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Old Aug 23, 2011, 09:04 PM   #1
ethan86
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Power issue MDD Power Mac G4 (Bad PSU?)

I have a Power Mac G4 MDD model I've been working on recently that I have noticed a strange power issue with. It powers up and shuts down alright, but will not power up again unless I unplug it from the wall and plug it back in or flick the on/off switch on the power strip I have it plugged into. I changed the system battery and power cable, which made it work fine last night, but when I tested it today, I encountered the same results I had prior to the battery/cable switch. I'm beginning to wonder if the power supply is going bad, which would kill the plans I had for it. Has anyone run into an issue like this before? Is it something I can fix cheaply or will I have to buy a whole new power supply?
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Old Aug 23, 2011, 09:09 PM   #2
MrCheeto
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Tell us what happens once you reset the PMU.
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Old Aug 23, 2011, 09:30 PM   #3
ethan86
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I actually did that yesterday, but honestly can't remember if it was before or after I put the new battery in. Will do it again, now.

----------

Resetting the PMU didn't help.
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Old Aug 23, 2011, 10:33 PM   #4
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If the PMU reset doesn't help, it is most likely the Power Supply. As you probably know, they're inherently flawed.

I'm offering free MDD Power Supply replacement, if you're interested. Catch it on my blog.
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Old Aug 24, 2011, 07:24 PM   #5
ethan86
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I'm offering free MDD Power Supply replacement, if you're interested. Catch it on my blog.
I think I will take you up on that offer. Send me your shipping information and I'll try to get that mac out to you by the end of the week.
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Old Aug 24, 2011, 07:56 PM   #6
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I think I will take you up on that offer. Send me your shipping information and I'll try to get that mac out to you by the end of the week.
Remove the power supply and save a bundle on shipping. Unless MrCheeto needs the whole thing for his blog project.

I wholeheartedly agree that this is a PSU issue.
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Old Aug 24, 2011, 08:00 PM   #7
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The PSU only weighs approximately 5-6 pounds.

Not only that, but I'd like to take a multimeter to it to be certain or all is wasted. In the end, if it turns out to be the power supply, I will need to cut the leads from the original PSU to preserve the cable-layout.

I shipped a PowerMac Blue & White for about $55 I think.

Along the same lines, you could remove the hard drives and optical drives and cages. All I need is the GPU and RAM to test the thing. I have hard drives of my own, of course.
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Old Aug 24, 2011, 09:27 PM   #8
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mr. cheeto, I hate to give to the run-a-round like this, but I think I am going to have to decline your offer. If I'm going to be purchasing a power supply anyways, I'd rather put it in myself. I appreciate your offer (honestly), but I'll be able to remove and install the power supply myself. For some reason after I read your post from last night, I was under the impression that you were going to repair the PSU itself. My brain hasn't been ticking right this evening (it was a long day at work). Again, I appreciate your willingness to help and am sorry to have given you a run-a-round like that.
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Old Aug 24, 2011, 09:29 PM   #9
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No problem! Again, it's just for the blog, not business :P
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Old Sep 10, 2011, 02:20 PM   #10
ethan86
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Update: About two weeks ago I bought a replacement PSU off ebay and installed it this past weekend. The MDD works great now and sounds a lot quieter than with the other power supply.

I have been wondering about one thing since buying the MDD last summer; when I turn it on via the tower's power button, I can't press the button dead center, I need to press the left half to power it up. Is this normal for the MDD? The guy I bought it off said he never turned it on via the tower, he always used a studio display.
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Old Sep 10, 2011, 02:58 PM   #11
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... and sounds a lot quieter than with the other power supply.
Nice! Sounds like you got one of Apple's quieter replacement units. Or maybe someone changed out the original fans.

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I need to press the left half to power it up. Is this normal for the MDD?
I have a couple that behave in slightly different ways. Probably nothing to worry about.
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