PCB has odd graphic glitch

fuko · Post by **fuko** » Fri May 02, 2008 5:59 am

Got a board in the mail the other day, and while playing it tonight I noticed there were a couple of graphic glitches in some of the backgrounds. Very subtle, but on certain levels there appear to be the odd wrong or extra sprites, graphic anomalies, scrolling by in the background. Everything else on the board works great.

I'm wondering if anyone can suggest something to try to correct this? I've read in the past that it can be caused by dirty jamma connectors, or poorly seated ROMs. But could it be more something more permanent, like ESD damage, or simply old age (15 year old board)? Just curious to hear if anyone has had experience with this kind of thing.

Ex-Cyber · Post by **Ex-Cyber** » Fri May 02, 2008 12:47 pm

Something like that sounds like a ROM or VRAM problem. If the board has a proper self-test that passes, it could be caused by bad capacitors.

FWIW, my knowledge of arcade hardware is pretty much purely theoretical; it's not a hobby I can afford to pursue right now.

Stefan_L · Post by **Stefan_L** » Sun May 04, 2008 9:54 am

What game are you talking about?

fuko · Post by **fuko** » Sun May 04, 2008 6:22 pm

It's a Nostradamus board that otherwise looks to be in good shape. One or two of the small ceramic disk capacitors look slightly bangled/chipped. Nothing bad mind you, but a hint of metal is showing on top edge of one of them.

I cleaned the edge connectors so that's not it. The board is very clean. I also checked for badly seated ROMs, but they are all soldered in place and look to be fine.

Basically I am trying to rule everything out before I suspect it to be bad logic on the board. I want to look into my +5v next to make sure it's correct, although never had a prob with other games, and I have 5 or 6 others from this time period. Not sure how to adjust this on an Egret II. I think it's the single blue pot at the bottom of the power supply unit?

Post by **Dave_K.** » Sun May 04, 2008 6:28 pm

Can you take a pic of your Nostradamus board? Are any of the rom chips socketed? I'm having color problems on sprites with my Nostradamus as well and think I'll need to reburn the roms.

fuko · Post by **fuko** » Mon May 05, 2008 5:41 am

All the ROMs appear to be soldered directly to the board

Stefan_L · Post by **Stefan_L** » Wed May 07, 2008 4:08 am

So did you check the testmode?

Post by **Dave_K.** » Wed May 07, 2008 5:25 am

fuko wrote:All the ROMs appear to be soldered directly to the board[/img]

Yep same as mine. Going to be expensive to get this re-burned.

I agree with Stefan_L, run through the sprite tests (compare with Mame to see what things should look like).

fuko · Post by **fuko** » Thu May 08, 2008 4:00 am

So this turned out to be an interesting exercise. I'm posting the results because I think the process is a good one for ruling out issues that could be environmental vs. ones with the board logic/assets

A lot of boring pattern comparison, but then I start to see some slight differences. They're subtle, but they are there.

Example 1

MAME:

My board:

Example 2:

MAME:

My Board:

Basically patterns where there shouldn't be and vice versa. In some areas it seemed like the addresses for whole sections got shifted (is that even possible?) I also thought I noticed some color pallet shift in some sections as well, but I can't be 100% sure...

How much of this is due the ROM dump I was comparing with being from another region or something altogether different, I cannot say. Anyway, not sure what to make of it at this point.