion is that the left speaker is actually working, but is barely audible. I can wire left speaker + or right speaker + (from JAMMA connector) to it, and it is the same result with either. Alternatively, if I wire left speaker + or right speaker + to the right speaker, the right speaker sounds normal.

The sound out of the left speaker isn't muffled or distorted or anything, more like producing at about 25% of normal. If I turn the speaker VR on the MV4 up all the way, the left speaker outputs as if it was at around 25% of max.

Thoughts? Blown speaker? Anything to test or check at the speaker itself at this point?

 

[daskrabs]

You probably need to recap the audio section. Common issue on multislots.

 

[Heinz]

It's actually not that uncommon on single slot boards either, if the caps have never been replaced it's time for replacement. Remember these things are nearly 30 years old!

 

[NoAffinity]

I was eyeballing the caps while i was tearing things down, and probably good to replace them, but I don't think that's the issue here. I replicated the issue on my test rig (jamma) as well, using a street fighter board to test. There seems to be an issue with the one speaker. I reflowed the connections on the speaker and I think it might have made a small improvement but still not great. Going to the electronics store on my lunch break to see if I can find some inexpensive replacements.

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[NoAffinity]

I found some replacement speakers online. Not an easy find by any means, but they looked right and are 4ohm 5 watt 3x5s. Got them in on friday, and they are an exact match to the originals. Problem solved, and with one pulled working spare now added to my spare parts pile.

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