(Almost) dead Q950 - video artifacts w/ key lock @ ON

[pb3623]

I have a 950 that has been the most stable machine in my arsenal, just sitting there, serving up files from within A/UX. I also maxed out the RAM to 256 MB and threw a NuBus Ethernet card and SuperMac Thunder/24 card in (since I can't get my hands on the usual 950 "hen's teeth"). Well, I had an issue after swapping video cards (to troubleshoot an equally-frustrating issue with my 700 - see other thread in Peripherals) and, while I managed to get it back up, I have the weirdest side effect: when the key switch is left in the default (0-degree or up-and-down) position, I have wavy interference or artifacts on the display and it gets worse at higher resolutions.

But when I turn the switch to SECURE (which disables the keyboard and mouse), everything is normal!

I took the beast apart last night and unplugging the key lock from the logic board has no effect, but I didn't expect it to after other threads pointed out the position is "remembered" once set, even if disconnected.

In taking out the power supply, I took a quick look and didn't see any obvious electrical damage but that's way out of my wheelhouse. I know tantalum capacitors can burn out but I haven't an idea what to check next.

This appears to be the only side effect but I'm not 100% sure yet.

Thanks!  

 

[beachycove]

Very odd, but the key position is related to the ADB system....

 

[pb3623]

Very odd, but the key position is related to the ADB system....

Hmm, thanks for that. I forgot to mention it takes 3-4 rapid clicks for me to do anything but, to your point, I suspect something bigger than the keylock itself. I have a Snooper card and application I can pull out but I don't have loopback dongles so not sure what I'll be able to find out (and tracing VIAs, even spelling the word 'oscilloscope,' etc is not my bag)

 

[beachycove]

Sorry, I somehow overlooked that you had cross that bridge already.

Do you get this behaviour when the monitor is plugged into logic board video, or the Nubus card, or both? 

 

[pb3623]

I've always had less-than-reliable (but better than wonky) functionality with the Thunder24 NuBus, to the point where I put off any work involving new cards... and once I had to open to open the case and move something, I crossed fingers and left it alone. However, this situation called for Occam's Razor so I did pull it. With the card, it doesn't appear to boot or get me to the usual "Option" resolution select screen/cycle, without the card I get the OP behavior.

 

[beachycove]

My half-informed hunch is that you have a Nubus card that is either confusing the software or frying something in the hardware, possibly because it is itself fried. Fixing a fried Q950 is beyond my ken. However, the other possibility (system software confusion) would be a relatively easy thing to set right.

A/UX is supposed to rebuild the unix kernel when a nubus card is newly installed. I don't know for sure whether it does this for video cards or not, but let's assume that it does. I would therefore remove the card and run newconfig, ideally in conjunction with booting into single user mode or whatever it was in the 1990s, all of which details can be found in the troubleshooting sections of the old A/UX manuals.

I have in the past had really weird anomalies in A/UX involving a Supermac Spectrum 24 card, with text getting jumbled up on the screen (as in, the arse end of a line of text being run into the beginning of the line, so that the whole line is illegible, or just five or six letters being run together in the middle of a line on occasion, piled on top of each other). A/UX does not like certain fancypants video cards, essentially, and this has got to be software-related, as no such problems appear outside of A/UX with said card.

So my working hypothesis would be that popping in an exotic video card occasionally buggers up the software, which then needs to be put right. In your situation, I would test out the limits of that hypothesis, methinks, for a while before tearing the machine apart with a soldering iron.

 

[pb3623]

@beachycove: Thanks for the suggestions. I will strip out all the the cards, even the NuBus ethernet card and start with that. While I mentioned A/UX in the primary file server role this machine plays, I was getting (unrelated?) Sad Macs right after the boot process started on the MacPartition so I disabled that device ID via SCSI2SD and have been booting into my System 7.6.1 partition.

As stated above, I'm not sure of any other side effects, aside from the video interference and single clicks not registering.

 

[pb3623]

So a slight update...

Turns out I can resolve all of the video artifacts/interference by plugging the Thunder/24 back into its (or another) NuBus slot so this appears to involve the onboard video port/system. 

Something's still amiss, though. I get what's literally called "double panic" trap 27 errors when launching A/UX (3.1.1) so the kernel obviously finding something it doesn't like or not finding something it expects. But there are no disk errors on the MacPartition or A/UX slices and I've actually restored the SD card from a good image taken last month.

I ran Apple Personal Diagnostics, which detected a problem with the logic board! Run report for details! But the report only says, "problem with the logic board." How helpful.

Where do I go from here?

 

[pb3623]

So I found a possible CAUSE that might lay out next steps?

I have (or I should say had) an Apple Ethernet NuBus card (with the onboard 68000) and was happy with the improvement in performance. I just now remembered moving cards around in the 950 (because I wanted to test out a 601 PDS card that came with a 700 I recently bought), and I carelessly rushed pushing the Ethernet card into another slot. I remember this because it seemed lined up but didn't go in easily - if you have a 950 then you know the card slot cover is a bit tricky to line up and the vertical orientation requires you to eyeball the card going in).

When I turned the machine on, NOTHING - I immediately pulled the power cord out and removed both cards... and found that some of the pins were bent. IIRC, pins 1 & 2 of all three rows (A,B,C) which might have shorted the card? Because pin 1 should be -12V?

Anyway, can I assume this carelessness is the reason for my problems? Do I check the power supply first? Do I just chuck it and/or the logic board?