Mac Forum / General / Hardware / February 2006

Try here
http://www.whoopis.com/computer_repair/

They have service manuals for most macs to dl.

HTH

Dave

Knowing the G4 model will help make suggestions.

At least try:

(ground yourself before mucking about inside the case by touching the
metal power supply with unit still plugged in).

Check all motherboard connections (unplug & plug in again all cables)
RAM
PCI cards
Hard drive cables

Check the battery & replace if necessary (should read 3.6 volts)
(battery available online OWC about $5, or Radio Shack about $10)
Reset PMU (CUDA on older models) a button near the battery
Press the PMU ONCE (too many presses leaves it in corrupt state and can
prematurely drain even a new battery in day or two instead of 4--5
years).
==========
You can indeed have hardware problems but the above may fix it without
additional expensive costs.

No video is often a PMU (power management unit = controls many boot time
startup features) problem. Some macs won't display video or even start
with a bad PRAM battery. PRAM battery generally good for 3-5 years.

Good luck.

Morenuf

Were their any symptoms or catalysts (like electrical storms) before
the problem?

We've seen this primarily due to a week power supply, corrupt PMU
(which a reset fixes), bad RAM, bad PCI card or bad CPU card.

First try a motherboard reset. There is a small button on earlier
PowerMac G4s in the right rear. it is normally by the small motherboard
battery. Once pressed, it should reboot.

You can also do a hard reset by removing the motherboard battery for a
few minutes and hitting the rest button. On most systems, the reset
(CUDA on early models, PMU on later) button is found next to the
motherboard battery.

Although a dead MB battery will create the symptom, on G4's you can
remove and hit the reset to restart. The battery itself shold read
3.6xx volts.Unlike the MB battery in a PowerBook, it is not
rechargeable.

Gary Dailey
http://daystar-tech.com