Tech: Konami Sunset Riders pcb graphics issue

debaser138

Well-known member
Joined
Mar 1, 2009
Messages
1,029
Reaction score
64
Location
Grand Rapids, Michigan
I've got a Konami Sunset Riders pcb that works but is having some major graphics/color issues. The board plays and I can get into test mode and it passes all the tests for the masked roms along with the

I pulled the (2) AM27C020 roms from locations 8G and 8E. The one at 8E was bad so I erased it and reprogrammed it. The rom verifies fine now but it didn't fix the problem.

There are two more roms at 10G and 10E but they are not labeled to say what they are (such as AM27C020) so I'm not sure how I should read those with my GQ-4x4 burner. Can someone tell me what kind of roms they are?

Here is a video I took of what the board is doing:

https://www.youtube.com/watch?v=se_HQTCam20

Any help would be appreciated. Thanks!
 
They are most likely readable as 27c010 but I doubt that is the problem. Surely something wrong in the palette/mixing hardware.

You were correct that they were 27C010's. I pulled off the sticker and they were labeled underneath with that. I dumped each one and the rom at 10G is bad. I also dumped the contents of the 27C512 at 2F and that was fine. Looks like I need to order some 27C010 eproms.

It sounds like you don't think that will fix the problem tho.
 
I found a 27C010 in my stash of eproms. Burned it but no change. Looks like the issue is definitely elsewhere.

I've not done much at all with arcade game board repair. Seems like this one wouldn't be too difficult as the game is running and the issue appears to be in the video output section of the board.

Anyone adventurous feel like trying to help me thru fixing this board? I've got most of the tools except I don't have an oscilloscope.

Thanks!
 
I'd probably focus my efforts on the 053251 priority mixer and the palette SRAM (18J/18H).

I was checking out the MB8464's at 18J/H per your suggestion and I found that on 18H the CS1 pin (pin 20) is a dead short to the ground pin (pin 14). That is not the case with 18J.

I tried looking in the manual but I can't see a breakdown of 18H and 18J, unless I'm completely missing it.
 
A /CS1 tied to ground in this case probably isn't something to worry about.

Sounds like you have found the schematics already, so basically check every TTL on the palette page (the one with the RGB outputs).

The RAM being bad is unlikely - because the sprite colors are correct - usually (but not always) when a RAM fails everything will go - it would be really unusual for the RAM to be good for sprite colors but not tilemap colors.

Therefore it seems most likely the mixing/addressing TTL leading up the palette RAM is the problem.
 
Back
Top Bottom