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My G4 is 'dead' - possibly PRAM prob

I bought a used G4 and it worked OK for a bit but it used to lose the time and date.

One day, it wouldn't start at all, so I worked out it was probably a PRAM problem and changed the internal battery.

The new battery measures OK on my (admittedly very basic) meter but nothing happens when I try to power up the machine.

I have checked and there is mains voltage going to the power supply. Any ideas?

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Reply to: My G4 is 'dead' - possibly PRAM prob
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No start up

Here is a trick I have used for many years.
Remove the battery from the machine.
Remove the power plug from the machine.
Press the CUDA button(it is on the motherboard), little square thing with a top that looks like a pencil eraser. ONCE
Press the Power On button on the front of the machine.
Leave the whole thing for at least 30 minutes.
Put the battery back in
Put the power cord back in
Press the Power On button on the front of the machine
Sit back and enjoy the startup chime.

If this works, let me know and I'll tell yo what we just did. If not, tell me and we'll start again


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Didn't work for me

Thank you so much for the advice.

I followed it carefully but I'm afraid it didn't work for me. The machine still shows no sign of life.

I appreciate your input,

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G4 No start

Well that rules out a PRAM problem then. What we did there was to totally reset the logic board (Motherboard) Removing the battery and the power cord removed all sources of power. Pushing the "ON" button discharged the capacitor the kickstarts the power supply. By leaving it for 30 mins, all vestiges of power were drained from the machine. 99 out of 100, this works and the machine bursts back into life. Sorry for you being #100. If nothing happened at all, I would suspect, first, the Power Supply. There are ways to test this ATX type power supply but the normal step is to replace it and see if that was the problem. Unfortunately, this is an Apple part so a regular ATX power supply is not going to fit.
Are you absolutely sure that there are no lights at all on the logic board after you push the on button? It's quite safe to have the door down when you are doing this. Just watch the cat and the coffee!
This may sound redundant, but, make sure that all the connectors to the logic board are seated well. Disconnect them and put them back. Power cord out for this step.
Remove any extra RAM that you have installed, ditto any extra hardware. The only thing plugged in should be the keyboard, mouse, monitor and power cord. Try to power up. If you have a friend with a working G4, beg, borrow or steal their power supply. Purely for diagnostics, you understand.

Good Luck


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Can I repeat procedure?

Thank you again for the input. Knowing what the procedure is doing is extremely helpful, as is advice on what else I can try. I do have access to an almost identical G4, so swapping the power supplies would be possible.

Before I do that, I'm wondering if I'm simply not following your instructions correctly. When I opened up the G4 again, there was a little red LED glowing, which suggests the motherboard is getting at least some power.

Is it safe to repeat the procedure? (You said to push the button on the board only once.) I'm wondering if I have correctly identified the button. The thing I am looking at is above the positive connection for the battery, about 1/4 inch square metal casing with a round button about the size of an artificial sweetner. However, there was nothing about its action to suggest that it was a button when I pushed it.

Thanks again

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Repeat the Procedure

You are correct about the location of the CUDA button. If you use a blunt instrument, no pointy things, to push it down, you will feel a slight give in the button. That's all it takes. Push straight down and then release. I usually use the end of a pencil to push it with. Once is the recommended number of times as there is a theory that more than that will mess up the Firmware on the board. This is NOT from experience, however...
Yes, it is quite safe to repeat the procedure. Check the battery is in the holder correctly. I'm sure you have already done that given the observation about the positive connection.

Go at it again and good luck


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have a laptop not a desktop

do you have any suggestions? my laptop is completely dead. its a G4

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Off topic

Just where, in the Green and Pleasant land, does Mr simoncroft hail from?


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I do believe you'll have good luck if you boot your mac and hold down command-option-p-r (four keys)

It will chime and reboot. After that it will boot properly, unless there's another problem. Any time the battery's involved, it's best to zap the parameter ram (PRAM).

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If you read the posts, you will find that removing the battery and resetting the logic board does exactly that.


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