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MV1FZNB2 Garbage Screen/Green Screen Loop

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Martyken

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Hi all, took out my MV1FZ board out of storage to enjoy some KOF however I think I might have caused an accident.
Played it for a few hours. however volume on the board was loud and kept distorting, so I went to tinker with the audio pot (VR1) - turning it did not make any difference to the game audio.
Now that I've touched the pot, trying to get a game to boot again results in the green screen looping, and without a cart results in the watchdog/click of death.

Where should I be looking to diagnose the mess I potentially have created for myself? :(

Thanks!
 
I don't think you've created a mess for yourself, just changing the volume wouldn't have caused the board to stop booting. With that said, it's a rather strange situation.

Start by checking the voltages at the board edge and, if your board's BIOS is socketed remove it and insert it again.

If the problems are related it may be that the amplifier or bad capacitors in the sound circuit are causing unwanted noise or voltage ripple. This could lead to instability and the board resetting. I can't think of any other causes that would explain both problems occurring more or less at the same time.
 
Thanks for the tips, tried reseating the bios but same problem persists :(. Looks like it could be the audio amp or the capacitors themselves.
 
Turn all dip switch on, then power on. You'll go into "Work ram test". Let it run for few seconds and then power off and switch dip back to off.
See if it works. If it's repaired, ti was just backup ram corruption.

Your issue may also be a real calendar error, but the buggy bios is not able to show it and reboot. Then you need to fix what's wrong with it.
 
Rom1 said:
Turn all dip switch on, then power on. You'll go into "Work ram test". Let it run for few seconds and then power off and switch dip back to off.
See if it works. If it's repaired, ti was just backup ram corruption.

Your issue may also be a real calendar error, but the buggy bios is not able to show it and reboot. Then you need to fix what's wrong with it.
Click to expand...
I've tried leaving it on the work ram test screen for a few minutes, but upon reboot nothings changes. Going to see if even a unibios would let me bypass the watchdog to see if the issue is actually audio related or relating to the real time clock
 
Click of death is most likely a RAM failure - Work RAM or Backup RAM... or a failure on the control lines to the Backup RAM. See if you have signals on /CE and /CS. It's normal for one to be tied to ground... but the other should not be stuck low. If both are low then you'll have those RAMs spuriously outputting data to the bus and crashing the CPU.

Those control lines for the Backup RAM (and the power for them) go through the area powered by the battery. On boards with NiCd batteries it's common to have that area roached by battery damage... but yours should have the rechargeable lithium and those rarely leak.
 
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