I am having a problem of getting only momentary power to my iMac (G3-slot loading), and am wondering what I need to replace (logic board, power supply, etc.). M5521 - SN RN0018N2HTH 350MHz/512 L2/64MB (upgraded to 128MB) 6GB/CD/56K/BB The symptoms are that when I depress the power button, either on the keyboard or on the cpu, the power light on the Mac and the lights on the keyboard come on for only a fraction of a second and then go off. If I hold down the power button continuously, once and awhile the lights will flash on and off several times, and then I might hear the screen crackle momentarily or the hard drive start to spin up. However, the system does not start to boot (no 'dong'), even if I release the power button as soon as I hear either the screen or the drive start. This happened a couple times before about a month ago. Repeated attempts over a one hour period finally succeeded in powering on and booting the system, but not this time. This afternoon I replaced the lithium battery on the logic board, but this did not help. This appears to be OS-independent, since it has occurred with both Mac OS 10.1.2 and with Debian Linux (either installed as the sole OS). This is a power issue and not a boot issue, as the system barely begins to even power up and does not get to the point of starting a boot sequence. Any suggestions would be appreciated. Thanks, Barry Skidmore

I just tried resetting the CUDA switch on the logic board, but this was without effect. I did it a second time, and then put in another new battery, but the problem remains. Any other thoughts? Barry

I would start with the power supply. Typically if it was the logic board, you would have other signs of power issues on the board (burned traces or caps etc...)

I agree with WAG, check the power supply. I had the same problem with a G4 tower. I would start with the button and the button would come one, then go right off when depressed. Changed the power supply and it fixed the problem. they are cheap too.

Dont know if that machine has a reset on the rear apron or not, but if it does, the reset might be faulty or just dirty. I had the same problem on a PB1400. The reset had become flakey. I finally became desparate and shot a little WD40 into the reset switch. It worked. And what the hell, my warrantee was long since expired! Jon %00

This sounds like the infamous "stuck power button" issue. The early slot-loading iMacs are prone to having the power button under the monitor stick. You can try popping it out a little with a paper clip (doesn't work too often), or see this page: http://www.scienceman.com/pgs/ archive26_imacpower.html And use the keyboard switch!