IMac 17" Hard Drive and DVD dead after install.

Question

I am attempting to install a WD 250gig hard drive into a 17” flat panel 800mhz imac. I followed the directions of taking the base apart and installing the new drive with great care. The Original 80 gig drive was set to master and the DVD drive was set to slave. I set the new WD drive to master and put the base back together. All I got was a flashing question mark. That was not unexpected, but I have been unable to get the iMac to recognize the existence of a hard drive or the DVD superdrive. I started the iMac from my Powerbook in firewire target mode. And verified that the iMac does not see the drives within the system information or the Disk Utility.
I have tried resetting PRAM, changing the jumpers on both drives, making the DVD master and the HD slave, setting the HD on cable select. Formatting the HD in my Powermac and cloning the original HD to it with CCC and replaced the ribbon cable. I now can take this iMac apart and put it back together faster then a Chinese factory worker.
I have abandon hopes of a new hard drive and put the 80 gig back in exactly as I found it. The iMac will not recognize the original configuration either. I started this project as favor for my sister who owns the iMac. There is not a lot of money here to send the whole works into service.
Does anyone have any ideas on what went wrong?
Is there a way I can test the power supply to the drives?
imac 17" FP 800 mhz   Mac OS X (10.4.7)  

Answer 1

Well we figured it out. DO NOT TRY THIS AT HOME. Since nothing we did worked, I figured we had nothing to lose. With the assistance of my electronics wiz brother, we powered up the iMac while having the base opened and the components spread out on a table. Using a voltmeter, we determined we were only getting 3.6 volts to the drives. It should have been 12 volts. Somehow, something went wrong with the system board. After careful examination under a magnifying glass and some prodding with a voltmeter, we discovered that a tiny component next to the power connector on the system board fell off. It was no more than 2mm across and was marked (L13). We figured this was an inductance component and probably a filtering device for the power to the drives. We powered up the board and jumped the leads with a screwdriver. The HD and DVD fired right up. A careful soldering across L13 made the fix permanent. I got it all put back together and everything is running great.
The moral of the story; be extremely careful when pulling connectors off the system board. I must have knocked the component off when I first took the iMac apart. I just got lucky we found out what it was and were able to find a quick fix.
This a nice little iMac, but i never want to work on one again.