PowerMac G4 (MDD) won't turn on - HELP!

Resetting the Logic Board

Resetting the logic board can resolve many system problems. Whenever you have a

unit that fails to power up, you should follow this procedure

before replacing any modules.

1 Unplug the computer.

2 Press the Power On button on the front of the unit.

3 Open the side access panel.

4 Remove the battery from the logic board.

5 Wait at least 10 minutes before replacing the battery.

6 Make sure the battery is installed in the correct +/-

direction.

7 Reassemble the computer and test the unit.

Note:

This procedure resets the computer’s PRAM. Be sure to

check the computer’s time/date and other system parameter settings

Power Mac G4: Computer Does Not Power On, No Fan Movement

http://docs.info.apple.com/article.html?artnum=95038

 Cheers, Tom 😉

I'd try unplugging/replugging the power supply's Molex connectors that connect to the logic board. With older electronics, sometimes simply reseating connectors makes a difference. But your power supply might've given up the ghost, too. One source is www.dvwarehouse.com/G4-Power-Supply-c-247_476.html.

I had the same symptoms as you're having on my MDD 1.25 a couple of months ago. Went through all the possible culprits that you did...resetting pmu, removing/reinstalling ram, removing battery and disconnecting the powersupply from the main board, booting with the adc monitor detached, leaving it unplugged for days...etc. etc. nothing worked.

I ended up getting a refurbished psu off of ebay and that was the problem for mine. The one I got was ~$85 shipped to Hawaii but I've later seen refurbished ones for as low as $30. I was on the fence about parting it out or fixing it too.

Good luck and hope you get it worked out.

Can you check the voltages on the PSU?

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

You can convert an ATX PSU to use in an MDD...

http://jimmykirk.com/?p=34

I have all the same issues as described by Tanner, and have done the same.

Has anyone tried New or Refurb MDD power supply or logic bd and gotten anywhere?

It would all depend what is wrong, if it is one of those items that is defective, then there are many reports of replacing them curing the problem... but it caqn be so many things with MDDs.

i have the mdd 1.25 and one morning i turned it on and went to shower. came out and it was dead and my modem had restarted so i assume the power went off or surged. computer didn't do anything when i hit the button. i bought another one just like it for $100, pulled the hard drive and ram and put it in the newer one and all is well. now i am running two hard drives and have the older one for parts. i am suspecting the power switch is bad though because the newer one is so easy to turn on. i had to push the button just right and hard on the older one. j

While I have never owned a MDD, I did encounter the same issues with a QuickSilver a few years ago. Also purchased from eBay. Running in the pictures, and asured to run just the same when it arrived.

http://www.everymac.com/systems/apple/powermac_g4/specs/powermac_g4_733_qs.html

In the end, it did turn out to be a faulty power supply. While I would have loved to sink the money into the fix, I had a back Digital Audio Dual/533 that seemed to out pace the Quick in every way, so I ended up selling it on Criag's List for parts. I don't know if this will help. But I would be willing to say it's the PSU, if you can find one for a reasonable price, and if this is your primary mac it might be worth the money.

~Drake

hey seems like a common problem with this G4!!! cross finger my Gigabit ethernet G4 never got that symptom...

didn't see that thread so I did my own...

https://discussions.apple.com/thread/4043844

basically I thank everyone for the info I'm trying everything possible

actually texas man for me your info from the apple knb has gotten me back to the no power and just fast light when pressing the power button

I did what people told (see my post) to remove the cooler plate from the processor and restart without it! this is a great stuff it works any time! but then I'm still stuck with no image and red light on the motherboard with no little fan turning

the strange stuff is when pressing Shift + power when switching off the comp the actual small fan attached to them motherboard is turning so their is something that doesn't its job.

I tried another proc but nothing, another vid card nothing...

cheers

helllo all

fortunetly I haven't bought a new power suply did the voltage test and it's in perfect working order the logic board is obviously dead

cheers

Try hot wiring it and leave it on all the time or plug it in to turn it on, unplug to turn off. J