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CPS3 with garbage screen

kazuo

kazuo

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Tale as old as time...

Helping a friend debug a CPS3 board; at power on, we're getting a garbage screen very similar to this one. Seems to happen with Super/Ultra BIOS carts, as well as cartridges with original BIOS/batteries. I tried dousing the cart slot with deoxit, didn't make any difference.
  • Reading 5.05V at the JAMMA edge.
  • Checked all of the customs for obviously bent or loose pins, not seeing anything obvious. I do not have a scope, but I used a magnifying glass under a bright light.
  • No obvious signs of corrosion.
  • The cart slot is very bent, but none of the pins look damaged, and I don't see any bad joints.
So before I go desoldering cart connectors or reflowing every custom on this board, I'm wondering if anyone has any advice surrounding anything obvious I might be missing as far as troubleshooting might go.

Thanks!
 
I spent four hours last night getting an untested motherboard to finally boot. I had garbage screen half the time, so I took a fiberglass pen to the cart edge itself and that seemed to help.

I still feel like improper SIMM configuration can cause this, but perhaps someone can confirm. At least you are getting video, so that is a good sign.
 
I'm skeptical that it's an issue with the cartridges, since they both work perfectly fine on another board with a 3S Darksoft install on the SIMMs; the DS cart just boots, and the other cart complains about needing to rewrite the SIMMs. Expected behavior.

My feeling based on past experience is that the carts should still boot, and either ask for more memory (the board I'm working on is one SIMM short, I haven't bothered yet) or a rewrite (the original cart we're using probably doesn't match whatever is on these SIMMs). It's possible I'm wrong though.
 
The DS cart requires the 3rd strike population of SIMMs (slot 6) regardless of what game you write, else you get the not enough memory error. I missed this at first, but sounds like you are not even seeing that anywhere?

If you swapped all the SIMMs from a verified working unit to your friends motherboard, I am curious what the result would be.
 
That's correct, the behavior of the DS cart when it doesn't have enough memory is it throws an error telling you you need more memory. I don't get that. All I get is a garbage screen, regardless of which cart I use, how many SIMMs I have (including no SIMMs at all), or whether or not I have a cart in the slot. Exact same garbage screen, virtually identical to the one in the other thread I linked in the OP.

After giving the customs a quick scrub with a toothbrush just to check if I missed anything obvious under some grime or whatever, I came across some loose pins on a couple of corners of the PPU. Reflowed, no change, same garbage screen.

I may just reflow all the customs and if I get the same screen, probably going to give up unless anyone has a better idea.
 
Still getting the exact same garbage screen. Writing this one off as a parts board.
 
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