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Yiannis Author

Level 1

99 points

Power Mac G4 MDD strange startup problem

Hello ,

I have an old G4 MDD dual 1Ghz which is been used by my 6 years old son for gaming and watching movies.

I had Tiger 10.4.11 on a IBM deskstar HDD and Leo 10.5.8 on a seagate HD.

Everything was fine until some days ago, when my mac didn't boot from the first try…..black screen.

After a second attempt , booting was just fine.

I have now two system disks (IBM deskstar HDD) with 10.5.8 installed.

Mac is not booting always from first attempt….it takes two more with or without the option key pressed to choose a startup disk.

I have done all the usual…….reset PMU-PRAM…replacing battery,replacing cables,cable select the drives and now forced one to master and second to slave.

I have run Service Diagnostics 2.1.5………..ALL TESTS PASSED.

Still not booting normally….

Any suggestions please??

Thank you all!🙂

PS:It is also loosing very often internet connection via ethernet……..I think it's not a router problem as all my other macs are working normally.

PowerMac, Mac OS X (10.5.8), 2g Ram-1GHZ MDD

Posted on Oct 6, 2014 10:24 AM

75 replies

Yiannis Author

Level 1

99 points

Oct 22, 2014 1:24 PM in response to Yiannis

There is a short clip of the startup process ,if it helps...

ht tps://www.sendspace.com/file/3eij6k

BDAqua

Level 10

239,759 points

Oct 22, 2014 1:40 PM in response to Yiannis

To see the clip it wants me to install something. 😟

I can't read the most important last lines of the last Verbose screen.

Yiannis Author

Level 1

99 points

Oct 23, 2014 9:24 AM in response to BDAqua

Try this one.

https://www.sendspace.com/file/dsw9x6

Today I pushed the startup button and it does not startup so I checked the PSU again.

12+14 pin=+25V OK

12+1 pin =+5V OK

12+24 pin =+12V FAILED tried several times but I can't get that reading.

Strange thing is that I can't get that reading to my other working G4 either….!!!!!

BDAqua

Level 10

239,759 points

Oct 23, 2014 11:00 AM in response to Yiannis

That link let's me download, yet nothing downloads.

Is the other G4 an MDD also?

Is there an ADC monitor on the other one?

Yiannis Author

Level 1

99 points

Oct 23, 2014 11:41 AM in response to BDAqua

Yes its an MDD dual 1.25mhz and it has an ADC display.I was using it to turn on the other MDD also.

Its bizarre that you can't download anything……...

Could you sent me an email (p.m) to attach the file?

BDAqua

Level 10

239,759 points

Oct 23, 2014 12:00 PM in response to Yiannis

Besides your eMail being private in your profile, my eMail has a 100 KB size limit.

Yiannis Author

Level 1

99 points

Oct 23, 2014 12:03 PM in response to BDAqua

I will make it visible and use weTransfer for the file….

BDAqua

Level 10

239,759 points

Oct 23, 2014 12:03 PM in response to Yiannis

In my experience an ADC monitor may feedback/provide some voltages to the Logic board through different paths than the PSU does, allowing it to start & run fine whereas a VGA or DVI monitor wouldn't.

Yiannis Author

Level 1

99 points

Oct 23, 2014 12:12 PM in response to BDAqua

Most of the tests took place using the ADC monitor because the power button (only the switch) is not working.

I have also replaced the whole power button………..still the same results

BDAqua

Level 10

239,759 points

Oct 23, 2014 12:34 PM in response to Yiannis

I'm fairly certain we have a PSU problem, possibly combined with a logic board problem.

You can convert an ATX PSU for use on a G4...

http:http://atxg4.com/mdd.html

Yiannis Author

Level 1

99 points

Oct 23, 2014 12:39 PM in response to BDAqua

Why I can not get the 12+24 pin 12V reading on both the PSUs……..do I have two faulty ones??

One G4 is working just fine…...

BDAqua

Level 10

239,759 points

Oct 23, 2014 12:56 PM in response to Yiannis

That is my presumption at the moment, just faulty some other place on one than the other in addition.

kahjot

Level 4

2,462 points

Oct 24, 2014 12:16 PM in response to Kappy

Kappy wrote:

Are you sure, given what you've described, that the "main drive" is connected to the correct cable connector? Usually, the drive ID is determined by its position on the drive cable. If I remember correctly the main drive is connected to the ribbon cable at the end of the cable while the second drive is connected to the middle connector (for a two drive cable.) Just a thought as it's been a while since I've used non-Intel machines. If this is the case then your slave drive may actually be the main drive and vice-versa.

The other alternative if this always happens on this one drive that the drive itself is failing. Is it possible to replace it as a check?

The MDD uses cable-select, so it doesn't which drive is on which connector, as long as the drives are jumpered correctly (cable-select rather than master and slave).

The Achilles heel of those machines is the power supply. Failures were common. The machine begins to have trouble powering on reliably and eventually it just won't boot. I had to replace the power supply in mine. If that's the issue, you will have to decide whether it's worth spending any money to fix it. I have no idea what power supplies go for these days. Of course, it would truly suck to get a power supply, do the pain-in-the-butt installation, and then discover that it was not the problem after all.

Yiannis Author

Level 1

99 points

Oct 26, 2014 11:08 AM in response to Yiannis

A friend of one is going to check the PSU for any problems.

My concern is regarding test voltages.

According to this

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

The 25 V and the 5V are both standby voltages.That means that the PSU ail give these two values when its connected to main but not turn on.

The next one the 12V.its not a standby voltage ,so how I will measure that when the computer is off?

As I said in my previous message I can't measure that value to my other working G4 when it is off.

BDAqua

Level 10

239,759 points

Oct 26, 2014 11:29 AM in response to Yiannis

I think the power button must be pressed...

If after the completion of step 3, pressing the power button has no effect, and the PSU fans do not move, the PSU is likely bad.

4. Connect the black lead to pin 12 of the power supply connector;

connect the red lead to pin 24.

The volt meter should measure approximately +12V.

If you do not get a reading of +12V, recheck connections and measure again. If voltage is still not present, replace the PSU.

Power Mac G4 MDD strange startup problem