· 01-13-2025 ·
MARIO BROS
OWNER : PHILIP C.
SYMPTOMS
| NO SOUND |
Here is a Nintendo Mario Bros. PCB set that has been sent in because it has no sound. In a note sent with the PCB, it says the sounds don’t sound correct, but there is no audio at all.
Board looks to be in great condition except for one area that is torched.
Here is the problem area. I don’t know who tried to repair this, but they put the incorrect value resistor here. It is a larger wattage resistor than is needed, and it is also a 10k ohm resistor instead of a 1k ohm that is needed.
They also failed to fully connect it. The vias were ripped out, so on the left side, it is only connected to that red wire that they added. The red wire heads up to the audio out pin on the edge connector. But that left side of the resistor is also supposed to be connected to the center pin of that Q10 transistor. That is where the audio comes out and it is not connected to the resistor.
This need to be redone properly.
Cleaned up, blown traces are patched, 1k resistor installed and secured nicely thru the vias. Everything is connected as it should be.
I used a little too much acetone to clean up some leftover black soot after I installed the resistor so the colored indicator bands on the resistor dissolved. But it is a 1k resistor.
Powered on….all sounds are 100% working now.
The owner of this board has also said the batteries don’t save the high score tables and wanted me to try and fix it. I wasn’t aware at the time that most Nintendo boards of this era don’t save high scores with the batteries. The batteries are only there to save the financial statistics.
But the info is stored on the RAM at 7A. Tried to see how an NVRAM would do in that location.
Pulled 6116 RAM at 7A – Installed Socket – Installed NVRAM
No change. High scores still don’t save.
Pulled 6116 RAM at 7B just for shits and giggles – Installed Socket – Installed NVRAM
No change.
Did a quick search and came to find out that the game program initializes the high score table every time the game is powered on. So there is no escaping it with just an NVRAM. No matter what is in the high score section saved in RAM, the program is going to wipe it right on bootup.
But, out of pure coincidence… It just so happens 5 days prior to this repair, an arcade legend, Mark Spaeth, just wrote a hack to fix this very issue. And also includes the ability to preserve the FREE PLAY setting, which also resets.
On KLOV he posted the code that needs to be patched. Here is part of it.
So I patched the appropriate ROMs at 7C and 7E, burned them up, plugged them in with the NVRAM loaded at 7A. And its working perfectly!
High scores are saving and free play is persistent. Everything looks good.
To clear the high scores, you can hold P1 and P2 start on power up and that will wipe the scores.
To keep it on free play, just turn dip switches 3 and 4 to the ON position.
Thank you Mr. Spaeth, the owner of this board will be very happy!
Been testing for a while now and everything is rock solid.
Removed battery holder.
Board is fixed!
Repair required :
(1) 1k ohm Resistor
(2) 24-Pin Sockets
(1) 2732 EPROM
(1) 2764 EPROM
(1) 6116 NVRAM Module
…and some burned up trace repair
CobraKai's Arcade Repair 