Neo Geo 4 slot just died...please help

FlashbackArcade

Well-known member
Joined
Apr 24, 2011
Messages
1,647
Reaction score
143
Location
Selden, New York
OK, today I go to turn my NeoGeo on and it just freezes. Now I can't get it to do anything else. Tried different carts in all 4 slots, unplugged the machine and tried to power up an hour later, etc but got nothing. Anyone have any idea what is going on with my machine? I have attached a picture and would greatlt appreciate any help on this one.
 
Last edited:
Power Supply first...

After that, I'd pull the boardset apart and check for battery leakage.
 
NeoGeo Help

Ok, I measured the voltages coming out of the power supply from the 9 pin connector:

Here's what I got:

Pins 1, 2, and 3 +4.99 voltage output (supposed to be +5.00)

Pins 4, 5, and 6 Ground pins

Pin 7 -4.93 voltage output (supposed to be -5.00)

Pin 8 +10.63 voltage (supposed to be +12.00)

Pin 9 Empty


Does this mean that the power supply is dead? Can I make an adjustment to it or am I close enough to assume that the board is the problem?

Thanks to all of you trying to help me with this!
 
Both my neos have cheap Peter Chow P/S and they have a knob that adjusts the voltage. If yours doesn't have a knob, get a replacement P/S. My Zero Gunner would loose all video after about a minute and it turned out to be a out of adjustment P/S.
 
Test the PSU with the MVS board connected to it. And, take your MM readings at the MVS edge connector, where the MVS harness meats the board. The +5V line is the important line to meter. It ought to be between +5.00~+5.10 volts. I aim for +5.05V. Do NOT go over +5.25V, when adjusting the PSU power to the board. It's bad for the chips on the board. But, the board ought to power up OK if the power is somewhere near +5.0V.

SSSooo, also find the NIMH battery on your board, remove it, and look for signs of leakage and corrosion. On the 4 slot MVS boards, VIDEO and CALENDAR lines run near the battery. A leaky battery can mess these lines up causing a bunch of garbage and greenness to appear on screen. The battery should be on the bottom board, on the right side, near the front of the board connector

MV-4FallopenSm.jpg
 
Last edited:
Not only the video and calendar lines but also the /CE and /OE lines for the Backup RAM. If those go south then the Backup RAM will spuriously output garbage on the main CPU data bus which causes the board to simply never boot.
 
Back
Top Bottom