Power Supply Compatibility

[delti90]

Hopefully this isn't a dumb question, but I have a MVS-6-25 that I'm currently working on restoring. It has the green screen issue at bootup, and I tried popping unibios into the board, but it then wouldn't even get to the green screen (nor did unibios work on a fully working 1 slot board I have), so that leads me to think it could potentially be the power supply. I'm reading 5v at the jamma connector, but it dips to around 4.5v further away from the connector.

I'm still pretty new to NeoGeo so I don't know a lot about them. I'm looking at a new power supply and this seems to be the go to, and looks like it's the very similar to the one that's is currently in my cabinet. I'm ready to order it, but just came across this 200w psu. The connectors on it all look to be the same, albeit with some extras, I'm just wondering if it would work, or if I should just stick with the 150watt?

 

[Jasen Hicks]

When you say its dipping to 4.5V further away, where are you measuring it? Are you measuring it connected to the board or just free hanging?

When you plug the board in it becomes a load on the power supply and the voltage will droop. Its a natural phenomenon of electricity. Think of it like adding 500lbs to the back of your car instantly, the car has to work harder to maintain speed so the driver has to give it more gas for the same speed. The power supply is no different. When you install the board its acting like that 500lbs in the back of the car so the power supply voltage drops. Most power supplies have a 5V adjust knob on it. Connect your mulitmeter to the board 5V and GND points with it connected and powered up and adjust until it reaches 5V. If you cant get there, its probably a safe bet the power supply needs to be replaced.

 

[delti90]

When you say its dipping to 4.5V further away, where are you measuring it? Are you measuring it connected to the board or just free hanging?

When you plug the board in it becomes a load on the power supply and the voltage will droop. Its a natural phenomenon of electricity. Think of it like adding 500lbs to the back of your car instantly, the car has to work harder to maintain speed so the driver has to give it more gas for the same speed. The power supply is no different. When you install the board its acting like that 500lbs in the back of the car so the power supply voltage drops. Most power supplies have a 5V adjust knob on it. Connect your mulitmeter to the board 5V and GND points with it connected and powered up and adjust until it reaches 5V. If you cant get there, its probably a safe bet the power supply needs to be replaced.

Oddly enough my power supply does not have a 5v adjust knob. If I read right at the jamma connector it is pushing exactly 5v and the 12v line is pushing around 11.5. Basically, from what I've read on the forums, the furthest chip from the jamma connector should be getting no lower than 4.9, and when I am measuring a chip in the top right corner it is getting around 4.5. I just figured it might be worth replacing the power supply to see if that makes a difference since they're not very expensive and even if it doesn't it'll be good to have an extra.