With regard to a recent thread on G5 iMac capacitor replacements, here are some things I've learned, now that I've replaced the capacitors in three first-generation iMac G5 computers. My record so far: 1 win, 2 losses.
The win was a 20" 1.8 GHz first-generation G5 iMac that still chimed and booted, but shut down, very hard, with many video artifacts after 15 seconds of running. I replaced all the caps in the power supply that Jim Warholic suggested at his web site, and all 25 on the logic board. There was a period of several days after replacement where occasional minor video glitches of a very brief nature happened a few times. This happened less frequently each day until there were none at all. I'm calling that a burn-in period. Then my grandson took it home and used it for a couple of weeks. Suddenly last Friday, on the first start of the day, it chimed and booted. Then the display exhibited all kinds of weird video artifacts, it beeped loudly three times and shut down hard. Both RAM sticks had died, simultaneously. I replaced them, did some Open Firmware magic finger tricks on the keyboard, and it booted and ran normally again. It also passed both Apple Hardware Tests as well as both Apple Service Diagnostic tests, Drive Genius 2 hard drive tests, and the while- booted Tech Tool Deluxe tests. All of this took hours, with the fans running at full tilt. It then ran without a problem for two days and now is back at his place, looking quite innocent but with its white chin stuck out in quiet defiance of the odds. My guess is that the generic RAM sticks (2 x 512 MB) were damaged during the original series of problems that led to the failure to boot and run normally. Probably power surges or fluctuations caused by the bad/dying capacitors weakened them, and they couldn't handle the stress of running "normally" for very long after the cap replacements. I'm keeping my fingers crossed that the second pair of RAM sticks don't go belly up several weeks from now. :^) The two losses were also 1.8 GHz iMacs, one 17" and the other 20". Both had crashed hard and refused to start. The 17" wouldn't even turn on the front panel light; the 20" did, but that was all. Each had the same five bulging/leaking caps on the logic board, and more than half the caps in both power supplies were bulging/leaking. I replaced caps on both logic boards and power supplies. When power was plugged in with the back panel/stand removed, the first diagnostic green light on the logic board came on in each one, indicating the logic board was "seeing" the correct power. When the on-board power/start button was pushed, the front panel light came on and diagnostic light no. 2 flickered briefly, but nothing else happened, with one exception. That exception was with the 17" iMac, where the hard drive began running. But light no. 3, which indicates the logic board is talking with and sending energy to the LCD, never came on. I swapped the good power supply out of my grandson's 20" G5 into the other 20" G5, and it showed the same symptoms as the 17" on attempted starts, with the hard drive running. So the second G5 power supply has problems that were not corrected by capacitor replacement. Neither of the loser iMacs chimed, nor did the optical drive do that zingy noise thingy, nor did either light the LCD. My conclusion is that a power surge or other uncontrolled electrical charge zapped both logic boards in the run mode (diagnostic light no. 2 circuit), and possibly in the LCD power circuit. However the inverter from the bad 20" did work in the good 20". So, FYI, if you're going to try the capacitor replacement trick, you'd better do it while the iMac's still able to chime, boot and run, even if only briefly. Otherwise, you're very likely going to be left with a substantial pile of usable parts, and good capacitors that have to be removed (aaaarrrggghhh!). -- Jim Scott --~--~---------~--~----~------------~-------~--~----~ You received this message because you are a member of the iMac Group, a group for those using Apple iMacs and eMacs. The list FAQ is at http://lowendmac.com/imac/list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/imaclist -~----------~----~----~----~------~----~------~--~---
