G4 MDD — won't start — power supply or logic board?

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G4 MDD — won't start — power supply or logic board?

G4 MDD — won't start — power supply or logic board?

Model: Power Mac G4 Mirror Drive Door, 2003 3,6 MDD Dual 1.25 GHz

M8570

How can you tell if it is the power supply versus logic board? I would like to purchase necessary parts but I don't know how to rule one

out over the other. I'd prefer to buy one part instead of a logic board and a power supply to find out it could be something else like
the Graphics card.

Description of Problem

My G4 MDD 2003 will not boot up. I was in the middle of using it when it froze. I hit the power button to force a shut down. It will no longer reboot.

There was no smell or smoke like some said they experienced from a blown fuse or capacitor failure in the power supply.

My model does not have a light on the logic board - so I cannot tell if the logic board is getting power. Most posts suggest it could be the battery - I replaced it. Other posts: it could be the power supply - but my power light comes on it just won't stay on or boot. It could also be the logic board - but i do not see signs of overheating. It felt warm but not hot on the power supply.

Before it froze :

I Ran Disk utility and changed permissions. I was working in an app then an hour later it froze. It had been keeping the time fine

as I had replaced the battery within the last year. I did buy a new 3.6 v battery just to be sure.

I did the steps that Apple provided for this issue.

Things I tried from other posts:

• New 3.6 Battery. No boot

• PMU reset. No boot.

• tried removing all ram, graphics card, and HDs one by one; still no boot.

• tried reseating dual processor - doesn't look fried.

• looked at the Logic board & doesn't look fried anywhere.

• tried to boot machine w/ and without battery. no boot.

• tried to make a different drive the boot drive by switching master / slave option on HD. still no boot.

Symptoms:

No Fan / No Chime / Nothing on screen

My thinking was If it is the power supply then it would not light the power button at all. When I unplugged the computer to discharge it by pressing power

with the battery in the power light isn't lighting up. So does that mean the logic board isn't getting power?

Thank you for your time and help.

PowerMac, Mac OS X (10.4.11), G4 Mirror Drive Door 2003

Posted on Oct 22, 2014 11:22 AM

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Answer 1

BDAqua

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250,259 points

Oct 22, 2014 11:41 AM in response to G4 MDD user

There are several voltages supplied by the PSU, only 5 VDC is needed by the power button I believe, also, there should be an LED lit on the Logic board if connected to power as I recall, but it's been ages since my 3 MDDs died.

Do you have a meter to test the MDD PSU?

http://www.jcsenterprises.com/Japamacs_Page/Blog/D275729F-09DA-4FBB-96B3-BEEEB2C 04619.html

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Answer 2

G4 MDD user Author

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Oct 22, 2014 12:05 PM in response to BDAqua

Thank you for your quick response. I do not have a meter. Where exactly is the LED light?

Would that mean a fuse is blown— because the power light will come on but not the whole device?

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Answer 3

BDAqua

Level 10

250,259 points

Oct 22, 2014 12:22 PM in response to G4 MDD user

There should be an LED lit...

G4 MDD won't start after a power outage

If a fuse IS blown it likely means a bad component in the PSU, the PSU provides many different voltages, only one needed for the power button, but all needed to run the Mac, still doesn't tell us if the problem is PSU or logic board, but I suspect the PSU.

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Answer 4

G4 MDD user Author

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Oct 22, 2014 12:52 PM in response to BDAqua

Can you tell me where that light is located or show me a pic of its location?

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Answer 5

BDAqua

Level 10

250,259 points

Oct 22, 2014 1:33 PM in response to G4 MDD user

I cannot, nor can I see it in a very poor picture of the logic board, nor have I found mention of it in the manual, but there may be help with this...

http://tim.id.au/laptops/apple/powermac/pmg4_mir_fw800.pdf

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Answer 6

G4 MDD user Author

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Oct 23, 2014 5:39 PM in response to BDAqua

I had followed the instructions from another post yesterday where you:

1. verify outlet is good - check. no boot

2. replace power cord - check. no boot

3. reset the logic board - hit PMU button see above - check. no boot.

4. check voltage on the power adapter connector

5. Disconnect all external devices, including monitor, and start up computer - check . no boot

6. Remove internal cards and start up computer

- ram - no boot

- pci - no boot

- graphics - no boot

7. Disconnect HDs 1 by 1 and restart the computer - no boot

8. Reseat the DC to DC board in its connector

9. Check the modem connector- if it has bent pins, replace the logic board

10. Replace Logic Board

It booted twice but only while I pressed the power button; then it immediately shut off. The fans came on, the red light on the inside on the logic board lit up, and then i got 1 long beep ( because I took out the ram 1 by 1 to to check it; then reseated it - i can't hit command option p-r while keeping power button pressed ).

Does this rule out the power supply. If that were a blown fuse it would not come back on. If it is a short then maybe it would.

If it is the processor wouldn't that be permanent and not come back on? Ditto the later with the logic board.

Any help is appreciated.

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Answer 7

BDAqua

Level 10

250,259 points

Oct 23, 2014 6:23 PM in response to G4 MDD user

I doubt it'll work, but try CMD+s while you hold the power button.

Maybe try this, pull the power cord, pull the battery out, hit the power switch to discharge, plug in AC power but not battery, try starting...

http://hints.macworld.com/article.php?story=2005040811124189

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Answer 8

kahjot

Level 4

2,463 points

Oct 24, 2014 12:05 PM in response to G4 MDD user

My suggestion would be to check eBay auctions or the LEM Swap List for your MDD model, and try to acquire a working one. You would probably pay about the same for the whole thing as you would pay for a PS or logic board. You can either scavenge the new one for its parts, or migrate your existingdrives and RAM into it.

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Answer 9

BDAqua

Level 10

250,259 points

Oct 25, 2014 11:11 AM in response to kahjot

Good point & suggestion. 🙂

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Answer 10

theulli

Level 1

11 points

Jan 25, 2015 7:04 AM in response to G4 MDD user

Hi

How did you get on?

My G4 just started off by switching off of its own accord and now when I press the power button it tries to start up but won't get far any more and dies. I. e. it doesn't get to click that you hear when it boots up any more now. Ist that the psu? I tried resetting the PMU and no luck. It's my recording device and the centre piece of my studio so I really want to keep it going.

Also, do you know where you can buy a new psu for this G4 mdd? Mine is a 400W.

Many thanks,

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Answer 11

theulli

Level 1

11 points

Jan 25, 2015 7:10 AM in response to theulli

Hi again,

Just to add, it just powered up, and the red light on the motherboard lit up, but cut out again after a minute or so.

Any advice is appreciated.

Many thanks,

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Answer 12

BDAqua

Level 10

250,259 points

Jan 25, 2015 10:57 AM in response to theulli

Hello,

Have you blown the dust out lately?

Especially the PSU, CPU heatsink, fans, & Video card?

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Answer 13

theulli

Level 1

11 points

Jan 25, 2015 11:19 AM in response to BDAqua

Hi,

Yes, it's pretty clean in there unfortunately. I might try the psu unit switch. It looks a bit of a hassle switching the atx (free from a friend) for apple mdd but worth trying, I suppose.

It's only 300w as opposed to the existing 400w, will this make a big difference?

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Answer 14

Drew Reece

Level 6

10,684 points

Jan 25, 2015 11:37 AM in response to theulli

The supply need to be capable of powering everything that you run. If you have filled the G4 with HD's, extra PCI cards, DVD readers etc the 300W supply will be underpowered & may overheat or cut out.

If you only have one HD powered up & the standard graphics card with no other loads you may be able to run it, but I wouldn't use it permanently I would use it as a quick test only, it could still kill the supply though as the startup load can be large.

These G4's also use custom wiring on the ATX connector, so you can't just shove a PC supply in & have it work…

http://www.applefritter.com/node/23857

http://atxg4.com/mdd.html

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