Neo Geo MV-1 with two issues

kruuth

Member
Joined
May 21, 2009
Messages
645
Reaction score
1
Location
Georgia
I've got a Neo*Geo MV1 with two problems. First, when I go into the test mode it thinks that the P2 Left is constantly being pressed. It's not. I haven't even wired up controller 2 yet.

The other problem is a little more complicated. I ordered a jamma extender from twistedquarter here: http://www.twistedquarter.com/index.php?main_page=product_info&cPath=177_237&products_id=1225

When I don't use the extender, everything looks fine. When I use the extender the screen looks like this:



Any suggestions on how to remedy this? I've not used an extender and it's clear not all the pins are connected.
 
I think the extenders don't have -5vdc wired, at least mine doesn't and thus my Namco Classics 2 board won't work with it, so if the board needs it you're going to have to add that wire to get it to work.
 
Neo Geo doesn't use -5v.

Your JAMMA extender is dropping too much voltage. Check the voltage at the board with your multimeter.

For P2, check the trace from the JAMMA edge connector back through the resistor packs that hold the signal high. You have a bad resistor pack, bad trace, or a bad Neo chipset chip.
 
Yeah I checked the voltage...looks like I'm pushing around 11.6v at the harness.
 
Hey channelmanic, how hard is it to fix something like that?
 
Don't measure the +12v, it's only used for the audio amp section of the board.

You need to be concerned about the +5v. Measure it. You should replace the wires for the ground and the +5v connections on the JAMMA extender as they aren't beefy enough and you're getting too much voltage drop.

As for the input issue, it depends on which is the problem. If it were me, I'd tackle it this way:

  1. With the power off, unplug the game board and check the input pin on the JAMMA harness and make sure it has NO continuity to ground.
  2. If the input pin has no continuity to ground then eyeball the traces going back from the JAMMA connector and see if you find any gouges or other physical damage.
  3. Check the resistor pack to see if the resistance from that pin to +5 and see if it is similar to the pins next to it. You may have a bad resistor pack.
  4. Check the traces from the resistor pack to the Neo chipset chip.
 
I think I'm pulling 5v...I'm going to test with a different multimeter. What's the min/max it should be? Sorry, I haven't played much with neo geo units.
 
Nope, checked the resistance on the edge connector. Nothing wrong there.
 
Back
Top Bottom