Raiden 2 pcb, graphic problem (SQUARES !)

[nork69]

hi everyone,
Well to be honest with you, I don't really know where to throw myself with this problem.

Like you all know, a picture = 1000 words so here:



I'm not an expert, I start the game and after around 15 sec, ship, bullet and moving object become colored squares.
I touch the 5 capacitors, one of the biggest one 1000uf/16v, became REALLY hot. I ask a brother to change it, NOW, same problem but 45 sec later (but capacitor is not hot, just ok)

Have you ever seen something like that ?
Ideas how to fix it ?
My eyes are ready to read you

Thanks

 

[Kid Panda]

I would venture to say it's a Video Ram chip issue. Are any of the smallish chips on the board getting extra hot? Possibly one near the capacitor that has been replaced? If you have one that is getting blistering hot, that would need to be replaced.

 

[hezkezl]

What is the voltage at your power supply?

Also, I like using the freeze spray trick for scenarios like this. It's most likely a heat related issue, so I take a can of compressed air, invert it, and spray it on the board in various locations. Often times, when you spray a component, the issue will fix itself until the frost melts. Replace that component, and you are usually good to go.

 

[bustedstr8]

It sounds like it could be loss of connectivity between the OBJ Rams / Roms and the SEI252 graphics chip. The SEI252 is a fine pitch QFP and thermal cycling can often cause cracked joints on it. Try slowly pressing down on the SEI252 after the errors begin. If you get a response from the squares (changing colors, flickering or if your lucky full sprites) then the chip will need to be reflowed.

 

[awbacon]

I know it's not "right", but that screenshot looks pretty awesome

 

[nork69]

Well,
after some try, (to feel if some chip become hot), now I'm facing a new problem.
Game start but freeze instantly. No sound nothing and freeze at the first screen.

 

[hezkezl]

Do you have a multimeter? You really need to check your voltages. It's hard to diagnose something like this just by the symptoms.

You could have a miscalibrated or bad power supply. It's pointless trying to debug a board if your power is bad, so that is always the first thing to check.

The next thing I do in a situation like this is use a logic probe to check the clock signals on the CPU to make sure everything is clocking correctly, and try to trace the problem down.. But this is not a quick and easy process.

It looks like you may have some issues with your address decoder circuitry. That could potentially cause issues with both your sprite data and your program code, causing garbled sprites, and freezes and such.

 

[Xian Xi]

It sounds like it could be loss of connectivity between the OBJ Rams / Roms and the SEI252 graphics chip. The SEI252 is a fine pitch QFP and thermal cycling can often cause cracked joints on it. Try slowly pressing down on the SEI252 after the errors begin. If you get a response from the squares (changing colors, flickering or if your lucky full sprites) then the chip will need to be reflowed.

From my experience with Raiden II boards, this is usually what it is.