advice on fixing a faulty kof94 aes cart

[wesprice]

hey all long time no post... i have a bit of free time so dug a few dead carts out of the box of shame, im currently working on a kof 94 aes that looked like it had been under the ocean for a hundred years, never seen the ground pins on the c roms rot off before...

anyway.. the graphical issues have been fixed and the cart runs the game now but there are some sound issues... most of the tracks seem ok but there is clear distortion in sound effects coming from somewhere.. maybe the vroms? is there any bios that can verify the vroms on the cart without em having to remove them?

im expecting it to be some data line / addressing chip causing the issue but it doesnt hurt to verify that the roms are ok.. the m1 was fine.

if anyone knows a way i can calculate which chip the audio should be in thats causing issues (i can play them on the unibios jukebox) that would also help me isolate if the problem is a specific chip without having to remove it.

 

[Neo Alec]

I have a similar thread currently, so I feel your pain.

There is no way to check the V rom chips without desoldering. The bios can't access them.

Here's a trick to try and narrow down which V roms that will hopefully work better for you than it did for me. Download the roms from the net and then decode the V roms using ADPCM-B decrypter (it will kind of decrypt ADPCM-A too, at least enough to identify):

View topic - VGM Logging with other Emulators - Forums - SMS Power!

www.smspower.org

Listen to what's on the roms and use that to determine which roms aren't working.

Also, the PCM chip on the board could be bad. Furrtek makes replacements.

 

[wesprice]

Hey thanks a lot, that is really helpful.

It's been at least a decade since i've messed with any neogeo stuff and i was hoping there were more tools / bioses etc to help speed up diagnostics

Ill pull the roms and check their contents against the known good dumps, if its a bad chip then the repair should be pretty straight forward but if they all verify then having the abilty to see what is in each chip with that decrypter you linked will help me trace the signal paths from that chip to the neogeo.

Will post an update when there is any development, thanks again

 

[wesprice]

Holy crap some dirt under those chips... I think it had been kept outside or something! Anyway would like to say thank you for the recommendation, after converting the V roms from mame to audio files I found that all the corrupted samples were in the V2 ROM.

After removing some of the chips and noticing the amount of dirt under them I decided to remove all the chips from the PROG board and clean the board and chips up before reassembling.

I could also dump and verify all the roms.. as expected the V2 rom is bad, must be an internal problem with it as the first 1/3rd of the chip is fine but after that the data is intermittently messed up.

Replaced it with an EPROM and the game works fine now with all corrupted sounds playing as they should.

 

[Neo Alec]

Wow, perfect. All fixed up perfectly already!

I'll be lucky if I get around to dragging out my tools and desoldering my Irritating Maze cart one of these weekends.