I recently was given this Imac. the computer itself seems to work fine, but the screen has a weird issue. The right half of it is tinted green. This is not the result of a damaged shadow mask, because when I put a dark color on the screen, the tinting to the right of it goes away, or severely lessens. Take a look at the pic I snapped to see what I mean:

http://i119.photobucket.com/albums/o121/mrx3750/100_0063.jpg

I assume there's some electronic component that's drifted out of tolerance somewhere inside this thing.

000

This looks like poor low-frequency response in one or more of the R,G,B channels (note that the color is different to the right of the black rectangle). This could be in the video adapter of the computer or in the monitor video circuits - does the imac have an output for an external monitor you could try?

- does the imac have an output for an external monitor you could try?

No it doesn't, or I'd be using a better moinitor.

Guess I'll have to start checking caps...

The monitor output is in the back at the bottom under an oval cover with vents in it. You have to pry it off, there is a slot for a screwdriver. I know quite a bit about macs, I fix them all the time and use them too. I don't however, know what your issue is. My friend here at work has the same thing going on with his. But it belongs to the school so I never investigated it.

Well, I've already ripped away most of the plastic. Still need to get the see through blue cover off. It will never look the same after I put it back together, because the green plastic under the covering is ridiculously fragile. But whatever. I never did like how the Imac looked anyway. and it might not get so damn hot if the cover had a few more ventillation holes!

Is this a slot loading or tray loading iMac? I've never worked on a tray loader but I've disassembled several of the later slot loading iMacs, mostly to clean out the dust. Taking off the bottom to get to the motherboard is pretty easy, but taking off the top to get to the power supply and CRT is harder, there are those awful plastic tabs all over that you will end up breaking off most of them. I think the tray loading ones are more difficult to take apart. The plastic in these is notorious for degrading due to the heat, particularly the ribbed plastic that surrounds the screen, it has been cracked on severs of the ones I've worked on. The tray loading iMacs have fans, but the slot loading ones work with convection only, though I think there were some fans made that fit around the handle.

I replaced the flyback on a Rev. A tray-loader. Managed to do it without cracking the plastic :banana: but I came mighty close. I'd suspect caps because these things run HOT!

Also, I think the tray loaders are easier to take apart than the slot loaders. Getting to the PAV in my Rev. E slot-loader is a pain.

It's a slot loading imac.

I already KNOW I'm going to have to break that plastic cover to get it off. I'm fine with that, as I'll probably put on a cover with more ventillation anyway.

Okay, after breaking a few tabs, I have that damn blue cover off! After uncovering the CRT neck board, which is surrounded by metal and plastic, I've found that it has a LOT of Teapo caps on it, and I know Teapo is a bad cap brand...

I'm probably going to change out every Teapo cap I see, then put it back together well enough to power it up and see if the new caps help.

000

Well screw the cover for now. I've been testing caps on the CRT neck board. So far I've found at least two that measured low. One, a 1uf@ 160 volt measured with no significant capacitance whatsoever. So I think I've found the problem area, or at least one of the problem areas.

Now I just need to hunt down a 1uf @160 volt cap...

Okay, just about every capacitor on this CRT neck board has tested at well below its rated capacitance. I'm surprised the damn thing worked at all with all these bad caps in it.

you cant go by that half the time. you have to ESR test them.

it looks like the CRT may be burned in. its weird. shine a bright light at it and see.

I have the same exact imac, and the analog board is bad on it also. it works ok, but the picture starts to shrink as it runs for a bit. if you tap the board, itll pop back out. but if not, itll continue to shrink until it shuts down. it has to be a hairline invisible crack in the power supply or something, i hit up every single solder joint in the sucker.

you cant go by that half the time. you have to ESR test them.

it looks like the CRT may be burned in. its weird. shine a bright light at it and see.


Um, you DID see my image about where I showed that the green goes away whenever there's a dark color on the screen, right?

No, there is no burn in.

Also, they're Teapo caps, I already know they're bad. When a 100uf capacitor tests at only 35uf, I call it bad.

maybe so, but like i said, i would never go by that. unless you pull them out of circuit, then i would go by that. as theres other things in the circuit that will affect capacitance readings. everyone would tell you that. However. it wouldnt surprise me if it was the capacitors though, certainly looks like it might be the issue. hehe.

Bad caps can cause the problem he's getting. Caps that have lost most of their capacitance. Like the 100uf that reads 35. An in circuit tester won't likely be fooled into reading a good cap like that. Fairly common. Replace them all.

I should note that I pull *ALL* caps out of circuit before testing. Every component I test, I pull it out of circuit first.

That looks a whole lot like phosphor burn on the CRT. I've seen that where a program is left running and no screen saver used when the program is not running and its just left on

That looks a whole lot like phosphor burn on the CRT. I've seen that where a program is left running and no screen saver used when the program is not running and its just left on

Phosphor burn does not disappear when you draw a square next to it.

In the pic, you'll notice a black square, and to the right of that square the green tinting disappears. if I resize the square, the tinting changes.

Phosphor burn does not cause this.

The pic says it all:
http://i119.photobucket.com/albums/o121/mrx3750/fixedmac.jpg

Even though my camera tinted it blue, the image is not tinted at all anymore. It was bad caps.

hehe. now you need to throw OSX on that badboy, and get rid of the OS9 classic which you cant really do anything with.

hehe. now you need to throw OSX on that badboy, and get rid of the OS9 classic which you cant really do anything with.

No, not really. I only fixed this Imac for two reasons and two reasons only:

1: I worked with this same model and same OS9 back in highschool.

2: I wanted to play with Simpletext again.

Other then that I have no use for this thing, so upgrading it to OSX is too much of a hassle for me.

well if that was the case, there are free emulators out there, you could play with simpletext all day long. lol.

yea i remember OS9. i didnt start playing with macs until junior high, and it was os 7.5.5 running on old performa 5200/75s.

didnt start playing with macs until junior high, and it was os 7.5.5 running on old performa 5200/75s.

I used those slow POS'es back in Junior high as well.

I used those slow POS'es back in Junior high as well.

yeap. and all you could do was play with a program called At Ease. and then, you had to use the CCC program for math and crap.

Actually no, they could run Oregon trail 2... slowly.

I possess a couple of macs myself, a Performa 550 and a IIsi, both working, the 550 has a 10mbit ethernet card installed, so it can do internet access, albeit slowly.

I possess a couple of macs myself, a Performa 550 and a IIsi, both working, the 550 has a 10mbit ethernet card installed, so it can do internet access, albeit slowly.

oh boy. i would NEVER try to brows the internet on something like this. lol. considering all the upgrades websites have went through with scripting and stuff. it would choke that little 33mhz 68K cpu. literally. hehe, unless javascript and all that stuff was turned off, then it would be ok, but most websites arnt even browsable in that state.

however, it would make a great email machine. it can do that fairly well :-)

I have a mac color classic, which is a rare one. problem is, analog board is shot and i need a new one. it had a convergence issue, and overheated zeners. i removed and lost the zeners, so i know they are gone. and this board is toast.

We had these in elementary running OS 9. Memories...

I have a slot-loader too. It's loaded with G-Luxon caps. We'll see how long it goes before it starts acting up. It came with OS 9... the first thing I did was to put OSX 10.3 on it. Runs pretty decent, especially considering it's a 333mhz processor with 192 of RAM!

I left OS9 on the drive so I can switch between the OSes. OS X for playing music (its the only computer in my room), OS 9 for messing with the voice thing in SimpleText and playing Spin Doctor, Bugdom, Lode Runner, etc. etc. Check out Macintosh Garden (google it), they've got LOADS of old Mac games and most of them run OK in OS 9.

oh boy. i would NEVER try to brows the internet on something like this. lol. considering all the upgrades websites have went through with scripting and stuff. it would choke that little 33mhz 68K cpu. literally. hehe, unless javascript and all that stuff was turned off, then it would be ok, but most websites arnt even browsable in that state.

however, it would make a great email machine. it can do that fairly well :-)

I have a mac color classic, which is a rare one. problem is, analog board is shot and i need a new one. it had a convergence issue, and overheated zeners. i removed and lost the zeners, so i know they are gone. and this board is toast.

Actually it doesn't do too badly. It's homepage is set to the Macintosh Garden (an extension of the-underdogs.info's abandonware site)

When not online, it's used to play classics like Maelstrom, Spheres, Movod II, etc.

We had these in elementary running OS 9. Memories...

I have a slot-loader too. It's loaded with G-Luxon caps. We'll see how long it goes before it starts acting up. It came with OS 9... the first thing I did was to put OSX 10.3 on it. Runs pretty decent, especially considering it's a 333mhz processor with 192 of RAM!

I left OS9 on the drive so I can switch between the OSes. OS X for playing music (its the only computer in my room), OS 9 for messing with the voice thing in SimpleText and playing Spin Doctor, Bugdom, Lode Runner, etc. etc. Check out Macintosh Garden (google it), they've got LOADS of old Mac games and most of them run OK in OS 9.

Although it seems to be down as of this post, Macintosh Garden can be found at http://mac.the-underdogs.info/

I recently was given this Imac. the computer itself seems to work fine, but the screen has a weird issue. The right half of it is tinted green. This is not the result of a damaged shadow mask, because when I put a dark color on the screen, the tinting to the right of it goes away, or severely lessens. Take a look at the pic I snapped to see what I mean:

http://i119.photobucket.com/albums/o121/mrx3750/100_0063.jpg

I assume there's some electronic component that's drifted out of tolerance somewhere inside this thing.

I have seen this kind of issue when the videocard starts to go.
the key thing that indicates that to me is the way the black square has an effect on the picture.