[3DGraphics]

I recently acquired an Indigo 2 with IRIX 6.2 installed. The system worked fine with the previous owner.

I was able to have the Prom load but after that the screen would go black as IRIX started booting. I believed the problem was that the monitor was not sync-on-green. After trying mutiple monitors with unknown SOG status with the same result I finally got a confirmed sync-on-green compatible model yet the problem remained.

A few days ago I ran the Diagnostics in the prom. It ran for a few minutes and appeared to freeze, I walked away and shortly after noticed the machine restarted itself so I don't know what info showed on the screen. I ran the Diagnostics again, this time it froze for a long time and did not restart. During this time the LED alternated between steady green and flashing green. I manually restarted with the switch and the machine booted into IRIX. 

I played around and tested some stuff. I ran Alias 8.5 which seemed to work fine. I left the room for 35 minutes to eat dinner and when I came back the monitor was black with the indicator light blinking meaning no signal. I tried the mouse, keys, but nothing worked. The LED light was green. I'm pretty sure it wouldnt turn off by the power switch I had to restart it with the switch and then power off in Prom.

Today I tried again, it loaded right into IRIX. I was able to login into root via Unix Shell to change the date. I just explored the DesktopHelp and after about an hour tried to run the text editor Jot, I clicked the icon and immediately the screen went black indicating no signal detected. Again couldnt revive the system via mouse or keyboard.

After restarting the system it did not successfully boot IRIX and went from Prom to black again as before I did the Prom Diagnostics. I expect if I run the Diagnostics again I can get it to play nice, but only for so long.

I don't know if the system crashing when a certain program is loaded is indicative of a hard disk problem or what. There was certainly some jostling during transit as the hard disk ribbon cable had come completely disconnected from the connector near the processor. I tried making sure everything else was secure but I have no experience with such things and didnt see anything that looked wrong.

I have never used Silicon Graphics computers before so any advice would be greatly appreciated. Thank you.

[Raion]

If you can setup networking, you should try and see if telnet is still running during a screen blackout (you have to be in IRIX for this to work).

However, IRIX 6.2 is essentially even more obsolete than later IRIX releases, so it's an exercise in futility - if you don't have anything that you need on that install, I'd install 6.5.22 and go from there.

[dexter1]

These intermittent problems suggest that it is not OS dependent, since it occurs at the PROM IDE diagnostics as well as booting into IRIX.

I'd suspect loose components, faulty memory or a PSU problem. The fact that you cannot turn off the system via the power switch sounds like it may be the latter.

But make sure everything is secure and seated properly, you might need to carefully reseat every component.

Diagnosing it might be problematic since we don't exactly know what's inside. I would suggest minimizing components:
Start with one set of 4 simms and let it run PROM diagnostics. If it is still crashing or rebooting, let it sit in the PROM for a couple of hours and see if the problem manifests itself when the PSU is heating up.