Graphics Problem

[GuinnessGuy74]

I have a graphics problem with my Ultimate MK3 board. I can see the video, but it seems as though every pixel is a different color! The pixels shift around a bit and and are eratic. While being on, the game will sometimes go back to normal for a little bit and then go haywire again.

I thought this was a power supply problem since I was using an ATX p/s with inadequate amps. I switch p/s's and I still have the same problem.

I was told it might be an address problem. Question is, where to start? I am not sure how to test the latches to see if they are all working correctly. Any thoughts/suggestions/comments anyone? I appreciate the help (as usual)!

Jim

[D_Zoot]

Can you post a picture of what the screen looks like when it's acting up??

Usually, if there is an addressing issue on the game board it will report in the boot-up self test.  If the board can't address the ram and rom's, you'll get an error message.    Manually testing the addressing lines requires a logic probe or an O-scope, and some basic understanding of how these circuits operate (I can't give you a simple explanation).

First off, get a multimeter out and verify that the voltages at the board are ok (+5 needs to be at least that, a tad higher, like 5.2 or so, is sometimes needed for some boards),  even a little low can cause wonky operation.

Since you say it comes and goes, that makes me wonder if you don't have a cold/bad solder joint somewhere or an iffy chip socket.  Inspect the board for poor or broken solder joints.   Carefully remove any socketed chips and reinstall them.    If the problem clears up after that, you have a bad socket somewhere. 

I doubt the roms are an issue, usually a bad rom is a bad rom and won't work sometimes.    Could be sketchy video ram however.   

Anything beyond what I've mentioned above gets into some pretty good board-level troubleshooting and you might be better off sending it out for repair.  These newer boards aren't simple to work on, I've got an MKIII on the shelf and I know what it's like.    I'm in the middle of a Revolution-X board myself  (%100 dead, no CPU activity at all) and all those surface mount devices are a pain!!


Regards,
D

[GuinnessGuy74]

D,

You hit the nail right on the head! Bad solder joint on a surface mount component! Took the component off and saw that the pad was practically gone. Fixed and goodbye graphics problem. Thanks a ton, I would have been trying to check every chip on the board before looking for that!

Jim