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Monitor on PowerMac 8600

dcr

Well-known member
The photo below is what the monitor screen looks like on my PowerMac 8600.

Can anyone tell if that loos like an issue with the monitor itself or would it be with the PowerMac's video circuitry?  Aside from not being able to make sense of the display, the computer appears to be working fine otherwise.  (It's a server.)

Of course, the easiest way to tell would be to try a different display on it, but where this PowerMac is located does not make that process easy.  And if I need to go through all I need to to get at it, and if it's not the monitor, well, then I'd like to have the parts on hand to fix the PowerMac's video circuitry (capacitors?) so I can go ahead and fix it one way or the other.

Thanks!

photo-cropped.jpg

 

Cory5412

Daring Pioneer of the Future
Staff member
Did you turn this computer on with a different monitor (or no monitor) and then attach this monitor?

If so: connect the other monitor back. This looks like a Macintosh Color Display 14-inch (M1212 IIRC) and those are a fixed-sync 640x480@67 display. This looks like what happens when the video port is outputting a signal this display can't use.

Or, if you haven't yet: shut the machine down, then connect the monitor, and turn it back on. It should automatically detect that his monitor is there.

 

dcr

Well-known member
Did you turn this computer on with a different monitor (or no monitor) and then attach this monitor?
I don't think so because I wouldn't have had a reason to, on either point.  It's the same monitor it's had for years.  I remember doing something on it a couple months ago and the screen was fine but the last time I used it, maybe a month ago, the screen was as shown in the photo.

It runs as a server 24/7 and I only turn the monitor on when I need to do something on it.  But I don't disconnect the monitor at all.  Just use the power button.  And that's worked without issue for years.

This looks like a Macintosh Color Display 14-inch (M1212 IIRC) and those are a fixed-sync 640x480@67 display. This looks like what happens when the video port is outputting a signal this display can't use.
Pretty sure it is a 14" display.  And I don't think I've ever even tried anything other than 640x480 on it.

And I'm pretty sure all the monitors on the desk nearby that I might have used with it are all 640x480, but I don't recall trying to swap out monitors because I can't think of a reason why I would have and also because the way the machine is situated, it is a royal pain to even try.

Or, if you haven't yet: shut the machine down, then connect the monitor, and turn it back on. It should automatically detect that his monitor is there.
I have rebooted it to no effect.  I am pretty sure I also tried shutting it down and then restarting, but I'll try that again this evening just to be sure.

 

Cory5412

Daring Pioneer of the Future
Staff member
Hm. yeah, that's a bummer then. It really could be either.

You'd know right away if you connected another monitor to the 8600 or that monitor to another machine.

If you end up finding that the monitor works fine on another system, the first thing I'd do is pop out the VRAM SIMMs if you have any installed and then reinstall them, perhaps dusting or cleaning the simms and sockets when you do, just to see if it's something you can repair with maintenance instead of having to do a recap or replace a component.

 

dcr

Well-known member
Following up on this, here is what I did last night . . .

1. Tried a different monitor.  No go.  Same problem with the other monitor.

2. Removed the VRAM SIMMs.  A light layer of dust but otherwise appeared clean, especially the contacts.  Cleaned everything anyway.  Also swapped the positions of the two SIMMs.  Still no go.  Same problem with the monitor.

3. Moved the VRAM SIMMs to the two empty slots just in case it was a problem with the sockets.  Still no go.

4. Replaced the VRAM SIMMs with a pair of VRAM SIMMs from another 8600, known to be working.  Still no go.

5. Put the original VRAM SIMMs back in their original positions because, at this point, why not?  Still no go.

Don't see any issues with the logic board.  No signs of leaking capacitors or any damage to any traces or anything.  No leaking battery.  No fishy odors.  There was a good amount of dust inside the machine but not excessively so.  I cleaned that out on the first go around.

I did install an ATI Rage 128 Mac Edition PCI card in this machine (discussed in another thread) and hooked it up to a VGA LCD monitor.  That worked without any problems.  Still, I would like to figure out, if possible, what the problem might be with the built-in video.  Kind of a waste to use the Rage 128 card in this machine.  It's a server, so basic 640x480 is just fine for the rare times I need to use the monitor.

Any ideas?

Thanks again!

 

beachycove

Well-known member
The vram is obviously good, then.

So, having wrestled mightily in the distant past with displays on an 8600/300, I'd now connect both monitors at the same time and see if I could troubleshoot the problem that way. I found my system to be very software reliant when using large screens like the 17" ColorSync, so perhaps there are also glitches with small ones. I would not have expected such behaviour with a  bog-standard 13" screen, but I suppose it is possible. 

You could also do the obvious and zap your pram.

 
Last edited by a moderator:

soviet

Member
Look some of your VRAM Simms are bad, i have exactly this issue a few days ago. The screen looked very similar to your capture.
Are you interleaving the Simms correctly ?, also you tried only adding 2 Simms and swapping them to check for a bad one ?.
 

LCARS

Well-known member
My 8600 had a similar issue a few years ago with a M1212 CRT. I tried several different repairs, one worked, but I don't know for sure which one.
Initially, the only way I could see was to use the composite out connection to a TV.

I replaced the VRAM, reseated the AV card, all the RAM, SCSI connectors, and reset the PRAM. It was initially still fuzzy so I left it unplugged for a month and when I got the nerve to try again, it was fine. This makes me think that it could be a capacitor that needed to be fully drained. I'm sorry that I didn't make a more scientific approach at the time. It would have been useful for posts like these.

I also use mine right now with a DVI Rage card and System 7 DVI drivers. Which OS are you running? You might try booting with extensions off. I have had issues in the past where OS 8.5 was looking for ColorSync/AppleVision/etc monitors via ADB, couldn't find them (none to find), and gave a wonky image until that extension was disabled.
 
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