PowerMac G4 not powering on after MOBO reflowing

[viksn0w]

My PowerMac G4 still gave that strange error: Bus Error, I searched online and asked to some friends and everyone just said "try to bake the mobo", so I tried to bake my mobo at 170°C - 340°F for 10 minutes, now I just finished the assembling part, and nothing... now it doesn't power on, the only thing that's powering on is the button, some thoughts?

EDIT 1
I just noticed that the electricity is actually passing trough the motherboard considering that the Power Button LED is attached to the motherboard and is powering on

EDIT 2
I searched online and it could probably be the PMU Battery that is probably dead, considering that it's the original one and it's wasn't changed since 2001. The battery officially dies when it's removed from the MOBO or the power-flow in the MOBO it's interrupted for long amount of times and most importantly the dead of this battery or if the battery is totally missing the Apple Manual at page 85 says that this missing battery could cause video glitches or actually the not starting up
https://manuals.info.apple.com/MANUALS/0/MA666/en_US/0342088-EN.pdf

[GaryN]

Thought 1: Your friends are idiots.

Thought 2: You had a computer that was at least starting and trying to tell you what might be wrong. Now you've killed it completely and you want to know what to do. It sounds really stupid when I put it like that, doesn't it?

Thought 3: You haven't even said exactly what model it is - there's more than one G4, plus there's desktops, laptops etc. There are specific troubleshooting steps for specific models.

Thought 4: Whatever you do while trying to sort this out, do not hold your breath - you'll almost certainly turn blue first.

Did you bake the MOBO with the CPU still attached?
   YES: Just throw the whole thing away.
   NO: Post exactly what model this is; what video card is in there if you know; what monitor, RAM - everything. While you're waiting for a response, get a magnifying glass and examine the MOBO closely, especially looking for any large parts that may have come detached by their own weight while cooking. If none are found, carefully reassemble again, get a battery follow the troubleshooting that's been posted and report back.

[viksn0w]

1. It's not actually the first time that I tried to bake a mobo, it usually went always well, I mean this is the first time that this kind to thing happened.

2. The mobo it's not totally dead, the power is flowing trough it in fact the LED of the power button is turning on and the reset button also

3. I removed EVERYTHING that was actually removable, so CPU, batteries, video card ATI, IDE Control Card etc...; the model is a PowerMac G4 M5183 Digital Audio with 128MB of RAM

[GaryN]

1. Well, not to be a pessimist, but there's a first time for things to go wrong as well.

2. All the power button LED proves is that there's standby power from the PSU.

3. You will have to start by installing a new battery. A dead or missing one, as you read, actually CAN cause a no-start condition. Get a battery, put it in and see if any thing changes. With luck, you may get back to at least the "bus error" point.

Good luck.

[macStuff]

cant say "reflowing" is something id want to do to any motherboard of any type for any circumstance;
especially something thats so easily replaced via amazon or ebay

time is short; life is short; throw it out and buy another and move on to something more important + more rewarding

[OS923]

In the G4 the battery does not only charge the PRAM but also the PMU, a chip responsible for the ignition of the computer. Without healthy battery, it's logic that it doesn't start up.

A G3 can work without battery.

Has anyone here tried to boot a G4 without battery?

[hageir]

Uhm...
When you say Bus Error,
by any means are you referring to the error window with the bomb?
If so, you most likely were using an incorrect Install/Restore disk for the Digital Audio model (I had that experience until I used a correct CD)

[macStuff]

1. It's not actually the first time that I tried to bake a mobo, it usually went always well, I mean this is the first time that this kind to thing happened.

too bad you didnt come on here with photos/details to ask us BEFORE you chose to listen to your friends. there would have most likely been many many many things for us to suggest that would haev been alot more logical + rational rather then jumping to the (probably false) assumption that something was wrong with your hardware;

honestly... because g4s aer so cheap + ez to find;
just buy another powermac g4 + move on with life; 

[SDG]

Has anyone here tried to boot a G4 without battery?

Yup. My DA came without a PRAM in place. Never bothered replacing it. Works fine even after switching to a SATA card to boot from. The DA even has a Sonnet dual cpu upgrade for added instability.

As far as my experience goes, only the Pismo will refuse to boot with a dead PRAM battery in situ. All my other G3s and G4s work fine with or without a PRAM battery.

[FdB]

“Coloring outside the lines a bit?”

Admittedly I’m quite often prone to some rather unorthodoxed approaches to “fixing” old G4s - yet I’ve never considered baking any G4 MOBO (yet). Anyone else ever done this?

I have however baked numerous boards (more than four) out of several fairly-recently manufactured flat panel televisions resulting with 100% working success. Seems that maybe the quality of the soldering on these recent components might not be quite what it should have been… or perhaps now, planned obsolescence could have something to do with it? (At any rate, maybe this says a great deal about the original manufacturing quality of ye olde G4 machines?)

Given my success rate with the television boards… maybe a quick little “EZ bake” of a MOBO might warrant some further investigation? (May be worth a try?) Really doesn’t take all that long to strip out & down a MOBO for baking… and if it works… well, no expense & no waiting for a new MOBO to be delivered. (As long as you don’t jostle something loose after baking / cool down times afterwards, before moving is important.) *I’ve an old Quicksilver MOBO ‘round here that I replaced. When time allows, I might just try baking that old one.

If it doesn’t work… sure, replacement boards are available. But yes… I hope the new battery does take care of the current non-working state. If it does, then what did baking the board really harm?

After all, Mother IS the necessity of invention…
but yup, I might have tried running AHT and a new battery first.
Do keep us all posted.
(I may have a MOBO - if you need one. PM me.)

[OS923]

The PMU is a sensitive chip that can easily go TILT. This can result in the G4 not starting up, or even failure to turn on, what happened to my FW800 MDD.

The Power Management Unit (PMU) is a microcontroller that governs power functions of digital platforms. This microchip has many similar components to the average computer, including firmware and software, memory, a CPU, input/output functions, timers to measure intervals of time, and analog to digital converters to measure the voltages of the main battery or power source of the computer. The PMU is one of the few items to remain active even when the computer is completely shut down, powered by the backup battery.

For portable computers, the PMU is responsible for coordinating many functions, including:

• Monitoring power connections and battery charges
• Charging batteries when necessary
• Controlling power to other integrated circuits
• Shutting down unnecessary system components when they are left idle
• Controlling sleep and power functions (on and off)
• Managing the interface for built in keypad and trackpads on portable computers
• Regulating the real-time clock (RTC)

The PMU controls almost every power-consuming function in an Apple computer. It is constantly running diagnostics on the various power-related operations and checking them against the current Energy-Saver settings, allowing the PMU to actively manage power consumption for optimum user performance.

The PMUs functions may become corrupt over time. If this happens, it may become unresponsive and stop performing tasks. The user may not notice the PMUs malfunctions so much as the side effects of the corruption, including:

• Failure to turn on
• Failure to restore from sleep mode
• Failure to recognize connected devices (FireWire, USB, etc.)

Resetting the PMU in these circumstances can be a relatively quick and easy fix to some of these issues. There is a keyboard shortcut on newer Apple laptops with an internal battery, nicknamed "SCOP". This stands for Shift Control Option Power. This "reboots" the PMU software in order to get it working as it should. For Apple laptops with a removable battery, resetting the PMU involves unplugging the power adapter, disconnecting the battery, then holding down the power button for five seconds. Another PMU-related fix would be to reset the logic board, where one removes the backup battery on the board for a few minutes, then reinstalls it, causing the PMU to reset itself with clean, fresh parameters (that need to be corrected, if desired, to its previous state) during the next Mac OS boot (for typical PC users, this is similar to "resetting the CMOS").

The PMU is very sensitive and a reset may be necessary if a backup battery dies. Even plugging in one's laptop in the wrong order can cause issues (power into the outlet first, THEN power to the computer). Never turn off an attached UPS without first unplugging the AC adapter.

I find this unfortunate, because when it happens to you, your first thought is that the power supply is dead.

In my opinion, the greatest risk in blowing up your power supply is that you use an Apple monitor with an ADC connector, which can use up to 100 W.