Sunset Riders - Visual Artifacts

[tika]

I've recently purchased a Sunset Riders PCB that has visual artifacts when the game is running. The ROM check fails on IC 16K which leads me to believe the IC is dead considering these fail all the time (from what I've read). The game fully plays and the sound works fine, so it's just the graphical output that has issues.

I've checked the board around 16K and there doesn't seem to be any broken traces as it looks like the 16K IC has been replaced/reflowed previously, perhaps to fix this issue.

I'm looking to firstly replace the 16K IC, but I haven't been able to find a replacement part online - is there an equivalent off-the-shelf part that I can use instead? Is there anywhere else that I should be looking at before replacing the 16K IC (SRAM?)?

 

[djsheep]

From memory I think the chips on that board are 27C4096 / 27C4002. Check the MAME driver.

 

[tovar]

They are mask rom, equivalent AM27c400.

 

[tika]

They are mask rom, equivalent AM27c400.

Thanks for the info on the IC type - that helps me a lot.

I checked the MAME driver as per @djsheeps recommendation (https://github.com/mamedev/mame/blo...7e581aea37895/src/mame/konami/tmnt2.cpp#L3471) and see that the 16k IC data is the same across all ssriders ROM sets, but couldn't see what sort of IC would be a suitable replacement for the original IC.

Is there a mapping by any chance that that lists the types of replacement IC's that can be used to replace original mask roms? I'm new to burning ICs, and finding replacements IC models for original ICs has been a bit painful

 

[Asure]

Not to get your hopes down, but i've seen similar issues where the custom that is connected to this chip is failing from old age.
If i recall from my repair attempt, i had a similar problem where one of the custom pins was dead inside the custom, causing a line through the graphics.
In your case it seems to be floating, mine was high or low.

I cut the offending pin loose and scoped it, the mask rom was outputting valid data, so the problem had to be in the custom. Even jumpering it straight to the custom did not improve, the line remained. (The board is on a pile somewhere now.)

I hope in your case the custom is OK and it's bad output from the mask rom.

 

[tovar]

If you suspect a particular Mask ROM is bad:

The mask ROMs in Sunset Riders:
40 pins, Mask Rom equivalent to Eprom AM27C400.

42 pins,Mask Rom equivalent to Eprom M27C800.

 

[tika]

Not to get your hopes down, but i've seen similar issues where the custom that is connected to this chip is failing from old age.
If i recall from my repair attempt, i had a similar problem where one of the custom pins was dead inside the custom, causing a line through the graphics.
In your case it seems to be floating, mine was high or low.

I cut the offending pin loose and scoped it, the mask rom was outputting valid data, so the problem had to be in the custom. Even jumpering it straight to the custom did not improve, the line remained. (The board is on a pile somewhere now.)

I hope in your case the custom is OK and it's bad output from the mask rom.

Thanks for the info - hopefully it's not the custom otherwise it'll go into my spares pile but hoping it's just the mark rom (fingers crossed).

 

[tika]

If you suspect a particular Mask ROM is bad:

The mask ROMs in Sunset Riders:
40 pins, Mask Rom equivalent to Eprom AM27C400.

42 pins,Mask Rom equivalent to Eprom M27C800.

That's great info, thank you very much. I'll get some AM27C400/MX27C4000 and M27C800 to see if it'll sort out the issue

 

[bodgit]

If you suspect the mask ROM is bad, you can always try reading it with your programmer and then compare it to what's in MAME.

 

[djsheep]

Thanks for the info on the IC type - that helps me a lot.

I checked the MAME driver as per @djsheeps recommendation (https://github.com/mamedev/mame/blo...7e581aea37895/src/mame/konami/tmnt2.cpp#L3471) and see that the 16k IC data is the same across all ssriders ROM sets, but couldn't see what sort of IC would be a suitable replacement for the original IC.

Is there a mapping by any chance that that lists the types of replacement IC's that can be used to replace original mask roms? I'm new to burning ICs, and finding replacements IC models for original ICs has been a bit painful

@twistedsymphony has a great reference here:
Post in thread 'EPROM Guide for BIOS and simple ROM-Swap Conversions'
https://www.arcade-projects.com/thr...simple-rom-swap-conversions.13620/post-221031