chaoticjelly
Kabuki Klasher
- Joined
- Sep 30, 2006
- Posts
- 128
Ok so I got this MVS 2-Slot for repair. The problem was that one of the colour was missing, it had already been diagnosed on this very board that was caused by a possibly faulty 74LS273 behind the Jamma connector. So I replaced this chip and the colour was working great again.
I then proceeded to remove the old rechargeable battery, did the 470 ohm resistor removal, and fit a CR2032 in socket.
I then removed and replaced ALL of the electrolytic capacitors with brand new ones.
There is a problem with the sound which was present before replacing the caps, the music on games will go all distorted and not sound quite right.
For example, Blazing Star will be okay, and then when you have chosen your character and it plays some music, it's distorted, the music is then distorted throughout the game. The same happens with my other cart. Samurai Shodown, when you get into the game, the music is all distorted.
The Neo Geo chime when you boot up is fine.
When I do a sound test, "RIGHT" sounds fine.. nice and loud.. "LEFT" is very very weak, unless you turn the volume on the TV up really high, you can't hear it at all. "CENTER" is fine.. nice and loud.
I've tried checking the output pins of the YM3016 with my Oscilloscope, but tbh I am not really sure what to set the scope to, as I haven't had it long (Tektronix 2246 100MHz).
My logic probe does not have audio output, so that's not a possibility.
The only thing I can see from inspecting the board is that a trace is broken near a 470 Ohm capacitor near to the Jamma edge. Then there is a piece of kynar patching to ground I think.. no idea what is going on there, but when I looked up on the service manual I think that Jamma pin was something to do with key mech or ???
Any ideas gratefully received. Once solved this will be a cracking 2-Slot
I then proceeded to remove the old rechargeable battery, did the 470 ohm resistor removal, and fit a CR2032 in socket.
I then removed and replaced ALL of the electrolytic capacitors with brand new ones.
There is a problem with the sound which was present before replacing the caps, the music on games will go all distorted and not sound quite right.
For example, Blazing Star will be okay, and then when you have chosen your character and it plays some music, it's distorted, the music is then distorted throughout the game. The same happens with my other cart. Samurai Shodown, when you get into the game, the music is all distorted.
The Neo Geo chime when you boot up is fine.
When I do a sound test, "RIGHT" sounds fine.. nice and loud.. "LEFT" is very very weak, unless you turn the volume on the TV up really high, you can't hear it at all. "CENTER" is fine.. nice and loud.
I've tried checking the output pins of the YM3016 with my Oscilloscope, but tbh I am not really sure what to set the scope to, as I haven't had it long (Tektronix 2246 100MHz).
My logic probe does not have audio output, so that's not a possibility.
The only thing I can see from inspecting the board is that a trace is broken near a 470 Ohm capacitor near to the Jamma edge. Then there is a piece of kynar patching to ground I think.. no idea what is going on there, but when I looked up on the service manual I think that Jamma pin was something to do with key mech or ???
Any ideas gratefully received. Once solved this will be a cracking 2-Slot