SE/30 garbled graphics

[splashdust]

Hi, I have recently transferred all components from a badly battery bombed SE/30 board to the new Reloaded PCB by Bolle.


I’ve gotten to the point where I get a picture, but the graphics are garbled. I have checked all solder joints and can’t find any bad connections (though I may still have missed something).


Otherwise everything essential appears to work:
* chimes on boot.
* displays floppy with blinking question mark, although garbled.
* mouse cursor can be moved, but is also garbled. It also sort of leaves trails behind.


Pressing the interrupt switch causes a sad Mac with an error code, but it’s impossible to read due to the garbled graphics.


What could be the cause of this particular style of problem? Bad video buffer ram or multiplexers? (All the F258s are new, but I reused the F253s)

Any suggestions on where (and how) to start trouble shooting?

 

[cheesestraws]

Pressing the interrupt switch causes a sad Mac with an error code, but it’s impossible to read due to the garbled graphics.

This is expected if you do it before the System boots, it's not a symptom of this problem

 

[splashdust]

This is expected if you do it before the System boots, it's not a symptom of this problem

Ah, thanks for clarifying that. Suspected that might be the case, but wasn’t sure!

 

[KGLlewellyn]

IIRC the SE/30 utilizes the onboard RAM SIMMs to draw the video buffer, problematic RAM has been known to cause graphical issues. I'll admit I haven't seen it quite this bad, but as far as troubleshooting goes, I'd start with that.

I would also try and grab a schematic of the board and trace back through anything related to RAM and the video output.

It's possible one of the IC's on your board might be faulty too, not sure which one it could be. Some other more experienced folks might have a better idea.

 

[splashdust]

IIRC the SE/30 utilizes the onboard RAM SIMMs to draw the video buffer, problematic RAM has been known to cause graphical issues. I'll admit I haven't seen it quite this bad, but as far as troubleshooting goes, I'd start with that.

I would also try and grab a schematic of the board and trace back through anything related to RAM and the video output.

It's possible one of the IC's on your board might be faulty too, not sure which one it could be. Some other more experienced folks might have a better idea.

Thanks! I’ve tried other (known good) RAM modules, so they should be fine, but I guess there could still be a bad solder joint somewhere in the RAM circuitry.

But I believe the SE/30 uses dedicated VRAM (the two 41264 chips), so I’m thinking one of those might be bad. I found some NOS ones on eBay that I’ve ordered. Perhaps it’ll be as simple as replacing those!

Not a bad idea tracing out the schematics though, I’ll do that too. A good learning experience if nothing else!

 

[Bolle]

I approve that Dimmu Borgir album

This looks like VRAM addressing issues. I’d use new F253s. At least one of them is usually bathed in cap goo and tends to die.

 

[splashdust]

I approve that Dimmu Borgir album

This looks like VRAM addressing issues. I’d use new F253s. At least one of them is usually bathed in cap goo and tends to die.

Spiritual Black Dimensions, truly a masterpiece!

Thank you, I’ll try getting new F253s!

 

[splashdust]

@Bolle your intuition about the F253s was spot on!



Never have been so happy to see that blinking question mark!

Thanks a bunch!