Thread
Bondi Blue iMac Power Issue
As an aside... have you replaced the PRAM battery? iMac's, Powerbooks and Powermacs alike from this era can be a little fickle about this and refuse to boot with a dead or missing PRAM battery.
Take an insulated wire, connect one end to the grounded metal frame where the screws hold the CRT in to the plastic, then carefully insert the other end under the suction cup-looking rubber that covers the hole where the flyback wire goes in to the CRT. If it has a charge, you'll hear the discharge and may see the spark.
This was actually still on the Apple repair certification tests until just a few years ago...
To the above I shall ad, it is a good idea to unground yourself as you do it... stand in a plastic tote box or something or wear rubber soles. That way the easiest way to earth for that 20,000+ volts is definitely not going to be you lol
IT LIVES!!! Kinda.
The new-to-us keyboard we bought arrived last night, and today we took the iMac out of the closet and plugged it in. When we pressed the button it chimed and started making noise!
The monitor took its sweet time to turn on - when it finally did the computer was already halfway through a startup Disk First Aid check. Apparently the last time it was turned on before it died it crashed.
After I got to the desktop I started looking around in various folders. Everything was working well... and then it randomly shut down.
The screen distorted for a second before the crash.
And now it won't turn on again, even with the new keyboard. :'(
The monitor was a bit dimmer than I remember it being before it died the first time (though it was years ago so my memory might be faulty), and the entire time it was on I could smell that unused electronic dust smell. So, my question is... what now? We know that the iMac has the potential for life, but it's obviously still very sick. A thorough dusting is definitely in its future, that much I've decided for sure.
If anyone's interested, I was able to record the extensions popping up on the bottom of the screen and a bit of the desktop. The video is here.
(Yes, I was crying a little bit at the end. This small glimmer of life was so wonderful to see after all these years!)
The new-to-us keyboard we bought arrived last night, and today we took the iMac out of the closet and plugged it in. When we pressed the button it chimed and started making noise!
The monitor took its sweet time to turn on - when it finally did the computer was already halfway through a startup Disk First Aid check. Apparently the last time it was turned on before it died it crashed.
After I got to the desktop I started looking around in various folders. Everything was working well... and then it randomly shut down.
The screen distorted for a second before the crash.And now it won't turn on again, even with the new keyboard. :'(
The monitor was a bit dimmer than I remember it being before it died the first time (though it was years ago so my memory might be faulty), and the entire time it was on I could smell that unused electronic dust smell. So, my question is... what now? We know that the iMac has the potential for life, but it's obviously still very sick. A thorough dusting is definitely in its future, that much I've decided for sure.
If anyone's interested, I was able to record the extensions popping up on the bottom of the screen and a bit of the desktop. The video is here.
(Yes, I was crying a little bit at the end. This small glimmer of life was so wonderful to see after all these years!)
It kinda sounds like an analog board/PSU problem.
From what I've read, the tray loading iMacs were prone to flyback transformer failure (which could explain the dimmer than usual screen with the distortion). If I remember though, the more common failure mode is starting up normally, and then shutting down with a loud zapping sound when it tries to engage the CRT, never making it to the desktop.
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From what I've read, the tray loading iMacs were prone to flyback transformer failure (which could explain the dimmer than usual screen with the distortion). If I remember though, the more common failure mode is starting up normally, and then shutting down with a loud zapping sound when it tries to engage the CRT, never making it to the desktop.
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Whilst it is very common for flyback transformers to fail in trayload (and even slotload, but they usually fail elsewhere before the fbt has a chance) iMacs, the symptoms you decribe would sound more like failure of the PSU itself. The more common behaviour when the flyback transformer and/or associated caps have blown is for the machine to surge and shut off as soon as the CRT is powered up, sometimes on the sly or sometimes with a loudish zap and a flash even.
The dimness and distortion of the screen prior to the complete failure would seem like a product of insufficient current or voltage to the CRT, which could be explained by a failing power supply given it now fails to boot. That said, there is still a possibility that the analogue video circutry is at fault and that something was drawing excess power or shorted and blew a fuse or other component in the power supply creating the secondary issue. But the intermittent startup issues would point more to an actual power supply issue.
The dimness and distortion of the screen prior to the complete failure would seem like a product of insufficient current or voltage to the CRT, which could be explained by a failing power supply given it now fails to boot. That said, there is still a possibility that the analogue video circutry is at fault and that something was drawing excess power or shorted and blew a fuse or other component in the power supply creating the secondary issue. But the intermittent startup issues would point more to an actual power supply issue.
I'll replace the power supply when I get a chance, and check caps also. I'm thinking of taking some pics to show y'all, maybe you'll see something I missed. 
For quite a while before the computer died the first time it was taking several pushes of the power button before turning on normally (which is why the button was a suspect), but I do vaguely remember the screen barely shrinking being the first noticeable symptom. Mind you, I was 12-14 when that started so I could be misremembering. The poor thing sat in my closet for five years before I brought it out to resurrect it. I had to put it back after trying the experiment with a borrowed keyboard a while ago.
Speaking of keyboards, does anyone else find it strange that a keyboard we bought on eBay was able to start the computer when a known working keyboard couldn't? 8-o
The CRT did have some issues when I turned the iMac on two days ago - about a minute between the startup chime and the CRT actually turning on, and when it did work the screen was dim. The only noticeable distortion, however, was right before the computer shut off. And the entire screen changed shape. (I should try to recreate it with Photoshop, it actually looked pretty cool.)
Edit: What type of power supply should I look for? A quick Google search did nothing but confuse me... LOL
For quite a while before the computer died the first time it was taking several pushes of the power button before turning on normally (which is why the button was a suspect), but I do vaguely remember the screen barely shrinking being the first noticeable symptom. Mind you, I was 12-14 when that started so I could be misremembering. The poor thing sat in my closet for five years before I brought it out to resurrect it.
I had to put it back after trying the experiment with a borrowed keyboard a while ago.Speaking of keyboards, does anyone else find it strange that a keyboard we bought on eBay was able to start the computer when a known working keyboard couldn't? 8-o
The CRT did have some issues when I turned the iMac on two days ago - about a minute between the startup chime and the CRT actually turning on, and when it did work the screen was dim. The only noticeable distortion, however, was right before the computer shut off. And the entire screen changed shape. (I should try to recreate it with Photoshop, it actually looked pretty cool.)
Edit: What type of power supply should I look for? A quick Google search did nothing but confuse me... LOL
I beleive Revision's A though D iMac power supplies and analogue boards are intercompatible. It is rather an involved task to remove it, requiring you to take the top shell off the machine, and requires extreme care as there are components in the analogue board/power supply area that can hold a very nasty residual charge, not the least of which is the CRT. If you have a look on my blog you will find a detailed teardown procedure for a slotload iMac... Whilst they are a fairly different ballpark, I assume they sort of go together the same way discounting the lower section, but probably with some screws in different places.
As it stand, if you are tearing it apart down to that level where you have the high voltage side exposed anyway, it may very well be worth having a detailed look at the analogue and PSU board for burnt components, swollen or burst caps, split rectifiers, resistors or diodes etc... with the symptoms you describe, I would expect to see a popped cap somewhere. If you find ones with the ends bulged instead of flat, leaking, or burst, then you have quite possible sourced the problem. If the issue is glaringly obvious, a recap might be the better alternative, as a secondhand board is probably going to be a game of Russian roulette in itself. As it stands, in either case you need to remove the high voltage board/s for replacement or repair, so it doesnt hurt to give the current items a good look over and see if you can spot a repairable problem
Anyway, I look forward to some good news.
As it stand, if you are tearing it apart down to that level where you have the high voltage side exposed anyway, it may very well be worth having a detailed look at the analogue and PSU board for burnt components, swollen or burst caps, split rectifiers, resistors or diodes etc... with the symptoms you describe, I would expect to see a popped cap somewhere. If you find ones with the ends bulged instead of flat, leaking, or burst, then you have quite possible sourced the problem. If the issue is glaringly obvious, a recap might be the better alternative, as a secondhand board is probably going to be a game of Russian roulette in itself. As it stands, in either case you need to remove the high voltage board/s for replacement or repair, so it doesnt hurt to give the current items a good look over and see if you can spot a repairable problem
Anyway, I look forward to some good news.
Ouch... did a more thorough Google search and a G3 power supply isn't cheap! 8-o I'll say something in the Trading Post soon, but at the moment I don't have all the tools for a teardown handy and need to find out more about how to be safe around high voltage. I'm a bit paranoid after some less than pleasant experiences around CRTs.