PowerMac G4 (Quicksilver) Power Supply

Have you taken the power supply out and cleaned it out? I actually use a leaf blower to do this (homemade) and have recovered many power supplies like this. In lieu of that check on ebay they can be had very cheaply when compared to OEM. There's a new one there right now starting at $.99. Check the part # and see if it's compatable with your machine. Richard

Also you could check out:

but be aware that the capacitors in switchmode supplies can be very dangerous (as noted in Sam's site). Some SMPSs won't operate properly unless they're under load, as here in the pdf. (below): "Note: To verify the power supply, you need a volt meter. When connecting the volt meter leads to specific pins, make sure the power supply remains securely plugged into its connector on the logic board." I also have the pdf. take apart, troubleshooting and pinouts for the mirrored door G4. Might be similar. Richard

Something worth checking out are the fans. I'm not sure if the Mac does this, but many PC motherboards will shut down immediately if they detect the CPU cooling fan is not running and will exhibit this exact same behavior. They normally use 3 wire fans and monitor the tachometer line.

Wow! A huge thanks to all of you so far! I didn't expect this many replies. Here are some more details about it. I had checked it out to see if it was dirty, and it looked pretty clean (also no charred components when I glanced around inside). I can try cleaning it out again. All the fans spool up for a few seconds before it just stops dead in its tracks. The Apple P/N: 614-0157. It appears that there are no matches for this machine out there at the moment (DigAudio, MDD, Sawtooth are all different!). Also, the fans are all two wire as well, but if they are all working anyway I wouldn't suspect that to be the issue. Another issue is that I have been told it is remotely possible that the logic board is the problem instead. That is much more expensive, and still difficult to tell which is causing this strange problem.

-Chris

"James Sweet" wrote in message news:AeRAf.1957$zh2.1452@trnddc01...

Chris wrote:

You could try resetting the PMU, This is from the mirrored door take apart.: "Resetting the PMU on the Logic Board The PMU (Power Management Unit) is a microcontroller chip that controls all power functions for this computer. The PMU is a computer within a computer. Its function is to: =B7 tell the computer to turn on, turn off, sleep, wake, idle, etc. =B7 manage system resets from various commands. =B7 maintain parameter RAM (PRAM). =B7 manage the real-time clock. Important: Be very careful when handling the logic board. The PMU is very sensitive and touching the circuitry on the logic board can cause the PMU to crash. If the PMU crashes and is not reset, the battery life goes from about five years to about two days. Note: For the location of the PMU reset button, see "Logic Board Diagram" in the Views chapter. 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 3.3 to 3.7 volts. If the battery is bad, replace it, wait ten seconds, and then proceed to step

2=2E If the battery is good, go directly to step 2. 2. Press the PMU reset button once and then proceed to step 3. Do not press the PMU reset button a second time because it could crash the PMU chip. 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. Note: The above procedure resets the computer's PRAM. After resetting the PMU, be sure to reset the time, date, and other system parameter settings." Also here's the power supply verification procedure: "Power Supply Verification To power on, the computer's logic board requires a "trickle" power of +5V. If the system fails to power on, first reset the PMU. Then follow the procedure outlined below to determine whether the problem is related to the power supply. Note: To verify the power supply, you need a volt meter. When connecting the volt meter leads to specific pins, make sure the power supply remains securely plugged into its connector on the logic board. The following figure shows the pins and voltage on the computer's power supply connector. (The color noted represents the color of the wire attached to the pin.) 1. Plug a known-good power cord into the computer. Do not turn on the computer. 2. Connect the black lead of the volt meter to pin 12 of the power supply connector; connect the red lead of the volt meter to pin 14. The volt meter should measure approximately +25V. If you do not get a reading of +25V, recheck the volt meter connections and measure the voltage again. If voltage is still not present, replace the power supply. If you do measure +25V on pin 14, the power supply is likely OK. Go to the next step for further verification. 3. Check the trickle voltage by connecting the black lead of the volt meter to pin 12 of the power supply connector; connect the red lead of the volt meter to pin 1. The volt meter should measure approximately +5V. If you do not get a reading of +5V, recheck the volt meter connections and measure the voltage again. If voltage is still not present, replace the power supply. If you do measure +5V on pin 1, the power supply is likely OK. Go to the next step for further verification. 4. Start up the computer by pressing the power button on the front panel. If the computer starts up normally, the power supply is OK. If the computer does not start up normally, go to the next step. 5. Check to see if the power supply fan is spinning. If the fan is not spinning, replace the power supply. If the fan is spinning, go to the next step. 6. Connect the black lead of the volt meter to pin 12 of the power supply connector; connect the red lead of the volt meter to pin 24. The volt meter should measure approximately +12V. If you do not get a reading of +12V, recheck the volt meter connections and measure the voltage again. If voltage is still not present, replace the power supply. If you do measure +12V on pin 24, the power supply is likely OK. Go to the next step for further verification. 7. Connect the black lead of the volt meter to pin 12 of the power supply connector; connect the red lead to pin 6. The volt meter should measure approximately +3.3V. If you do not get a reading of +3.3V, recheck the volt meter connections and measure the voltage again. If voltage is still not present, replace the power supply. If you do measure +3.3V on pin 6, the power supply is likely OK. Go to the next step for further verification. 8. Connect the black lead of the volt meter to pin 12 of the power supply connector; connect the red lead to pin 3. The volt meter should measure approximately +5V. If you do not get a reading of +5V, recheck the volt meter connections and measure the voltage again. If voltage is still not present, replace the power supply. If you do measure +5V on pin 3, the power supply is likely OK. Go to the next step for further verification. 9. Connect the black lead of the volt meter to pin 12 of the power supply connector; connect the red lead to pin 10. The volt meter should measure approximately +12V. If you do not get a reading of +12V, recheck the volt meter connections and measure the voltage again. If voltage is still not present, replace the power supply. If you do measure +12V on pin 10, the power supply is OK and the testing is complete. You have verified that the power supply is not the cause of the "no apparent power" symptom. pinouts: Pin 23 GND Black Pin 22

Hmm didn't take the pinouts. Pin 24 +12V YellowBlack, Pin 23 GND Black, Pin 22

Howdy!

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Also,

I just had a machine come into the shop with the exact same symptoms.

Try pressing the CUDA button for about 10 seconds with the power unplugged, then see if it comes back up.

RwP

I had a Blue G3 machine which had a blown supply the form factor was identical to an ATX. It had a blown main power FET which had a rating IIRC of 700 Volts 10 Amps. I replaced with one that was 600 Volts 5 Amps and it ran. The only other thing to bear in mind is that the wiring is the same as an ATX however one of the supply voltages wasn't necessary , maybe -5V or -12V.

This site had quite a bit of info

Andrew