PowerMac G4 MDD Random Power Shut Down (power fail?!?) - Page 1
Forum section: electronics / general

author: DiTBho
author_rank: Super Contributor
timestamp: February 17, 2023, 08:27:11 am
content: It may sound weird because it's a very old machine (mid 2000s), but I am massively using my PowerMacG4 MDD2xPPC7455@1.2GHz2GB ram, 4x512MB1x200GB pATA HDDVideoCard, ATI-Rage-128-PRO AGP-4xSCSI, Adaptec-2930 (attached to a A4 scanner)to develop crazy PPC-things with the Altivec Co-op on GNU/Linux.The computer has been working fine for years, since a couple of days it makes weird shut-down at random times and during various types of operations, like when I am compiling massive amount of code. CPU and hard drive temperatures were well within range, the installed battery tested at 2.8 volts (pretty dead, I think), indeed the RTC clock always fails, but I don't care too much becauserdate -s time.nist.govthis tool automatically synchronizes the clock.I don't have a serial console on the machineCONSOLE=/dev/tty1because PowerMacG4 don't have an exposed connector for a lvTTL(3.3V)-RS232-PHY. There are two serial lines on the motherboard but they are wired to the Modem.I am willing to hack it, someday i will, meanwhile I am remotely connected from a Laptop through ssh, and the MDD stays hidden upstairs with a CRT and a Keyboard connected as "local console" that nobody uses and watches.When the computer is powered off, the PSU doesn't make any kind of spark noise, and it seems working OK, as well as the two cooling fan ventilators inside the chassis.I have already replaced the power cord, but this doesn't alleviate the conditionWould you consider the PSU to be the most likely suspect?In case what? Replacing old capacitors with fresh ones?mumble ...idea, suggestions are welcome

author: xmris
author_rank: Contributor
timestamp: February 17, 2023, 08:42:24 am
content: nice machine you have thereI think you can get RS232 via a serial USB just be aware not all of those dongles are wotking with OSX(I had a QuickSilver some years ago) , Belkin's and ones with the PL2303 (the original not fakes) are working as I remember.You are right about the PSU, check its caps - it is possible to re-wire an ATX for power macs - guides on the net- also clean the contacts of the DIMMs

author: DiTBho
author_rank: Super Contributor
timestamp: February 17, 2023, 08:56:03 am
content: Quote from: xmris on February 17, 2023, 08:42:24 amLinux/PPC32-beCode:10 Mbyte /boot/kernel-2.6.39-1xG4 # smp disabled11 Mbyte /boot/kernel-2.6.39-2xG414 Mbyte /boot/kernel-4.16.0-1xG4 # smp disabled15 Mbyte /boot/kernel-4.16.0-2xG415 Mbyte /boot/kernel-5.1.17-2xG4 # <----- currently in useI could try to buy & plug a PCI_RS232 card. Better than USB, I think.( I don't have a USB-to-RS232, anyway, I will buy both )Quote from: xmris on February 17, 2023, 08:42:24 amOK, thanks!

author: DiTBho
author_rank: Super Contributor
timestamp: February 18, 2023, 02:51:04 pm
content: This morning I measured again the battery: it's dead!The voltmeter measured ~0.5V.A brand new battery should be 3.6V.I reinstalled the battery, now the machine does't power on at all.i think I have to replace itBut could that be *the* problem?

author: ferdieCX
author_rank: Regular Contributor
timestamp: February 18, 2023, 03:06:17 pm
content: Replace the battery. A depleted one can produce all kind of problems.Nice machine, I used one up to 2015.

author: DiTBho
author_rank: Super Contributor
timestamp: February 18, 2023, 10:33:10 pm
content: Brand new battery installed.It doesn't help.I removed all the PCI cards, cleaned the ram, reinstalled only 1 bank of ram.It doesn't help.I removed both the hard-drives.Now the machine boots from the CDROM, but it still randomly shuts down.mumble

author: themadhippy
author_rank: Super Contributor
timestamp: February 18, 2023, 11:12:43 pm
content: maybe worth removing any heatsinks,given them a good clean out and some new thermall paste,same if theres any fans in there

author: BrianHG
author_rank: Super Contributor
timestamp: February 18, 2023, 11:14:23 pm
content: You need a new power supply.The filter caps are probably dying and an ever current or over voltage emergency shut down is taking place.Same happened to my PC awhile back.However, this cap problem might also be on your motherboard, like slow dying tantalums or electrolytics. (These can short the supply rails causing the power supply to emergency shutdown...)

author: DiTBho
author_rank: Super Contributor
timestamp: February 19, 2023, 12:10:37 am
content: It's going too bad now.The hardware is unreliable and corrupts my file-system.I tried with a different PSU, kindly lent by a friend.It didn't help. It shuts down in 20 seconds. Even with HDDs disconnected.I then removed the heatsink, cleaned everything, added fresh thermal paste.It didn't help.So, it must be something on the motherboard.And in this case, I have to accept it: give up.R.I.P.I need areliablePPC32/be machine with PCI32bit slots to develop stuff.(otherwise a MacMini/PPC would be perfect)So, I'd better buy a new second hand PowerMac-G4 MDD.I can recycle PCI cards and ram from this machine to save money for the new one.

author: andy2000
author_rank: Frequent Contributor
timestamp: February 21, 2023, 03:32:51 pm
content: Pretty much all of the power supplies for these are bad by now. They run hot, and have a lot of cheap capacitors that were already failing 15 years ago. Unless your borrowed power supply has been rebuilt, it's likely also bad.Random shut downs, instability, and going completely dead are all common symptoms of a bad power supply. The motherboard and CPU are very reliable.The battery isn't required for this system to work properly. Wen you install a new battery, do it with the AC power plugged in, and hit the PMU reset button as soon as you install the battery. I find that these computers can get in a state where it draws a large amount of current from the battery if you're not careful.

author: DiTBho
author_rank: Super Contributor
timestamp: February 21, 2023, 04:19:33 pm
content: Quote from: andy2000 on February 21, 2023, 03:32:51 pmwhat about aApple PowerMac G4 MDD ATX Power Supply Adapter Cable?If it's reasonable, I could try to use a modern PC-PSU (500Watt)

author: BrianHG
author_rank: Super Contributor
timestamp: February 21, 2023, 06:50:06 pm
content: Careful, I see tantalum and smd can electrolytic caps on that motherboard....Without a thermal camera for analysis, just tying a good modern 500+ watt supply might cause a nasty tiny explosion somewhere.

author: andy2000
author_rank: Frequent Contributor
timestamp: February 22, 2023, 06:58:11 am
content: Replacing it with a modern PC power supply using an adapter is a valid option. It won't need a very high power rating compared to a modern computer. There's no great risk since any half decent power supply will shut down in the event of a short on the motherboard.

author: DiTBho
author_rank: Super Contributor
timestamp: February 22, 2023, 09:48:33 am
content: Thanks guys, my mood is not the best these days, I really need a PPC32 machine.My CPU and RAM module all work on my friend's motherboard, while my motherboard *sounds* dead because, when I tried with a borrowed PSU, P-battery and my friend's RAM (all known to work), did not play the "Apple dong" sound, which means ... damaged or dead.Who knowsI ordered a second-hand motherboard, and I will try to adapt an ATX PSU