What part of the iMac is on its way out now?

[LCGuy]

As some of you know, after a few months of rest, i got my tray load iMac 333 back up and going in April, and its been trouble-free since then. However, one thing i'm noticing is that some days when i go to start it up, sometimes the display takes a while to warm up. Like, i'll turn the machine on, and it will chime, and i can hear the HD being accessed, and the Mac sounds like its starting up as per normal, but nothing will come up on the screen until its well into the startup. And then its very dim and out of focus for the next 10 minutes or so. After its warmed up properly the display works fine...right now i'm typing this on the iMac, and the display looks fine. Its just when cold-booting it first thing in the morning.

Anyway, i'm wondering...what part do you reckon would be going out on this machine? An obvious guess would be either the analog board or CRT, or the flyback (which, as you know, is on the AB), but i'm thinking that there could be a remote possibility that the PSU may have something to do with it, if its weak. The reason for this is that last year when my Classic II died, at the first stage of its death, at startup it would do this exact same thing: It'd chime and boot as normal, but the display wouldn't come up until a good few minutes later.

Also, would you reccommend switching over to an external display now, or waiting until the internal fails first? Displays aren't at all a problem...i have a 1710AV i can easily plug into it if i need to.

 

[Cory5412]

Wow, that's never fun. Although, (I'd wait until it actually dies, but that's just me) you could do an interesting enclosure hack as a result of this.

 

[LCGuy]

Yeah..basically, if the analog board goes, what i'll do, is just leave it in its existing case and plug the 1710AV straight into it and be done. If the PSU goes out, then i'll have some fun.

 

[MacMan]

I would probably say it was the CRT that is on it's way out, although I'm no iMac expert. Could be a candidate for a case mod at some point in the future.

 

[chris]

Stick a LCD in it and use the video out to drive it.

 

[Dan 7.1]

no...this is a known problem with tray-load imacs. i can't remember what the exact cause is, but iirc its a little circuit board which controls the power to the CRT display, and if you replace the board it almost always fixes the problem.

i'll try to dig up some info later.

 

[Quadraman]

Time to start thinking about rehousing the iMac motherboard and using an external monitor with it.

 

[SiliconValleyPirate]

I have to say I've heard literally dozens of stories of iMac G3s losing the analogue board to old age and overheating. The problem with the analogue board going south is not only does the CRT stop working but the iMac won't power on either. You'd need to seek out a mod to use an ATX PSU with it or something maybe?

 

[LCGuy]

Thanks for your thoughts, guys. You'll be interested to know that i've actually got the AppleVision 1710AV plugged into it right now (its working fine, btw). Anyway, with the machine running on an external display, and the internal display in standby mode (since its not plugged into anything), the machine is running noticeably cooler...its been running for a good 3 or so hours now, and when i put my hand on top of the iMac it still feels cool, like as if it hadn't been turned on at all. Since the analog board is on its way out, and its now Spring (which means in a couple of months it will be Summer) here in Australia, i'm thinking of leaving it like this for now...as it is, with the iMac on the floor and the AppleVision hooked up and on my desk in the place where the iMac normally goes, its fine for now.

Btw, i must say...it sure is nice to be able to run OS X at 1280x1024 instead of the puny resolution of 1024x768 that i'm used to!

 

[Dan 7.1]

well yeah...those G3's put out next to no heat, in fact if you open them up you'll find that the heatsink is TINY! its amazing to me that it dissipates heat at all .

 

[LCGuy]

Yes, but remember it still has a hard drive, and a power supply, which generate heat.

 

[Quadraman]

My iMac 700 has those convection vents on the top and it gets extremely hot. I would have to guess that most of the heat comes from the CRT and power supply.

 

[tomlee59]

I would probably say it was the CRT that is on it's way out,

CRTs are glorified lightbulbs, so a delayed turn-on is not a CRT failure mode. A CRT dims over time (just like a lightbulb), or can go dark permanently (like a lightbulb). There are more subtle failure modes, to be sure, but generally speaking, most display failures are caused by things other than the CRT. If the screen ever displays something, then the CRT itself is the last thing I would consider. Sounds like an analog-board problem to me (possibly triggered by a flyback that is on its way out).

 

[equill]

As tomlee59 writes. A CRT is very much a case of 'Have power. Will excite the phosphors.' Everything else depends upon inputs from elsewhere. Rotated or non-rectangular display? Talk sternly to the yoke or bias magnets. Squeezed, undulating or quivering display? Interrogate the deflection circuitry. And so on. If warm-up time is unduly extended you have to suspect heat-sensitive components, needing time to rediscover their original values. Take your pick where these are to be found. Gives one a new understanding of Apple's (and other companies') "pluck'n'chuck" style of Service Source directions for repair.

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