Thank you for your interest for help.
I want to know what the problem is so that I can replace the part or give up at least.
SYMPTOMS are :
1. No green light on the front panel board (near the power switch)
2. No "Bong" sound
3. Red steady light on the motherboard
4. Power fan, cpu cooling fan, and vga fan all rotates.
5. DVD drive door doesn't open if the cable is attached to the motherboard.
However it DOES open if the cable is disconnected.
6. Hard drive doesn't rotate if the cable is attached to the motherboard.
However it DOES spin up if the cable is disconnected.
WHAT I DID RIGHT BEFORE HAVING THIS HEADACHE :
1. I pulled out MODEM daughter card and gave it to my friend who needs modem.
I asked him to give me back just to test whether that's causing problem or not but
it turned out it's not.
2. I don't know why I did it but I was very curious about macintosh CPU so I removed the
CPU board and enjoyed(?) looking the CPU... it was smaller than I expected
THINGS I TRIED SO FAR :
1. After doing extensive google search, I figured out in most case pressing PMU button fixed the problem. I also read a warning not to press it in a row. I tried more than hundered time so far no hope.
2. Measured the voltage of on board battery. It's 3.9 Volt. Just in case I bought a new one. Still it's holding good charge.
3. Tried to replace a ram also. Pulled one stick from working powermac g4 so I'm sure ram is okay.
4. VGA card is tested also. No problem.
My guess is either main board is gone or cpu board is gone. I want to know exactly which parts is causing a problem. Any idea ?
I am not sure if it's a ZIF type pin setup, but check to make sure there is no dust on it. If it's a connector that has kinda of meld between male/female connnectors (kinda like just a "plug") check to make sure there is no dust.
You might want to check and re-seat the CPU. It might be that it is not plugged in right. that's my best guess. and please tell me your grounded yourself before tinkering with the system?
Grounding is the first step when working on a computer. It prevents component failure from static buildup. Remember, you don't have to SEE the spark for it to be deadly. It just has to be present.
**EDITED FOR WORD CHOICE
Thank you for your fast reply!
Frankly I don't understand what you mean by "ZIP type pin setup".
I cleaned up by air gun so I guess what ever that part is there should be no dust right now.
I re-seated the CPU. Doesn't work.
With no memory, still fan is working and there is steady red light on the board. No beep or sound. strange...
It sounds very similar to the problems I'm having with a Quicksilver which I just recently described here:
My problem points directly at the power supply unit. Unfortunately, the only way to know is if you can measure the voltage coming out of the PSU, or if you can try another PSU, but G4 tower PSU's are still very expensive, and the only way you can rig up a cheap ATX PSU to work in the Digital Audio is if you can also find a 24 or 28volt external power adapter to run one of the pins in the power connector.
It's a nasty business, because it could be my motherboard and CPU as well as the PSU, so I may end up having to replace the major components. I hope your problem is a lot simpler.
This makes me wonder if the G4 towers' PSU's have a congenital problem equivalent to the PAV congenital problem of the slot loading iMacs. That 28v requirement to run the ADC through the motherboard probably was the Achilles' heel of the G4's.
I shorted the green on to power up the PSU.
Tested each pin by pin and gives correct output.
I guess it's either motherboard or cpu problem.
I don't want to buy both of them... too expensive.
Since you say you pulled the CPU, I would guess that would be the problem. When you power it up, does the heatsink get warm at all?
When I power up, heatsink get warm
What does this mean?
Ended up ordering motherboard from Ebay.
Let us know how it goes.
I don't mean to be a vulture but if this new board fixes the problem what will you do with the old one?
Would you be willing to part with it? /me would not mind having a dead or alive DA board to mess around with.
Now the machine boot up with BONG sound.
Red light on the board and I see box that contains "?" mark on the screen.
Still there is no light on the power button. What does that mean?
I tried the front panel to another G4 and the light comes on.
Any help here?
The blinking ? means that it is looking for a boot drive. The missing power LED means the there might be something wrong with your power button board/assembly. At least you get a startup chime and an attempt to boot, which means that the machine is pretty much functional.
It was bad motherboard. I replaced it and it works.
I don't need this motherboard so if you can pay shipping I'll send it out to you.
How do you short the green wire to power up the PSU?