g3 trayload 333mhz

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Joined: Feb 15 2007
Posts: 66

A grape 333 trayloader, worked fine for years. Then this weird electrical surging sound started happening. Youd be using it and ZZZZZZZZZZZAP! it make this noise and the screen would flicker. Used to happen once a week, then once a day, then several times in a day. Started keeping it off when not using it. Still worked great for games and internet for about a year. Then it did it one time and crapped out. System died, could not boot from keyboard or power buttons. No lights. Nothing. My question:
Is it a failed power supply, or some sort of more serious issue?

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Joined: Dec 19 2003
Posts: 6
g3 trayload 333mhz

Sorry to say, but imacs have a congenital defect with the high-voltage power supply (specifically, the flyback transformer is under-designed). The zzap noise and flickering was a sign that the flyback was starting to arc over internally. Now it's got a permanent short, which overloads the power supply and causes it to shut down as a self-protective maneuver. In serious cases, it even damages the power supply.

Replacement flybacks are not cheap, unfortunately. And organ donor units with good flybacks are rare -- the nonworking ones you come across frequently have the same problem yours does.

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Joined: Feb 15 2007
Posts: 66
does the donor have to be a t

does the donor have to be a tray load as well, I have a power supply from a g3 slot load, i think its 24 pin...

gobabushka's picture
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Joined: Apr 26 2004
Posts: 494
you could make the atx conver

you could make the atx conversion

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Joined: Feb 15 2007
Posts: 66
is there a place i can look t

is there a place i can look to see what the atx conversion is?

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Joined: Dec 19 2003
Posts: 1891
Re: is there a place i can look t

brulaheliko wrote:

is there a place i can look to see what the atx conversion is?

Forum search! Wink

There's a thread Here that not only has a good discussion, but links to several excellent conversion tutorials as well.

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Joined: Feb 15 2007
Posts: 66
right...guess I didnt think o

right...guess I didnt think of that. also checked out xlr8, had some neat info. Still I think the ATX conversion is my last choice for ressurecting my machine.
Is the Power flyback on the logic board, or on the power supply? Could one use a flyback from a slot loading iMac?

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Joined: Feb 15 2007
Posts: 66
actually I found (BY MYSELF,

actually I found (BY MYSELF, IM A BIG BOY. YAAAY) some more info. Found a company called bluestar sells them for about $30.00 and found some stuff on how to replace it but it sounds kinda sketchy. A page said that I could just hook up an external monitor to it. Is that a possible option in this case? Is there a way to find out if the power supply was toasted by the flyback failure, short of replacing the flyback and then see?

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Joined: Dec 19 2003
Posts: 6
toasted ps

One easy method is to remove the flyback. If the iMac can start up, then you know that the power supply survived unscathed.

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Joined: Feb 15 2007
Posts: 66
well thats better than replac

well thats better than replacing it, but Im scared of High Voltage, (I got kids now) I may just give up on this until I find an external monitor with the apple connector, or one of them adapters...