PowerMac G4 agp tower wont boot up, no screen display but fan's running

Question

Hi all,
My G4 won't boot up. The power light goes on then off when pressed but no chime or screen on display. I hear & feel the fan running only. I reset PMU and also changed the battery but no luck. Any ideas of what it can be? Thanks for your help
Web dude

Answer 1

Thanks for the ideas MyrkridianRhapsody, but no go. It isn't booting at all.
I found a few apples sites with the following possible solutions that I will try, but my gut is telling me I fried the mother board again. I don't have the money for a new pro-mac, so I hope there is a low-cost mother-board replacement available for my 6 year old mac (any comments?).
Again, if there is someone who has successfully fixed this problem without replacing the motherboard, let me know.
As always, any additional comments/suggestions are welcome.
Will let you know my final solution.
thank you,
terry-t
Power Mac G4: Screen is Black, No Startup Tone, Drive Does Not Operate
The Power Mac G4 computer screen is black. The boot tone is not present, the drive does not operate, but the fan is running, and LED is lit.
This article covers repair procedures for authorized service providers on selected Apple products, but we have published them in the Knowledge Base for the general public for educational purposes. At this time, there are a limited number of repairs that a customer can perform and these are covered under the customer installable parts program http://www.info.apple.com/installparts. If you have not been authorized to perform these procedures, please contact Apple (800-APL-CARE in the USA) or your local authorized service provider to schedule a repair.
Symptom
The Power Mac G4 computer screen is black. The boot tone is not present, the drive does not operate, the fan is running, and LED is lit.
Affected Products
o Power Mac G4
o Macintosh Server G4
o Macintosh Server G4 with Mac OS X Server
Solution
DANGER! This procedure exposes you to high voltages that can result in death or serious injury. DO NOT ATTEMPT THIS PROCEDURE IF YOU HAVE NOT BEEN CERTIFIED AS AN APPLE-AUTHORIZED TECHNICIAN.
1. Power Mac G4 (PCI Graphics): Check jumper block at J25. Make sure jumper is correct color for processor type, includes all required inner metal clips, and is installed in correct direction. See "Processor Module" in Service Source Take Apart for more information.
2. Check video cable/card connections.
3. Reset the Cuda chip. Refer to article 95065: "Power Macintosh G4 (PCI Graphics): Resetting the Cuda Chip"
Solution
Press the Cuda reset button on the logic board to reset the Cuda chip. The Cuda reset button is located to the right of the battery. Note: If the computer still fails to power up, refer to article 95066: "Power Mac G4 (PCI Graphics): Resetting the Logic Board".
4. Reset the logic board. Power Mac G4 (AGP Graphics): Refer to resetting the PMU in article 95037: "Power Mac G4 (AGP Graphics/Gigabit Ethernet): Resetting the PMU on the Logic Board ". If you have a Power Macintosh G4 (PCI Graphics): Refer to article 95066: "Power Macintosh G4 (PCI Graphics): Resetting the Logic Board".
Procedure
1. Unplug the computer.
2. Press the Power On button on the front of the unit.
3. Open the side access panel.
4. Remove the battery from the logic board.
5. Wait at least 10 minutes before replacing the battery.
6. Make sure the battery is installed in the correct +/- direction.
7. Reassemble the computer and test the unit.
Note: This procedure resets the computer's PRAM. Be sure to check the computer's time/date and other system parameter settings afterwards.
5. Reseat video card.
6. Reseat SDRAM DIMMs. Make sure DIMMs are PC-100 DIMMs.
7. Reseat the processor module.
8. Remove all SDRAM DIMMs and try replacing them one at a time to test. Replace any bad DIMMs.
Resetting the PMU Chip Procedure
http://docs.info.apple.com/article.html?artnum=95037
a. Disconnect the power cord and check the battery in the battery holder (BT1). The battery should read 3.3 V to 3.7 V. If the battery is bad, replace the battery, wait ten seconds, and then reset the PMU (refer to the next step). If the battery is good, go to the next step.
b. Press the PMU reset switch (S1) once on the logic board. Do not press the PMU reset switch a second time because it could stop the PMU chip from responding.
c. Wait ten seconds before connecting the power cord and turning the computer on. If the computer turns on, go to the next step. If the computer does not turn on, there is something else wrong with the computer.
d. Run MacTest Pro and return the computer to the customer.
Note: This entire procedure resets the computer's PRAM. Be sure to reset the computer's time, date, and other system parameter settings before returning the computer to the customer.
9. Replace video card.
10. Replace processor module.
11. Replace logic board.
12. Replace the power supply.
It is always worth resetting the pram
as well by holding down alt-apple-p-r at the same time immediately after
booting the machine up.