G3-500 "Dalmation" with a screen flicker. Only happens at 1024 x 768 @ 75hz

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Joined: Jun 23 2007
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Hi all, newbie here.

I save the most immaculate G3 from being broken up for it's copper at the rear of the tube a few days ago. This thing looks like it just came out of the box! I was sitting on the ground (road) and when I asked the guy if it was a 500 he went to kick it over on to the tube front, lucky I grabbed it in time.

All that said it had 9.2 installed and only haveing a CD installed I loaded 10.1 onto it to have a play.

The only thing I can find wrong is it seems perfect at 800 x 600 @ 95hz but when you select 1024 x 768 @ 75hz the display gets quite a pronounced screen flicker. It did this on both 9.2 and 10.1. I suspect this machine has had little or no use due to it's condition and may have been sitting around for quite a while.

Has anyone seen this issue before?

All help appreciated.

Rod

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tmtomh's picture
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Joined: Dec 20 2003
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Are You Sure It's a Defect?

This could be a sign that the machine's analogue circuitry is about to go. But at the same time it might be just a combination of age and perception - all screens get flickery at refresh rates of 72-75Hz or below, and the amount of flicker depends on one's individual perception.

Also, the iMac had a CRT optimized for unusually high refresh rates (up to 117Hz or more) compared with other non-professional CRTs of the time, so it might just not look so great at a lower refresh.

Are you able to run it at 1024x768 resolution with a refresh rate higher than 75Hz? Is 1024x768@75 listed as one of the "recommended" settings, or as one of the "show all" settings in the Display Preference Pane?

It might just be that this hardware doesn't run well at that setting.

Best,
Matt

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Joined: Jun 23 2007
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Hi Matt, At 1024 x 768 the

Hi Matt,

At 1024 x 768 the only refresh option is 75, 95 and 117 are "greyed out". The flicker would better be described as a "shudder" with the image moving left to right and back slightly.

Rod

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I hate to say something

I don't mean to hijack a thread, but I was going to ask something along the lines of why CRTs shudder? Sorry, i didn't meant to take over (not my intent) but it would help if I know what causes this on my Sony Trinitron. it will suddenly start swaying to the left, back to the right, then repeat. It does this after a while, but it stops as suddenly as it begins. It's just odd, but does anyone know ANYTHING about trinitrons and as to why they do this?
It might help clear up the shuddering problem with this iMac.

The Screen works fine (as can also be told with this iMac listed above ^) and shows no sign of failure. I can only describer it as if the display was on water kinda bobbing and waving about. Just never seen it before.

Thanks for letting me use this thread, but I am pretty sure this goes along the same lines as my monitor, because we share something similair. I don't know that much about CRTs, so I figure if anything, this might help me Smile

I don't think your display is going out, as mine has lasted a while (over 7 years) and still does this.

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Jon's picture
Jon
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I'd guess the swaying would b

I'd guess the swaying would be voltage variations in the coils of the deflection yoke that make the beam sweep from side to side, or voltage fluctuations or spikes elsewhere that are interfering with it.

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If it were voltage related th

If it were voltage related then would the problem not occur at any res? Is there anything I can do to make 1024 x 768 available at the next refresh up which is 93hz? (greyed out option at the moment)

I would know how to do this on Linux or Windows but not on Leopard.

Rod

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a flyback that is starting to

a flyback that is starting to show signes of going out will also produce this effect on the CRT. if one is starting to go it will handle some screen resolutions but not the higher ones (which is why it might only do that in 1024x768).

you can take the AIO Mac's to a tv repair man and he can check things for you to see what's wrong with it and he can say what can fix it. most of the TV repairmen are great at tracking down problems like this cause for one they have the tool's to diagnose them and adjust them.

i have a few thing's going on with my internal CRT in my Beige G3 AIO i want one to look at and see if he can fix it.

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eeun's picture
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Dirty power

I have occasional issues with dirty power coming in from the mains, as well as interference from local devices. That could also be your culprit.

My basement 'lab' gets interference which causes monitors to warble in most resolutions, though the closer you get to 60Hz, the more noticeable it is, since the AC is a 60Hz cycle.

I also get a warble if I'm running a portable heater on the same circuit.

You might want to try a different house circuit, turning off air conditioning, etc. before ruling it an internal problem.

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Jon
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Yes, running large appliances

Yes, running large appliances on the same circuit is not a good idea. For one, when it kicks on it may brown out the power on that circuit and cause damage.

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You won't believe this, my fi

You won't believe this, my fish tank is on the same powerpoint I'm using and it's the flouro light causing the problem.

Thanks to all for suggestions as you put me on the right path.

Now, does anyone know how to install 10.4 from a DVD on this machine which only has a CD Rom?

Rod

Jon's picture
Jon
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Get 10.4 on CD. ;) It works

Get 10.4 on CD. Wink It works just great. If you happen yo have a USB DVD drive, you might be able to boot from it, or even a FW drive.

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i think the dvd can be split

i think the dvd can be split into 4 cd'd if you know what to put on each cd. that is is you have a burner on a Mac somewhere

i can tell you what's on the first 2 cd's.

i dont know if you can make them bootable or not but you can try

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Jon
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I think it may also be possib

I think it may also be possible to copy the files to a hard drive partition and run them from there. Overall an external 5.25" FW/USB enclosure may be better in the long run, and it will still be useful to hold an optical drive or anther hard drive after you're done.

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