But no power thru usb ports or video monitor; reset pmu switch; replaced battery; red light on mother board remains on; fan speeds up and slows down heat coming off prossesor; if i hold down power button for 5 to 10 sec power shuts off hit power button again power comes on but light goes off tried all combonations on key board to trigger a restart but i dont think the key board is registering no lights come on the key board ;unplug the monitor from the computer and it says cable unpluged plug it back in and and the monitor goes back to sleep ....//////please help??????
My mac G5's screen goes dark when i'm on the web and the fan sounds like it is trying to turn on but stops as the screen goes dark. When I click and pick up the mouse to get the screen back on I notice the mouse light is off, than it flashes on as does the screen......this happens frequently. its it the mouse, light board or power board?? help
You need to replace the power supply. The fan sound is the fan for the power supply and not the computer. for cheap parts or used goto headgap's. They know what you need and probably even help you replace it yourself.
Power-on LED illuminates when power button is pressed, fans spin, and boot tone chimes, but there is no video
1. Reseat video card. (Make sure video card is fully inserted in connector and end of card is secured by the connector latch.)
2. Reset PRAM (restart computer while holding down Command-Option-P-R keys until second boot tone chimes)
3. Replace video card
4. Reset logic board. Refer to "Resetting the PMU on the Logic Board" in this chapter.
5. Replace logic board
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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:
tell the computer to turn on, turn off, sleep, wake, idle, etc.
manage system resets from various commands.
maintain parameter RAM (PRAM).
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.
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. 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 "Startup Failures" 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.
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now this is with a desktop not a laptop right?
and the key combo for a reset is Command + Option + Power Button. Thats the equiv.. to a Ctrl + Alt + Del on a windows system.
But does you mac turn on and load to the desktop? or does it just start up and hum, and nothing on screen and all peripherals don't respond as well?
If that is what you are getting then the power supply needs to be replaced. I've had that same issue once with my PowerMac G4 Dual Proc.
(ya i know you can start up and the fan hums and all but thats the fan for the power supply not the fan for the board. if you have a older mac the cost for a new power-supply shouldn't be that much. And you can probably order it and replace it yourself.
a good cheap place i've found so far is here:
http://stn2.headgap.com/resale/FMPro?-db...
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