iMac G3 power supply noise

Discussion in 'PowerPC Macs' started by bigskymusiclove, Jul 4, 2013.

  1. bigskymusiclove macrumors newbie

    Joined:
    Jun 14, 2013
    #1
    Greetings, been making some progress on my Rev B iMac, I got the fly back replaced successfully, was a pretty easy job. The unit also has a bad CD-ROM drive, a replacement is on it's way.


    I still have the problem, when the unit is plugged in and turned off I can hear a high pitched whine, but when you turn the unit on, the sound go's away. Is this normal or is something getting ready to die?
     
  2. Graveyard macrumors regular

    Joined:
    Jul 29, 2009
    Location:
    Romania
    #2
    I think you'd better start replacing the capacitors before the thing breaks down. I am going to do the same as soon as i get the time, on my slot loading iMac G3. If those capacitors start acting up, they might damage other components in the power supply, and believe me, it's not easy repairing a power supply, especially if you can't find the adequate replacement parts.
     
  3. bigskymusiclove thread starter macrumors newbie

    Joined:
    Jun 14, 2013
    #3
    Thanks for the info, I was thinking the same thing, it's gotta be caps.

    Geez these iMacs seem to have a whole bunch of problems. They don't seem to be very reliable.
     
  4. Graveyard macrumors regular

    Joined:
    Jul 29, 2009
    Location:
    Romania
    #4
    Dude. They are pretty old machines. More than 10 years old. How many 10 years old wintels have you seen in working condition lately? These iMacs are reliable machines. I've had one running almost 24/7 from 2002 to 2005. I still have the darn machine and it still purrs like a kitten. But i remove power from it whenever i don't use it, so i don't kill the power supply for nothing.
     
  5. Andropov macrumors regular

    Andropov

    Joined:
    May 3, 2012
    Location:
    Spain
    #5
    That iMac is more than ten years old. Capacitors, the components that are probably failing right now in your power supply, have a life expectancy and don't work forever. That's why even the most reliable machines Apple has ever released will undoubtedly fail soon or late. Now, after ~25 years, the capacitors inside the first Macintoshes (128K, 512K/Ke, Plus, SE...etc) are starting to fail (all of them) nowadays. If you buy one of those classic AIOs today, you'll get the impression that they weren't very reliable. But actually they were. Components in all computers fail. Capacitors are usually the first ones.

    Apple usually uses high-quality components, even in capacitors (that's something people tend to forget when they look at the specs). PCs usually don't, and even when the power supplies inside them are fan-cooled and should have a better life expectancy because components are cooled, they don't.

    Back to the topic, you can take the power supply out of the iMac, insert a clip connecting GND (ground) and PowerON to make a bridge and then connect the power supply to the AC plug. It isn't dangerous if you do it well, just don't touch anything while connected to AC. That might help you to found the dead capacitor or the failing component, although if you have the necessary skills (it's easy) I'd recommend to recap the whole power supply. The life expectancy of the capacitors is rated in hours, so if one capacitor has failed, probably the nearby similar one's are going to fail soon too, even if they don't look damaged.

    It's important to do it, because if the power supply fails, it may fry all the other components in the line. For example, if suddenly the PSU seeds just 3 or 4 volts in the 5V line (or any other), more things will fail. The same if the 12V line suddenly becomes a 18V line. I wouldn't take the risk. Actually, it could have started. Did you know why the CD/DVD drive died? It could be because of the power supply giving a wrong input. Same for the fly back.
     
  6. bigskymusiclove, Jul 10, 2013
    Last edited: Jul 10, 2013

    bigskymusiclove thread starter macrumors newbie

    Joined:
    Jun 14, 2013
    #6
    Graveyard: A 10-15 year old wintel PC that won't power up is a hunk of junk and is very rare. I deal in a lot of computers 100's a year. I have seen countless computers that are 20-25 years or older take off an run just fine.

    Heck every Packed Bell I have run across runs just fine. Case in point of my vintage gaming system is a Gateway 2000 486DX2 66Mhz from about 93/94 still runs flawlessly.

    Keep in mind I don't expect anything to run forever, and have no problems in fixing things, but that iMac seems to a cascading failing pile of parts. I moved it out in the shed, it's fate will be decided later.

    Apple has just as many problems with stuff as a PC, G5 LCS, Bad caps in iMac and eMac's, bad flybacks in iMac g3's. The Quicksilver 733Mhz desktop I have seems to pretty good system so far, and the 1Ghz eMac.
     

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