Quadra 950 Stuck on Grey Screen

[KGLlewellyn]

Hey all,

I recently got a pair of Quadra 950s, initially both ran just great, but one soon developed a fault. The machine chimes, completes the RAM test and loads up video, it looks like it gets to just the point before it initializes the toolbox, and then just hangs. The grey screen still has the sharp corners, it doesn't get to the point when the corners go rounded and the cursor shows up. I don't get any death chimes either. If I hit the NMI button, I do get the normal sad mac screen with the usual error code you get when hitting NMI before the OS starts loading.

It does this regardless of whether the hard drive is plugged in or not, and the drive is still set not to be terminated, per the requirements of this model. Plugging anything into the external SCSI bus makes no change.

It kinda -looks- like a SCSI issue, but I cannot be certain. Has anyone got any ideas on this one?

Thanks,

Kai

 

[jeremywork]

I have an ATTO SiliconExpress IV which went from working, to intermittent, to failed in a short span. While intermittent it produced the same symptoms in my 950, only advancing to the screen with rounded corners when the SEIV was in a working state, otherwise just hanging at the square corners. Based on this I could guess something in the SCSI controller initialization process is breaking.

 

[KGLlewellyn]

Hmm, yeah. The more I think about it the more I feel it would be a SCSI issue. I'll see if I can take a look at the SCSI related IC's under the microscope and see if there's any cracked solder joints.

Might give diagnostic mode a try too.

Okay, U43 and U48 are 53C96 SCSI Controllers - One for each bus https://datasheetspdf.com/pdf/770776/AMD/53C96/1 - I'm gonna focus my attention there.

 

[beachycove]

You have the required terminator on the end of the internal scsi ribbon cable, right?

 

[KGLlewellyn]

Yes, it's attached. I could swap it with a known good one from my other 950, just in case it might've failed.

I guess I could probably test this myself, but by your suggestion the 950 won't get to the flashing ? floppy icon if nothing's connected in either SCSI connector?

 

[KGLlewellyn]

I've made progress with Diagnostic mode, it indeed reports an issue with the SCSI Bus. So my guess is probably a bad solder joint or failed SCSI Controller IC (NCR 53C96) - Incidentally, if anyone has a battery bombed board with a NCR 53C96, please hit me up!

Diag mode test results
Test: *N009A00010000 (53C96 SCSI Test)
Result: 020001000B0B

B results a SCSI failure. I think that maybe because I'm getting two B's, it is reporting an issue with both controllers. Just a hunch though.

Also this should be documented somewhere better than Internet Archive: https://web.archive.org/web/20140921015903/https://mac68k.info/wiki/display/mac68k/Diagnostic+Mode