Trying to fix Captain America and the Avengers

[Catzoo]

Hello,


I'm still new to fixing PCB, so i'm looking for some clues on this one.

I'm trying to fix a Captain America (Data East) that shows nothing on boot, black screen, no sound. From what i know, it was working fine before storage.

It seem to had a rough life, most of the big rom (C31, C34, C38, C50 and C57) had a lot of rust on it that i tried to clean, and tracks on the component parts of the PCB had black dots everywhere, so i guess it's not a good sign. It's impossible to track them all, but from what i've checked with continuity, it's all good. Solder side is perfect.

From what i've read so far, this could be a lot of things obviously, but first things to check should be : power, CPU and reset circuit.

However, with this hardware, CPU is not obvious and i can't find any schematics.

Are there any checks i could do with a multimeter and a logic probe ? (like is the crystal ok, does the CPU do something etc.), can i short and damage thoses custom chips trying to probe them ?

Any help would be appreciated

 

[Catzoo]

Ok so i've just spent the last two days working on this, and finally i managed to do something with it !

First, i've decided that this rust on the rom where way too advanced, so i've decided to take a shot and used a whole fiber glass pen to remove whatever i could. It's still not perfect, but it's definitely an improvement. Cleaned it again and let it dry for the night.

Before :


After :


Still nothing this morning

But after another good visual inspection, i found no less than 3 shorts on the solder side ! The pins on this side are so long that most of them were smashed down, and 3 of them were touching another pin ! Lifted the culprits and VOILA, the game booted !

Great news, but i'm still not done with this one.

First, i've noticed two things : some text were missing, and the sprites seem to have some "parasite" around them, like flickering white dots.



Powered down the board, and decided to remove every eprom, clean the pins with a carbon brush, and reseat them.

It gave me this, still not good and not really an improvement (look how portraits where good before, then just a plain color)



Ingame, sprites and some background still have theses white flickering dot, but more importantly, some elements are messed up.



I really want to dig theses and check what's inside theses eprom, but i don't own any Eprom reader/burner, so i'm basicaly stuck now.

Here's a video of the game running (notice how the demo has some part of the screen broken but not ingame. It starts to get crazy near the car in flame where weird white lines appears on the whole screen)

Any help or advice would be appreciated

 

[xodaraP]

At this stage I think you need to remove and verify the mask ROMs, and replace as necessary, you also need to confirm the continuity (traces will be on both sides of the board for the ROMs)

Great to see you've got as far as you have just with cleaning up and straightening the pins, nice work!

 

[Catzoo]

Thanks ! That's what i was afraid of, as i don't have a desoldering gun nor a programmer right now, and it's pretty expensive stuff :/

Anyway, as it seem to be very specific bug (HUD, text background, Data East logo), is there any way that i could try messing with the code in mame in different roms to know "which" one might be the culprit ?

I've seen that stuff like that is possible but i have very little knowledge in code, but i "suppose" that you might make a "snap" (for exemple, at the data east logo ?) and see where the "data" is coming from ? Or am i saying nonsense ?

If anybody can recommend tools for me and try messing with that, i'd love to know where to start. Anyway, i'm gonna have to check eprom first, then mask.