Simpsons Graphics Glitch

s0ma

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I have some glitchy lines being drawn regardless of what screen I am on. All of the self-tests pass without note.

Screenshots:

http://db.tt/07fodyDj
http://db.tt/QeaICwiP

I believe i've pushed down all of the eeproms as far as they will go. Should I attempt to re-seat them or is there something else that is commonly the cause of this?

I should probably mention that this is my 2nd PCB so far :D
 
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Man you're probably not going to be able to easily fix it, I had one like that too. Replaced several of the ram chips and it still was doing it.

You might try to adjust your 5volt a little bit up or down, if it's in the wrong area it might cause glitches like that.

If not, you've got a issue somewhere with an IC, it's probably not an eprom thing (especially since they're passing the self tests) but it wouldn't hurt to clean and reseat them.
 
LyonsArcade - I adjusted the +5 up to about 5.4 or 5.5 and the lines went away. I didn't have a lot of time to test it this morning before going to work but I plan on checking it out again later tonight. Thanks for the pointer. :)
 
LyonsArcade - I adjusted the +5 up to about 5.4 or 5.5
wtf_5487211_480x300.jpg
 
With a handful of exceptions, you should never crank the +5VDC to 5.5 and above on a board.

You're putting a ton of stress on the components and will probably (if you haven't yet) fry many of them. Especially considering Simpsons is a relatively small single board setup.

If a board like this is showing issues don't go past 5.1 or maybe, 5.2VDC max in the "ruling out the power supply" phase of your debugging.

(looks over at stack of dead Konami boards) they're gentle creatures, they are.
 
With a handful of exceptions, you should never crank the +5VDC to 5.5 and above on a board.

You're putting a ton of stress on the components and will probably (if you haven't yet) fry many of them. Especially considering Simpsons is a relatively small single board setup.

If a board like this is showing issues don't go past 5.1 or maybe, 5.2VDC max in the "ruling out the power supply" phase of your debugging.

(looks over at stack of dead Konami boards) they're gentle creatures, they are.
Oh, awesome. Thanks for the info. Did not know that! :)
 
You need to measure it at the board, where it should be nominally around 5VDC. Be sure to clean your edge connectors and sockets as that may introduce a voltage drop if it is not making a clean connection.
 
You need to measure it at the board, where it should be nominally around 5VDC. Be sure to clean your edge connectors and sockets as that may introduce a voltage drop if it is not making a clean connection.

I was finally able to measure the voltage at The PSU (AC/DC), the jamma connector, the board and every removable eeprom.

The PSU's 5v DC was between 5.0 and 5.1. The AC was between 120 and 121. The Jamma Connector and the board were at 4.8 - 5.0. All of the eeprom sockets were at 5.0 when measured.

I removed all of the eeproms that were in sockets and cleaned them and carefully replaced them. I also cleaned the edge connector as well.

The graphics issues persist. They haven't gotten any better or worse. I did notice that the artifacts on the screen do not seem to appear during the boot rom test. They appear once the game actually "starts". If i go into the options and run the rom test there the artifacts are present.

I was curious if anybody had any additional information on where I could look next? I really appreciate all of the pointers so far.
 
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Its not an eprom or mask rom problem, GENTLY push on the 4 big square chips in turn when the game is running, watch to see if there is an improvement.
 
Its not an eprom or mask rom problem, GENTLY push on the 4 big square chips in turn when the game is running, watch to see if there is an improvement.

I pushed down on each of the 4 big square chips per your recommendation Womble and there was no change.

On a side note I turned the voltage temporarily up to 5.2 for a few seconds and the sawtooth pattern on the edge of the picture disappeared.
 
I'm wondering if you've had any luck isolating this problem. I've got a friend with one of these games in their business and it looks exactly the same as your pictures. Is the voltage making it to the board too low? Is this a failing RAM chip(s)?
 
I'm wondering if you've had any luck isolating this problem. I've got a friend with one of these games in their business and it looks exactly the same as your pictures. Is the voltage making it to the board too low? Is this a failing RAM chip(s)?

No such luck as of yet. Still working at it as I find time. Recently had some questionable looking caps replaced to no avail. I think I might go after the RAM next.
 
a pic of the grafix problem is in order. I have seen where a bad clock going right into a ram chip will cause video issues.
 
I'm wondering if you've had any luck isolating this problem. I've got a friend with one of these games in their business and it looks exactly the same as your pictures. Is the voltage making it to the board too low? Is this a failing RAM chip(s)?

Winslow, if you or your friend solves the gfx glitching please let me know :) I'll do the same if I figure it out on my end.
 
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