MVS Sound/Power Issue

doaal

Mr. Big's Thug
Joined
May 7, 2018
Posts
209
Hi all,

Recently I bought my first MVS board (MV1ACH) on the cheap. The owner tried to do a stereo mod and had the watchdog colour issue--swapping the stock BIOS to UniBIOS fixed this. Hey, a working Neo! Since he cut the 12v trace I assumed all I had to do was reattach it and I'd have sound, except when I did, the board wouldn't power on. I get a small flicker from my power supply and then it shuts down.

I removed the copper wire I used to connect the trace and the Neo board powers on again as normal. I'm assuming some of the other work the past owner did on the board is causing some kind of issue with the 12v? I've included a picture of the part of the board where the work has been done, along with the cut 12v trace. Aside from what's in these pictures, he installed a battery holder but that's pretty idiotproof.

Any help with this is appreciated.unnamed.jpgcapture.jpg
 

ack

Ninja Combat Warrior
15 Year Member
Joined
Apr 9, 2009
Posts
538
That red wire in your first picture is connecting 5V to 12V rail. I assume the guy was trying to do the 5V audio mod which is to power the audio amp off the 5V rail instead of the 12V one. By reconnecting the 12V rail you are causing a bridge between the 2 voltages, which is bad.
 

doaal

Mr. Big's Thug
Joined
May 7, 2018
Posts
209
One thing I did try after taking the picture was removing the wire. Definitely safer, but didn't fix the issue.

Tomorrow I'm grabbing some sandpaper and desolder braid so I can try making a very clean retrace, just to be on the safe side.
 

Neo Alec

Ned's Ninja Academy Dropout
20 Year Member
Joined
Dec 7, 2000
Posts
11,925
Look up the 5v Only Mod instructions on Jamma Nation X and make sure you reverse all the steps that have been done.
 

doaal

Mr. Big's Thug
Joined
May 7, 2018
Posts
209
The only thing I haven't been able to reverse is the cut between the sound amp and 12v. But testing the amp's pads with the rest of the board I seem to be getting continuity. Are there specific resistors/spots I should test as I try to repair the trace?

I'm not the best with electronics repair so bear with me.
 

doaal

Mr. Big's Thug
Joined
May 7, 2018
Posts
209
I've fixed the problem and she boots! But the only sound I'm getting is the coin insert. This may be a capacitor issue?
 
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