I've got this iMac G3 DV 400 that turns on, I hear the high-voltage crackle, chimes, green LED, trickle voltages are fine, etc. But after around 6-8 seconds of being on, as the CRT is supposed to start showing an image, it turns off, and I hear the HV parts crackle like high voltage electronics usually do when discharging. When I turn it back on, the green LED stays on but nothing happens, no chime, and some of the voltages that are on the DCB pins are a bit lower than they're supposed to be according to the service manual, and it doesn't return to how it is during the first example until I unplug it for a few seconds, then plug it back in.
It used to boot to the "no boot drive" screen on an external monitor (it's missing a HDD, so this isn't a hardware issue or anything), so it turned on before, but the CRT never started showing anything, nor did I feel static on the screen or hear the high-pitched whine. Opened it up once to take a look inside the disc drive, upon reassembly it started doing what I described earlier.
I've seen some posts with other issues that have been suggested to maybe be a flyback issue, but there's no arcing, and I hear a high-voltage sound from the PAV area so there's atleast some high voltage there. And as it was produced not too long before the capacitor plague (very early 2000 if I read the serial number right, week 3 iirc), and a dead capacitor might be preventing the FBT from getting the power it's supposed to, causing it to turn itself off. But I have very little knowledge on all this so maybe someone here has had a similar issue.
EDIT: Forgot to mention it, but I've tried resetting the PRAM several times via pressing that button on the MB, PRAM battery is also just fine, according to my multimeter it outputs 3.68V, and it's brand new. It's also in the correct orientation. External monitors also get a signal for a split second before it turns itself off, can't see exactly what though as it's outputting an incompatible resolution after a PRAM reset. ("Out of Range Signal")
It used to boot to the "no boot drive" screen on an external monitor (it's missing a HDD, so this isn't a hardware issue or anything), so it turned on before, but the CRT never started showing anything, nor did I feel static on the screen or hear the high-pitched whine. Opened it up once to take a look inside the disc drive, upon reassembly it started doing what I described earlier.
I've seen some posts with other issues that have been suggested to maybe be a flyback issue, but there's no arcing, and I hear a high-voltage sound from the PAV area so there's atleast some high voltage there. And as it was produced not too long before the capacitor plague (very early 2000 if I read the serial number right, week 3 iirc), and a dead capacitor might be preventing the FBT from getting the power it's supposed to, causing it to turn itself off. But I have very little knowledge on all this so maybe someone here has had a similar issue.
EDIT: Forgot to mention it, but I've tried resetting the PRAM several times via pressing that button on the MB, PRAM battery is also just fine, according to my multimeter it outputs 3.68V, and it's brand new. It's also in the correct orientation. External monitors also get a signal for a split second before it turns itself off, can't see exactly what though as it's outputting an incompatible resolution after a PRAM reset. ("Out of Range Signal")
