Mac G4 Digital Audio Model. Unit is, suddenly, completely dead. Is a good backup battery (1/2AA 3v), needed for a power start? Is there a separate fuse anywhere in the unit, i.e. within the Power Supply (API 9841)?

Are the contacts for the battery on the laptop good, no corrosion or anything?

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hi,

How old is the PRAM battery? If you have never changed it since you bought the computer, be aware that they last from three to five years. A dead battery will prevent the computer from starting.

And if the battery is new then follow steps below and ur problem will be solved..

Reset PMU (Power Manager Unit).

1. Disconnect all cables except the power cord.
2. Touch any metal surface to ground yourself, disconnect the power cord, and open the computer.
3. Find the PMU reset button and push it. once only. It's a tiny, tiny button, probably unlabeled, located on the motherboard and probably near the battery.
4. Close the computer, reconnect everything, and give it a try.

If this doesn't work, replace the battery. BTW, if you have a power strip, that doesn't necessarily mean that it gives surge protection. Get a good surge protector/battery backup.

Goodluck,
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Normally if this UPS is in working condition and the batteries are also good, you should be able to start the UPS by just using the battery cabinet. As soon as power is applied the fan must run and the 4 yellow led for battery/load should lit up. If it is completely dead, then a qualified technician will have to check the internal circuit. It has one main board on which all power components are mounted and a separate control board. Generally there is a 80/100 A than goes opened. I hope you can give us more information if the UPS is completely dead or the led comes up

If there's no chime, your problem could be anything from a dead battery or bad AC adapter to a dead logic board.
Does the tip of the adapter on your AC connector light up? If not, that's a problem.
When you push the button on the battery, do you get at least two glowing LCDs? If not, that's a problem.
Otherwise, try the following: remove the battery and the AC jack to make sure the machine is off. Now insert the AC jack, and reset the power management unit by pressing the following multi-key combination:
Shift Control Option Power-button
Wait five seconds, then press the power button to attempt to start the computer normally.
The instructions above are for the 1.5GHz PowerBook G4; the instructions MAY be different if that is not your model.

OSX has become unreliable.
You could spend hours troubleshooting, or simply backup and re-install from disks, takes about 40 mins

The backup battery connects directly to the logic board. From the symptoms you are describing (rather clearly, thank you), it seems apparent that your logic board may be faulty.
There are two more things you can try.
1) Reset Open Firmware: Unplug-replug your backup battery, then boot the system holding down Control-Option-O-F. Your machine will boot into Open Firmware. Type the following commands, pressing the "return" key at the end of each one:
reset-nvram
set-defaults
reset all
Your machine should restart at this point. If it starts successfully, you should be done. Otherwise,
2) Reset the Power Manager. Turn the machine all the way off (no power). Simultaneously press Shift-Control-Option-power button, then release. (Do not press the fn (Function) key during this sequence.) Wait five seconds, then press the power button. If it starts successfully, you should be done. Otherwise, you will need to see a man about a logic board, which is probably not a cost-effective repair on a 1GHz G4.

If the indicator light is dead, then yes, but check with a local mac genius at an apple store if possible...

THROW IT AWAY.  I HAVE THE SAME PROBLEM AND PANASONIC AFTER SALES "SERVICE" PEOPLE  HAVE BEEN COMPLETELY USELESS!

Many times if the battery on the motherboard dies, the computer won't startup at all. Try replacing the battery and push the tiny reset button on the motherboard and see if it will power on then.

suggest you do a clean reinstall from disk but remember to backup your data