iMac G4; failing capacitors?

[jibsaramnim]

Hi all!

I have a gorgeous iMac G4 that I was able to find (with difficulty) where I live late last year, and I've been enjoying it a ton since getting it. I have replaced its fan with a Noctua one, upgraded its stock CD drive to a DVD one, and have a basic IDE to mSATA adapter in there to replace its original hard drive. Other than that, it's stock with no work done to it — well, other than a lot of elbow grease to clean it as best I can. Pretty sure the previous owner used it in a rather dusty and possible somewhat smoke-filled environment, judging by the dirtiness it had inside.

Last weekend I opened it up again as I wanted to apply fresh thermal paste on the CPU, something I didn't do last time around. I also took the opportunity to replace the conductive pads on the bottom of the motherboard. I felt like it may have been running a bit warmer than I'd like when playing through the Age of Empires campaign, which is what led me to do this all now.

This time while I was in there I noticed two electrolytic capacitors that have some light cracks showing, and near it some spools of some kind (apologies, I'm not an expert and lack familiarity with all the necessary lingo) have some edges clipped off too it appears. I am not too familiar with how these types of capacitors might show trouble as I've usually seen us replace other types with these . Do you think these are signs of them on their way to failing, or is it mostly just an aesthetic thing, or something else? I can't help but feel like these look like they may have some sort of plastic(?) coating on them as opposed to the other capacitors seen around these, they appear a bit more "shiny." I could be way off the mark here. I should have tried to make more photos while I was in there, I do hope the one I have is of some help already.

View attachment 20240623_DSC01465.jpg

The iMac is operating perfectly fine from what I can tell, with one exception that I'm not 100% sure is actually an issue or just how it always worked. The best way I can describe it is: when playing back audio over the Apple Pro speakers (though I believe the same happens with the tinny internal one), when only some softer sounds are playing you can hear there's a sort of cut-off level and some of those sounds are not played back, or partially played back in case there is a fade-in for example. It doesn't happen when it's actively playing back continuous audio that's above this supposed threshold, it really only happens with soft (or, at lower volume) individual sounds basically.

If it is an issue, does anyone happen to have a link to a site/thread that has more details on the iMac G4's components? I was so far unable to find a parts list.

Thank you kindly in advance for any tips or advice you may be able to provide!

 

[robin-fo]

Your capacitors are probably still fine and the broken bits of the „spools“ probably don‘t matter.

 

[QuadG5MacDan1138]

The caps look fine. The lines are just the scribes for bursting. If you want to replace them, go ahead, but G4 iMacs agent as prone to capacitor plague like the G5s. They look different from all the others because they are a different voltage.

The spools are inductors or chokes. The broken parts are the bobbin around which the metal coils are wound. They are also fine. They’re just acting as filters And their performance is not affected by this cosmetic damage.

 

[FoaRyan]

when playing back audio over the Apple Pro speakers (though I believe the same happens with the tinny internal one), when only some softer sounds are playing you can hear there's a sort of cut-off level and some of those sounds are not played back, or partially played back in case there is a fade-in for example. It doesn't happen when it's actively playing back continuous audio that's above this supposed threshold, it really only happens with soft (or, at lower volume) individual sounds basically.

From an audio-only perspective, it sounds like you're describing compression. Not as in mp3 digital compression but more like noise gating. If this were a guitar or guitar amp maybe cleaning the potentiometers would help, but I'm not sure what would cause it on a computer.

How low does the volume or sound have to be to get cut off? And if you turn the volume up, do the "low" sounds start to be heard? The nature of those symptoms might provide a clue.

 

[jibsaramnim]

Apologies for the belated response! Life got in the way.

From an audio-only perspective, it sounds like you're describing compression. Not as in mp3 digital compression but more like noise gating. If this were a guitar or guitar amp maybe cleaning the potentiometers would help, but I'm not sure what would cause it on a computer.

You know, this does explain it much better than I did. It sounds like if it has a cut-off filter that is set too generously, or it simply takes too long for it to get turned off when sounds need to be made heard.

How low does the volume or sound have to be to get cut off? And if you turn the volume up, do the "low" sounds start to be heard? The nature of those symptoms might provide a clue.

As the Apple Pro Speakers go ridiculously loud, I basically have the volume set real low in OS9 so that I'm not shaking the neighbours out of their beds. If I play something like Age of Empires or SimCity without background music and a character or event makes a sound, you can hear it effectively fade in, rather than just hearing the entire sound as it should be. I've also had a few cases such as with certain smaller, soft tunes that play at the beginning of certain tunes in SimCity 2000 where you can hear that as they're short sounds, it basically doesn't really get to play them out — or you just hear the tail end of the sound.

I don't have a recording of this as I've been busy with work things, but I hope my description makes some sense here. I was just wondering if this was how sound on these iMacs worked, or if mine in particular had a particularly overzealous filter (or slow capacitors or something else?) that causes this.

Thanks so much for sharing your thoughts on this!