On my machine, at least, this is called the "CUDA switch. Reportedly, pushing it more than one in a power cycle will render your computer useless! From what I've read, it's a problem with the logic board or the power switch board, and would have been replaced under warranty had the problem shown up soon enough. If that doesn't fix it, it may be a problem with the front panel circuit board.
Yes, I had this same thing happen on my mirrored door G4. And I found the same solution.
All I did was put a new battery in. Thanks for posting this. I think there was something on the Apple website about it recently - something to do with the battery draining because of some power surge or improper shutdown I have rescued dozens of G4's with this symptom by simply unplugging the power cord, removing the battery, counting to 10, reinserting the battery and power cord - and booting.
Power Mac G4
It's a good idea to always check the voltage on the battery because of the discharge curve on Lithium ion batteries. The drop off is rather steep as compared to a alkaline type which drops off gradually. Since the motherboard doesn't draw that much power, simply warming it up will often do the trick ie. I hope you don't mean warming up the battery.
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You don't want to warm up a lithium ion battery. Just google what could happen if you do that.
Actually, you want to measure the battery's voltage and its current--lithium batteries at least the 3. What's happened is the battery's chemicals have changed state, to the point where the battery is basically a big resistor and so they can't deliver enough current, though the voltage deceptively still looks OK. Unfortunately, many cheap digital meters don't have a current measuring scale. Now you tell me! I junked the machine! My symptoms were exactly what you described!
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The geniuses really aren't. This was a simple PMU issue. There's no reason to waste your time with pulling the battery out. Just push the button on the logic board. ACSA There probably was a logic board issue after all. I found it hard to believe myself, but it's what happened. I subsequently managed to retrieve the machine and reset the PMU - now it works fine.
There was nothing wrong with the logic board. Resetting the Power Manager for a none starting Mac is a standard procedure and is fully documented on apple knowledgebase. I not sure why it appears as a hint on this in When Mac users have been using the technique for years. What is important to know is that you must neve reset the PMU button twice in a row. You must leave at least 10 to 15 seconds if you think you need to press it again.
Power mac g4 m8493 manually
If you do press the button twice you can crash the PMU which would cause the batttery which normally last for years to expire in 3 days. As well as keep your machine from ever booting again without replacing the logic board They are: 1. Unlpug the power cord. Using a non-metalic tool your finger, if it'll reach push the PMU reset button location varies by machine ONCE and for no more than one second.
Wait seconds. Plug the power cord back in and hit the power button. Note that a bad logic board, processor or stick of RAM can cause the same symptoms described by the original poster so a PMU reset is no guarantee.
I don't know where the myth came from that suggests if you crash your PMU you need to replace your logic board but it's not true. The most you can do crashing PMU is to expire the battery. For those that want the official procedure for resetting the PMU here it is. The PMU is a computer within a computer.
Important: Be very careful when handling the logic board. If the PMU crashes and is not reset, the battery life goes from about five years to about two days.
Many system problems can be resolved by resetting the PMU chip. When you have a computer that fails to power up, follow this procedure before replacing any modules: 1. Disconnect the power cord and check the battery in the battery holder. The battery should read 3. If the battery is bad, replace it, wait ten seconds, and then proceed to step 2.
If the battery is good, go directly to step 2. Press the PMU reset button once and then proceed to step 3. Wait ten seconds before connecting the power cord and powering on the computer. If the computer does not power on, there is something else wrong with it; refer to the "System" section of "Symptom Charts" in this chapter.
After resetting the PMU, be sure to reset the time, date, and other system parameter settings. I have had a number of clients with un-revivable logic boards who've told me that before bringing their machines in for service, someone they knew told them to either hit the PMU reset button several times in a row or even to hold it down for thirty seconds or more.
Granted, this is just a correlation and not a proven cause and effect - more likely these folks may have just had an ESD incident while they were dinking around inside their machines or the MLBs had already failed in some other way - but why take chances?
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BTW, thanks for posting the official procedure. It's reset by simply unplugging the power cord for 15 seconds. I would hazard a guess that Apple may be tired of all the warranty logic board replacements that they've done because the user did an improper PMU reset A workaround is to get a small piece of paper something which is a bit stiffer than normal paper works best like a matchbook, index card, etc. This effectively disconnects the battery.
Wait a good minutes, then remove the paper, and start up. This is a copy of an email I sent in response to a mailing-list posting about a system that sometimes spontaneously re-boots after being shut down and sometimes won't boot when the power button is pressed it was a MDD PowerMac.
My edited response to the poster was: Your problems might be related to the following: It turns out that some of the ATI Radeon graphics cards e.
Power Mac G4 - Part 3 : Upgrades!
I've found that using some VGA cables i. Anyway, I hope this helps someone I bought a used G4 Quicksilver at auction. It looks in great shape, no damage, cracks or signs of misuse.
Anyway I have no luck in getting it to power up. The Front panel light will not stay lit, but the fan is running and the little red light on the mother board is lit.
Power Mac G4 Quicksilver Repair
I replaced the battery and used the info you guys posted about the power button located on the board also, but still no luck. Any other suggestions? I have to to the same thing to power up my cube, the only problem is that it only works once. After turning the power off I have to redo the hole procedure to start it up again.
The following check list is from the cube engineers manual. As you can see everything points towords replacing your logic board if yoru rule out issues with the power supply, dc-dc Board etc.
Apple POWER MAC G4 Service Manual
If have resetting your PMU your still getting issues and you've followed the procedure here, then I would use the hard ware test cd that came with your cube which will test your logic board. No apparent power no sound and power LED is not lit 1. Verify the power outlet is good. Replace the power cord. Reset the logic board. Check for trickle voltage on the power adapter connector.
Refer to "Power Adapter Verification" in this chapter.
If verification fails, replace the power adapter. Disconnect external devices, including the monitor, and start up the computer. Remove internal cards and start up the computer. Disconnect internal hard drives from the logic board and start up the computer.
Reseat the DC-to-DC board in its connector. Check the modem connector. If the connector has any bent pins, replace the logic board. Replace the logic board.
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