neo geo help repair

[raylyd]

hi i have got 2 neo geos that needs a repairing ram chips i need some place to find them that takes paypal can a neo geo boot to the bios with out a game cart please let me know thanks as neo geo stuff is new to me
thanks

[Blur2040]

Contact member channelmaniac here or on neo-geo.com.

I know he tends to specialize in arcade boards...but AES is vaguely in that realm, so he might be able to help.

[Twimfy]

An AES will not do anything without a cart unless you hold all four buttons down on the controller in which case it will load the memory card manager.

[lherre]

I have one AES without sound (strange static sound when you boot a game in the screen or in the headphone output), I tried to test the sound chip without any result. Any ideas??

[channelmaniac]

Most likely a dirty cart/slot or a bad trace coming off the cartridge slot to the sound section of the board.

Clean the cartridge and the slot first.

[channelmaniac]

raylyd ended up having AES units. He PMed me to let me know he fixed a couple of broken traces and now gets a blue screen on power-up. This is good as that means it is now passing self tests.

Here's a tidbit from my repair logs:

The AES is different than the MVS in that it does not display error messages on the screen if there are hardware problems. To diagnose problems, boot the system without a cartridge installed. The screen will turn different colors depending on the errors.

Blue = All tests passed
Red = WorkRAM error ($100000 region)
Green = PaletteRAM error ($400000 region)
Yellow = VideoRAM error
Pink = Bios selfcheck error ($C00000 region)
Cyan = Memory card error

The AES tests will only test the memory card if it is inserted and it is blank. It does NOT test the Z80 or other parts of the sound subsystem.

Raymond

[lherre]

Most likely a dirty cart/slot or a bad trace coming off the cartridge slot to the sound section of the board.

Clean the cartridge and the slot first.

I tested this, I have 3 neogeos and only one hasn't sound (with the same cartridges).

[l_oliveira]

raylyd ended up having AES units. He PMed me to let me know he fixed a couple of broken traces and now gets a blue screen on power-up. This is good as that means it is now passing self tests.

Here's a tidbit from my repair logs:

The AES is different than the MVS in that it does not display error messages on the screen if there are hardware problems. To diagnose problems, boot the system without a cartridge installed. The screen will turn different colors depending on the errors.

Blue = All tests passed
Red = WorkRAM error ($100000 region)
Green = PaletteRAM error ($400000 region)
Yellow = VideoRAM error
Pink = Bios selfcheck error ($C00000 region)
Cyan = Memory card error

The AES tests will only test the memory card if it is inserted and it is blank. It does NOT test the Z80 or other parts of the sound subsystem.

Raymond

Thanks for the info ! Extremely valuable information.
Sadly the AES has no ROMs onboard besides the BIOS and LO roms. No SFIX (text layer) and no SM1 (Z80 ROM for test mode).

I never knew the colors had any meaning. And I aways found pretty annoying to repair AES units due to not knowing this.

[Xian Xi]

I tested this, I have 3 neogeos and only one hasn't sound (with the same cartridges).

Check if there is continuity between the sound roms and the Z80.

[channelmaniac]

First things first. Check for sound output on the 16 pin Yamaha sound DAC chip with an oscilloscope. If you have a logic probe with sound output you can use that instead. If you have sound output there but no audio then check the analog (amplifier) section.

If absolutely no sound then check the trace continuity for the address and data line pins on the Z80 to the cartridge slot.

Pinouts for the Z80 can be found at http://www.datasheetarchive.com

If that checks good then get a magnifying glass and check for corrosion on the cartridge slot pins.

Next replace the Z80 CPU with a Z80A. SNK got cheap and used the slower clock speed related part instead of the proper Z80A.

Next replace the 6116 SRAM IC.

If that's not it, call an exorcist.

With that said, I can't remember ever having to replace the Z80 CPU on an AES. It's common enough on the MVS but the AES just doesn't have the playtime hours that an arcade version has to stress that CPU into failing. I've repaired bad traces.

Bad traces is a common problem on AES and MVS boards. Not only because they are subject to liquid spill damage (sodas, juices, rodent urine, etc...) but also because the poor process used to make them. It's my belief that the boards weren't properly cleaned at manufacturing time. I've repaired my unfair share of boards that looked pristine but had gunk down inside one small plated through hole that ate the copper inside to break the connection.

RJ