Need to reset PMU on AGP G4 everytime I power up...........

Question

.......otherwise the monitor won't come on.
I have had this same hardware setup for years. A 32MB AGP video card, system profiler below and a 450 MHz AGP Mac upgraded with a 1.4 GHz processor from OWC.
Tried to upgrade the video card recently to a 128 MB unit, but I didn't have the extra power cable required so I went back to the existing video card.
After that, the Mac would not start at all - no power nothing.
After some other checks, I eventually reset the PMU and then Mac then started fine.
But now, after I shut the Mac off, it will come one when I hit the power button, ie power light is on, fans are spinning, but the display stays dark.
When I query the display (pushing the "+" button on it, it tells me the Mac is in the sleep mode. However, moving the mouse or operating the keyboard doesn't wake it up.
If I then power down the Mac again (by holding down the power button), reset the PMU again, the Mac powers up OK next time around and the display come on.
I went through that scenario twice so far.
I usually leave the Mac running 24/7, so maybe this is an older problem which I never noticed, but does anyone know what is going on? Or better yet how to fix this.
I haven't tried resetting PRAM - would that help.
The battery reads around 3.4 volts in the holder; it was replaced once. Any possibility that could be the issue?
I don't want to experiment too much without some specific focus since I keep hearing that resetting the PMU too often is not good. No idea why that would be however.
Chipset Model: ATY,RV100
Type: Display
Bus: AGP
Slot: SLOT-A
VRAM (Total): 32 MB
Vendor: ATI (0x1002)
Device ID: 0x5159
Revision ID: 0x0000
ROM Revision: 113-85501-208

Answer 1

I want to pick up on this thread again.
I keep the mac running 24/7, so the display not coming up when I power up was not a really big problem. I had hoped that replacing the battery would solve this issue, but it didn't.
I bought a brand new battery, checked the open circuit voltage before I replaced the old one, but I still have the problem.
The oen circuit voltage on the new battery is 3.62 volts; the open circuit voltage on the old one was 3.66 volts - both well within specs. The minimum voltage Apple specifies is 3.3 volts, so I'm well within specs.
I wonder if in the time since my initial post someone else has had this problem and found a solution other than the ones that have been linked to or are available via a google search.
Problem briefly:
When I shut down the Mac and then restart it, the Mac powers up fine but the LCD display does not come on. When I query the display using the display buttons, it tells me there is no video input. This display used to work fine; if I use a different AGP G4, the display powers up fine automatically, so my conclusion is that this is a Mac and not a display problem.
The way to bring the display back is to power off the Mac by holding the power button down, open the case, push the PMU reset button once, close the case and hit the power button.
If I only restart the Mac, the display goes off (as it should), the LED indicator on the display goes into the power down mode (orange instead of green), but when the Mac then restarts, the display comes on fine. The Mac in this situation of course never turns off completely.
Does anyone have any other ideas what to try - I'm tempted to get another logic board.