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Cursed consolized MV1B take 2. Pop, smell, no more audio.

Kujako

Kujako

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So, making another pass at repairing a consolized systems based off a MV1B with a supergun designed by NeoJamma. Last pass resulted in an unresolved short to ground.

https://www.arcade-projects.com/thr...eo-mod-wire-running-from-opamp1-to-ic4.28884/

Piked up another MB1B board in a pile of parts and after cleaning and testing it seemed OK despite being an aliexpress special (the dumb stickers they put on the boards are a pain to remove). Wired everything up, and it all seemed OK until I tried to apply the 5v only audio modification with the same audio amp PCB shown in the previous shorted unit. Assembled and applied 5v power, everything works but no audio. Couldn't find the fault, so I tried unplugging the stereo audio and hooked up 12v along with 5v to see if I could get JAMMA audio. No video, heard a small pop, smelled the odor of frying electronics. Pulled everything apart, did a visual check and could find no issues, hooked it up to my standard workbench supergun and it all checks out and passes all diagnostics. But no audio. Swapped out the cartridge board with another (which may also be bad, see previous attempt) since that's where the Yamaha chip is and still no sound.

Anyone have any suggestions? Both on getting the sound working again and whatever the hell is going on with this supergun setup. I can't find any issues with how it's built and the designs are solid.

1715478182039.jpeg

1715478223068.jpeg
 
Wondering if the point of failure might be the audio amp PCB, but really can't spot any problems. Installed with C to pin A50 on the cartridge riser, B to the right most top pin on the OPAMP and A to the left top pin. Seems to be correct, but not 100% sure. It could have fried something I suppose. But first things first, need to revive this 1B. Still not sure where to start looking for the point of failure.
1715528903538.png


Edit: second guessing this theory since the board in question isn't powered. Not sure how it would feedback into the L, R and MIX inputs.
 
Last edited:
New-new theory. There's a short or issue somewhere in the superguns 12v lines. This setup uses a secondary PCB in the back of the unit to pass power in and AV out. The issues I've seen in all cases seem to happen when 12v is supplied. I can't find a short, but that's not saying there isn't one. So, removing/desoldering the wiring between the two halves and will add a 4 pin molex to the main unit and test from there. This is just to eliminate points of failure. If I can get the audio fixed and try again I'll just use two wires for 5v and ground.

1715609514999.jpeg

(wires removed)
 
Anyone know where to stick an audio probe to try and find where the point of failure is? These 1B's are kind of a pain to poke at due to how they're folded in half with the cart overlapping the majority of the main board. Test points on the bottom would be great...
 
I may need to solder in some wires to some points in order to use an audio probe... will give it a try this weekend. At the YM3016 and YM20610 I'm thinking (although the later is accessible from the back of the board).
 
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