It could very well be the PAV board is bad (Power Analog Video).
If you look straight down from the top mid-rear of the iMac, right where the small holes are located around the handle, you'll see the the electrical cord's connector is attached to the big circuit board underneath the picture tube (CRT). THAT circuit board IS the PAV. It is essentially the main bridge of electrical power for the iMac; It suuplies power to the logic board, down convertor board and picture tube.
This is a common problem in CRT-based Macs. One way to tell it's nor working is after adding power to the iMac, it tries to turn on for a second, but shuts off. Also, a high pitch whine coming from the inside the computer. A new board will cost around $300-$400 USD, not including labor and tax.
It could also be the down convertor board that has gone bad.
This small board is attached to the logic board and PAV board, located underneath the iMac. It is there to supply low-voltage to the logic board and also to the hard drive. I'm not sure how much a new board costs, but I know it's much cheaper than a PAV.
The logic board could also be faulty. This one is obviously located underneath the iMac. This is another part known for failure, but on a rare occasion. This board, like all other logic boards, detect when the power button is pressed and runs a quick POST test (Power On Self Test). The cost to replace a logic board is fairly expensive, around $400 to $600 USD. At those prices, I would just opt to replace with a newer Mac.
73s 8)
If you look straight down from the top mid-rear of the iMac, right where the small holes are located around the handle, you'll see the the electrical cord's connector is attached to the big circuit board underneath the picture tube (CRT). THAT circuit board IS the PAV. It is essentially the main bridge of electrical power for the iMac; It suuplies power to the logic board, down convertor board and picture tube.
This is a common problem in CRT-based Macs. One way to tell it's nor working is after adding power to the iMac, it tries to turn on for a second, but shuts off. Also, a high pitch whine coming from the inside the computer. A new board will cost around $300-$400 USD, not including labor and tax.
It could also be the down convertor board that has gone bad.
This small board is attached to the logic board and PAV board, located underneath the iMac. It is there to supply low-voltage to the logic board and also to the hard drive. I'm not sure how much a new board costs, but I know it's much cheaper than a PAV.
The logic board could also be faulty. This one is obviously located underneath the iMac. This is another part known for failure, but on a rare occasion. This board, like all other logic boards, detect when the power button is pressed and runs a quick POST test (Power On Self Test). The cost to replace a logic board is fairly expensive, around $400 to $600 USD. At those prices, I would just opt to replace with a newer Mac.
73s 8)