Graphite iMac G3 600Mhz - No power.....

Yes, when that battery goes. no life can be a sign!
When mine went, I had no response from my Mac at all; just a light on my power button; absolutely no boot at all.
Check out things in Texas Mac Man's tutorial on the subject. His tutorial is a little dated (don't believe it even mentions G5's) but the info in it, except SMU not being included, still applies.

Cheers!
DALE

+"Can someone clarify that this flat battery can prevent the computer from showing any sign of life?"+

Dead batteries will cause all sorts of weird problems, like preferences that won't stay set, video weirdness and date problems, but one of the most frustrating is the "Dead Mac"! They just won't respond to anything.

Put a battery in, and their fine.

David

Okay i got a pink one but it still turned on with a dead battery so maybe u need a new power board as they often go

"can some one clarify that this flat battery can prevent the computer from showing any sign of life?"
I have seen iMacs start up with no battery at all and then others that won't start with a battery that has gone dead.
I think when one dies it kills the PMU. So if if doesn't start with the new battery, reset the PMU: (from Giles K)
"Reset the PMU. In the slot-loaders this can be reached from the memory access panel. With the iMac on its front and the panel open, the PMU is about an inch SW of the LH edge of the lower memory slot. It is about 7mm square and 3mm thick. The rese button on the top of the PMU is about 3 mm diameter. With the power cord removed, press it gently but firmly for about _
second. Be careful not to touch any other circuitry."

richard

That zap u here is the FBT/FLY BACK TRANSFORMER it has gone bad u can replace then but u need to know how to solder a replacement one on or u can try something easyer plug a normal monitor in to the vga port under the cover on the rear and see if it boots if not replacing the FBT is the only way to make it work

Yeah it may do if not thats the only way to fix it like i said and there is no internal fan if its a slot loader