PowerMac - resetting screen resolution without mouse HELP

[hillmanmac]

I hope someone out there can help me. I have a 6500-300 PowerMac. I stupidly reset the screen resolution to some Simulscan setting and can no longer reset it 'cos the screen is a total mess. I need to get back to the standard 640 X 480 using the keyboard as far as I can tell but have no idea how to do this. Help greatly appreciated

 

[jmgalvin]

If you start up from your software install CD, you'll have full access to everything. Just put in the cd & restart while holding down the C key.

You can try going to System Folder/Preferences and trashing Monitors. That might do it. Then try restarting, without holding down the C key, and see how the monitor looks. if, by some chance yur machine stills starts up from the dc, go to the Apple menu and click on Startup disk and select Hard Drive..

When thing get real bad, it's sometimes easiest to just do a Clean Install of your System - leaving you old system folder, and all the stuff you want from that in a new folder entitled Previous System.

To doa clean install of system software, start from cd & go to Install, On the first or second screen, you should see something like Options. click on that and select Clean Install. DO NOT do a regular install or you'll loose stuff. Make sure you do a CLEAN INSTALL.

When done, restart. You can then move stuff you want to retains, like special Control Panels, Extensions, Fonts from Previous System fodler to System Folder. Just open something like Extensions in both Previous System & System folders. Put them in List view and compare. Drag things that you don't see in the new folder from the earlier one.

 

[hillmanmac]

Yeah. That's what I thought would do the trick. Whenever I've had a problem before the Restore CD has got me out of trouble. This time it doesn't work. The screen is still a mass of horizontal flickering lines and I can't see the mouse pointer or anything recognisable. But you can tell that the CD has booted up because the colour of the screen changes from a normal restart.

 

[jmgalvin]

That does NOT sound good. Something is not getting to your video signal I had a similar problem with an iMac - the horizontal flickering lines moving up or down at startup - very quickly, sort of like the Horizontal control on old tvs being out of wack. I found that, if I let it go for awhile - a long while - the screen finally came alive ok. I just let it sleep after that, rather than turning off.

You might try zapping the PRAM - restart holding down Command, Option, P & R keys until you hear a second tone. Or try starting up with Extensions disabled - hold down shift key immediately after tone.

You could also try plugging in another monitor to see if the monitor gave up the ghost. Then again, your machine is certainly not new, you could have some internal prblems. 800 dollars gets you a new eMac. Less if you buy a refurb from the Apple's online store. It's a nice machine. We have a bunch of them in our office. You just have t add 512 megs of RAM to get them humming.

 

[ObviousTroll]

I also recommend zapping the pram. I seem to remember that older Macs had some video info in there.

You may not be able to erase the PRAM by pressing Command,Option,P&R however - that only works for newer Macs.

IIRC, older Macs had different ways of doing it - but I googled around and couldn't find it.

 

[pixl8r]

Command, Option, P & R works for all Power Macs and even many pre-Power PC macs.

As I recall it does reset the resolution in your case probably to 640x480. Hold down the key combination until you have heard the boot chime 3 times then release.

Hope it helps.

Wow JT that almost looked like you knew what you were doing!

 

[hillmanmac]

Thanks all you guys. Zapped the PRAM and got the smiley icon followed by the Welcome screen and thought 'its fixed'. Dismay when after about 5 seconds the screen returned to a mess of lines just like before. Any other strategies?

 

[jmgalvin]

Got another monitor you can plug in - just to check? Also unplug the monitor from the computer and then plug it back in. Also you could try leaving the monitor on for a while - in case a capacitor is actiing up till it stabilizes.

You can go through the other mac fixits: Start up with extensions off - hold down shift key. Rebuild desktop - hold down command & option keys while starting

Try leaving the thing on for a long tme & see if things happen to straighten out.

If the thing is all scrambled when booting from cd, there seems to be problem in the machine or the monitor. When you boot off the cd, your monitor settings are not used, nor are any of the other system settings.

 

[pixl8r]

You could pull the battery on the mother board. That will definitely get rid of all saved system settings. I'm not sure how long you need to leave it out though. Maybe an hour or two (or more) and make sure you unplug the CPU.

Wow JT that almost looked like you knew what you were doing!

 

[eaglefan2000]

You could try installing a new system from the install cd. Choose install fresh system I think is what you need. All it will do is install a new system folder and name your old system folder something else. When you have it up you can move over extensions and prefs you need or just rename the new system and name the old system back to system folder and restart to start over again..

Joseph Kunder
Technical Systems Specialist

 

[hillmanmac]

Thanks to all
I finally fixed it by Zapping the pram at restart with the restore disc in place and during the few seconds when the smiley icon was on the screen restarted from the CD. This was Ok until the end of the restore process and I retarted the machine and the screen went bananas again. So I had a go at the same process but with OS8 base operating system disc and then was able to re-intialise the hard drive. Then I used the restore disc to get the s'ware up again.

It seems to me that there must be a few bytes on the HD that control the screen and the first thing that happens after start-up with zapped pram is that the HD puts them straight back into it. Anyway, it works.
Cheers