MV1 issues (Sound/Z80 Error/Test Mode)

unofficialitguy

Hardened Shock Trooper
Joined
Feb 16, 2014
Posts
425
I recently received an MV1 board that is behaving erratically and wanted to see if I can get some guidance on possible repair or if I should just list it for cheep on a sales thread.

When I got the board, it was booting into a controller test 9 times out of 10 and was listing a number of the joystick controls as 'on'.

When the board didn't boot to the test screen, the system loads the game and the controls work fine.

The only thing not working properly is the audio. It is super distorted once that the game is loaded. The Neo Geo startup music is fine and the sound test is fine but as soon as any game is loaded, bad audio.

This behavior is only happening with this board tested on two cabinets with the same results.

I pulled the UniBIOS 2.x that was installed on the board when I got it and popped in a U.S. BIOS that I had on hand and it stopped doing the control test boot issue. Tested the UniBIOS on another board I have and it works fine.

I went ahead and did an audio cap kit on the board and booted it up. The first few times it loaded to a Z80 Error screen. I booted it into test mode and it was failing the controller test again. I applied some pressure to the BIOS chip and it stopped getting false 'on' signals from the controls.

I restarted the machine again and it boots to the game now but with distorted audio.

I'm thinking of reflowing the pins for the BIOS socket but I'm looking for other suggestions first so I can stop chasing my tail on this one.
 

unofficialitguy

Hardened Shock Trooper
Joined
Feb 16, 2014
Posts
425
So I reflowed the contacts on the BIOS socket and reseated the cart connector board. Issue persists. Halp!
 

Xian Xi

JammaNationX,
15 Year Member
Joined
Dec 1, 2005
Posts
27,748
The bios doesn't affect the controller inputs, it only reads it. It's more due to the flexing of the PCB when you push it down. Most likely lifted pins on the PRO-CO or something unless the CO or a bunch of pullup resistors is bad.
 

channelmaniac

Mr Neo Fix-it
15 Year Member
Joined
Nov 29, 2005
Posts
4,275
Clean the slots to get rid of the scratchy audio and intermittent Z80 errors...

Also check for a roached battery that has leaked on the board. It will eat traces like candy and cause problems.
 
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