You can make a difference in the Apple Support Community!

When you sign up with your Apple Account, you can provide valuable feedback to other community members by upvoting helpful replies and User Tips.

Looks like no one’s replied in a while. To start the conversation again, simply ask a new question.

User profile for user: pscheepe
pscheepe Author
User level: Level 1
8 points

Powermac MDD does not start anymore but the power button LED is lighting up when pressed

I just got a dual processor powermac MDD with the original 24” display and are in the process of upgrading it.

It has 512 MB memory and a Nvidia AGP graphics card with the Apple Power Display Port, an Adaptec SCSI adapter and 2 160 GB high speed SCSI drives which I think are mirrored.

I put in a 128 GB SATA SSD via a Sata to IDE adapter that has been set to master.

Yesterday I was able to start the machine and install Tiger on the SSD via the DVD drive. It worked fine and started up a couple of times even via the power button on the monitor.

However, today I could not start it again even if the power button on the machine and on the display light up when pressed, not even the fans on the power supply start.

The power on green lead on the power supply shows 5V but I still need to test all the other voltages, also opende the power supply to check if the fuse was blown but that was OK.

Tested the P Ram battery and that was dead so I ordered a new one which has not arrived yet.

have taken out all the cards and Ram and plugged it in one by one and reseated these.

I found a pinout and test sequence for the power supply on line and will start testing it.

Anybody any idea wher I should look further.

thanks in advance,

Peter.


Earlier Mac models

Posted on Jun 3, 2024 2:20 AM

Reply
Question marked as Top-ranking reply
User profile for user: Allan Jones
Allan Jones
User level: Level 9
72,284 points

Posted on Jun 3, 2024 8:25 AM

Fellow MDD owner here. This is not an uncommon issue as MDDs age.


—PRAM battery: A "New World ROM" PowerMac like the MDD that will not start with a dead PRAM batt in the cage may start with no battery in the cage.


—When the MDD was in its heyday, Apple had a tech article that said if the power button does not respond, try pressing it at the edge of its lower right quadrant. I used to have a screenshot from that article but it is apparently on my late-model MDD 1.25Ghz SP dual-boot, which won't start either. 🥴 (I have a donor MDD on hand, just haven't had the time to swap out parts).


—Another common issue was the front panel board (FPB), the card behind the power button bezel. Last I looked pulled FPBs were available, but the workaround device is even more available and cheaper. The original iMac keyboard, part number M2452, was the only Apple USB board to retain the keyboard-mounted power button of older ADB keyboards:



Apparently the power button on a working M2452 will override the power button on the G4 in the presence of a dead FPB. I've seen these for under US$5 at thrift stores, but you MUST get that specific model. One guy with whom it worked had a dead FPB in his MDD and picked up an M2452 and never replaced the FPB. After he started the computer each day from the M2452, he stowed the iMac keyboard between his tower and a vertical support on his workstation and used his newer keyboard.


—This amazing site by a former contributor here has power supply diagnostics for many PowerMacs including the MDD:


http://www.jcsenterprises.com/Japamacs_Page/All_Things_PPC.html


With a multimeter and his instructions you can do a full rundown of the power supply.


—While we're on power supplies, the MDD had two different versions. The first was a 400W model that was super-reliable but sounded like a flight of B-17 bombers taking off. Following many complaints, Apple changed to a quieter 360W model; unfortunately, it was not as reliable as the 400W "bomber simulator" PS. It might be nice to know which you have.


Open the side panel and you can usually see the sticker with the power rating on the side of the PS.


I'll be out much of today but will try to check back in tonight.


Allan




View in context
2 replies
Question marked as Top-ranking reply
User profile for user: Allan Jones
Allan Jones
User level: Level 9
72,284 points

Jun 3, 2024 8:25 AM in response to pscheepe

Fellow MDD owner here. This is not an uncommon issue as MDDs age.


—PRAM battery: A "New World ROM" PowerMac like the MDD that will not start with a dead PRAM batt in the cage may start with no battery in the cage.


—When the MDD was in its heyday, Apple had a tech article that said if the power button does not respond, try pressing it at the edge of its lower right quadrant. I used to have a screenshot from that article but it is apparently on my late-model MDD 1.25Ghz SP dual-boot, which won't start either. 🥴 (I have a donor MDD on hand, just haven't had the time to swap out parts).


—Another common issue was the front panel board (FPB), the card behind the power button bezel. Last I looked pulled FPBs were available, but the workaround device is even more available and cheaper. The original iMac keyboard, part number M2452, was the only Apple USB board to retain the keyboard-mounted power button of older ADB keyboards:



Apparently the power button on a working M2452 will override the power button on the G4 in the presence of a dead FPB. I've seen these for under US$5 at thrift stores, but you MUST get that specific model. One guy with whom it worked had a dead FPB in his MDD and picked up an M2452 and never replaced the FPB. After he started the computer each day from the M2452, he stowed the iMac keyboard between his tower and a vertical support on his workstation and used his newer keyboard.


—This amazing site by a former contributor here has power supply diagnostics for many PowerMacs including the MDD:


http://www.jcsenterprises.com/Japamacs_Page/All_Things_PPC.html


With a multimeter and his instructions you can do a full rundown of the power supply.


—While we're on power supplies, the MDD had two different versions. The first was a 400W model that was super-reliable but sounded like a flight of B-17 bombers taking off. Following many complaints, Apple changed to a quieter 360W model; unfortunately, it was not as reliable as the 400W "bomber simulator" PS. It might be nice to know which you have.


Open the side panel and you can usually see the sticker with the power rating on the side of the PS.


I'll be out much of today but will try to check back in tonight.


Allan




Reply
User profile for user: pscheepe
pscheepe Author
User level: Level 1
8 points

Jun 3, 2024 9:03 AM in response to Allan Jones

Hallo Allan,

Many thanks for your quick reply. I read one of your previous posts on this matter and from there I deducted that it might be the PRAM battery so I ordered an new one and you also pointed me to the site with poer supply pinout, thanks for that.

For as far as using the keyboard button, I assumed that this would work similarly to the power button on the display, which in my case did not work as well.

my PD is the 360W model by the way.

I will try your suggestion of pressing the lower quadrant of the FSB.

Anyway I will you posted of the results.

Greetings,

Peter

Reply

Powermac MDD does not start anymore but the power button LED is lighting up when pressed

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple Account.
Learn more Sign up