[drmcnutt]

I tried to look through many of the similar threads and I appreciate any help regarding this. I've had a G4 out of commission for some time now. I turned it off using the power button instead of shutdown once and it hasn't come back. When I press the power button I get a flash, but earlier advice (resetting the PRAM. replacing the battery on the logic board) failed to work.

I recently purchased another logic board through eBay. It's used, but has a 60 day return on it. When I replaced the logic board I get nothing at all in response-no flash of light period. I have a processor upgrade and read that the firmware may not support it so I tried the original processor too. Nothing. If there is any advice someone could give me I would sincerely appreciate it. Stuck for now.

[Cold Warrior]

In this situation PRAM is a good first start but probably not the root of your problem. Sometimes a PMU reset can fix your issue. Apple's instructions on that are pasted below from this article in full:

Resetting the PMU Chip Procedure

1. 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.
2. 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.

3. 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.

4. 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.

[drmcnutt]

Thanks for the fast response. Maybe my terminology is off. I did press the PMU button (several times in different tries-is this the PRAM as well?). And actually today I did what you describe here, took the battery out. I don't know how to tell if it is good or not. Before I bought the logic board I just installed I did borrow a working battery from another mac I have access to. My result wasn't any different.

I'm presuming the logic board came with a battery that works (it was in the description) I'm confused by the different symptoms for each logic board. My old one has a flash when I depress the power button, the new (presumably working) logic board does nothing. I wasn't imagining it would get worse with replacement.

Thanks again for the fast response. I might try it again using the two batteries I have handy.

[Crimson]

Just curious, have you checked the cable that goes to the front panel board? Both ends...

[drmcnutt]

Thanks for the reply. We took a measurement off the power supply and the voltage is not up to where it is supposed to be. Thanks for the tips. I replaced the power supply before, but it looks like I need another one.