G4 Quicksilver 733Mhz dead

Hi, I have a G4 quicksilver which when I press the power button lights up the white led but nothing happens. No fans turn, no red led inside. Have tried replacing the internal battery but still the same. Can anybody help please?

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Thanks,

- Nick

p.s. Regarding your question...it could be a dead power supply.

re power supply check

I checked the power supply voltages by bypassing the power standby(green wire in psu) and all the voltages are present. Also when that is done on the logic main board, the red led then lights but nothing. Also checked some voltages on the cpu transistors and supply is going there,and fans switch on, only when I bypass the green wire on the power supply to ground, but still no chime like it is dead.

All I wish to know is whether to order a CPU or logic main board since I do not have any parts I can try with and do not want to buy the two of them.

Thanks and any help would be appreciated.

Faulty RAM maybe?

Based upon you powering on the PSU by shorting the green wire to ground proving it is good, another option is power switch/PCB failure. Some used to fail regularly, a white plastic label on an IC used to shrivel up from heat on some PM G4's, can't remember if it was the QS or earlier models. Disconnect the power switch, then use the on switch on an older USB keyboard and see if it powers on.

If not the logic board failed is a strong possibility.

About the ram, no the ram stick is surely good because I removed it from another Imac G4 (Ishade) and it works perfectly plus it would beep I presume.

Regarding the power switch pcb, yes there is a possibility that it is faulty, but there again When I short that green contact on the power supply, should'nt I be able to hear the tone. Unfortunately I do not have an old usb keyboard with the power button.

As I said, when I short the green wire in the power supply I can get voltages on the cpu.

Is there a way to check if it is the front panel pcb by maybe eliminating it temporarily?
I will remove the front pcb and check to see if there are any signs unless there is somebody who can guide me into checking some voltages on that board.

The wierd thing is the red led on the logic board lights when I jump that green wire.

Update

Removed small panel board, no sticker found on it caked but it could be faulty.
Measured all voltages. They are all slightly higher than supposed to be like the 3.3v being 3.5v, 12v being 12.6v, -12v being -12.4v, 5v being 5.2v,
except the 28v being low at 25.8v.

Also first the fan in front of the cpu starts at full speed and then slows down. No display on monitor, no startup tone, nothing but the red led on and the fans.

I'm starting to think it might be the logic main board. do not know if I can test any further. If there is please let me know.

Many thanks

freccia said:

Regarding the power switch pcb, yes there is a possibility that it is faulty, but there again When I short that green contact on the power supply, should'nt I be able to hear the tone. Unfortunately I do not have an old usb keyboard with the power button.

Click to expand...

You are right, I missed that.

As you say, it is looking like a logic board issue.

Thanks techiesteve for your support. I appreciate your help. Will try to order one from ebay hopefully, it's either the logic main board or the cpu anyway but more likely to be the board.

Happy New Year and will see how it goes eventally.

Don't overlook replacing the PRAM battery before lashing out on more expensive hardware.

Replaced the PRAM battery, but all for nothing. Maybe I am not resetting the PRAM properly. Let me explain what I did maybe I am doing something wrong.
Waited overnight without battery.
Pressed the pram switch 15 seconds without battery and power continuously.
Placed the battery back on the board.
Measured the battery voltage which was 3.27volts
Put the power cord back on.
Pressed the power button. The light on it illuminates for the amount I press the button then it fades off.
No red led no fans nothing.

Hope I am not doing anything wrong. If I am doing anything wrong or I have skipped a step or something, please do correct me before I go out for a main board.

Thanks guys.

Pull out the video card and reseat it. Unplug the hard drive and try to start it up.

Reseat ram, reseat IDE cables, Blow it out with an air compresser or a leaf blower, check for loose cables, then test. Make sure you check the caps also

Will it beep or do something without the video card? Because maybe my video card is faulty. I need to try that one out.
I have reseated the ram many times, removed IDE connector of cd and hard disk, tried without ram as well.
I have removed the motherboard from its place to check for any signs of burnt components but nothing, no components seem to be burnt at least visually and no overheating of any component.
About the capacitors, I have looked at them, there are no real signs of leaking capacitors, but i can see like a hairline on some of the metal capacitors especially close to the cpu board. None are shorted but you cannot know if they leaky unless you replace a couple, which I might consider.
I have repaired other pc motherboards before but you could visually see the capacitors bulging (inflated). They seem to use good quality capacitors on these motherboards though.
Maybe someone can enlighten me if it is worth replacing the capacitors if you think it could be from those, I might have a go at them.
Thanks guys for your support and help, really appreciate it.

A bad video card will keep this model from starting up. Reseat the video card. Keep one stick of memory and disconnect the HD...then crank it up. Theres led's on the board that should lite up next to the CPU.

I have tried with or without the video card, the red led still would not come on.
Also tried with another video card but still nothing.
The only time the red led lights is when I bypass the green wire on the power supply and the supplies then switch on but still the front panel would not keep lit and no tone from speaker.
Do you think I can test the video card on a pc instead just to try it out?
Thanks

Update.
Tested mac with another video card but still nothing and I it works on another pc.
I think I should hear a beep if no video card is present. If no ram is present it should beep as well.

The motherboard may be dead. Especially with trying a new video card and removing the ram, and still having no improvement.

Yes I am thinking it may be partially dead, not sure about the processor though. The thing that it does not start on its own with just the power button already shows me that something is wrong with the board. Are there any tests I can do to check the processor is ok because if both are dead, it is surely not worth repairing?

You most likely have a dead motherboard. Or it could be a power supply issue, you never know. I assume if you are confident in replacing capacitors, you can use a multi meter.

Try this:

How To Manually Test a Power Supply With a Multimeter


Hope this helps! -Air