iMac died after installing new hard drive

You should have checked and compare hard disk requirements in terms of power. I think your safest bet is to take it in to a Apple Repair Centre.

If there was dust still in the iMac after you installed the new HD, could some of that dust have gotten into the connectors? It doesn't take much dust to make an intermittent connection in the SATA connector or the LCD ribbon connector. You could try disconnecting the connectors and using a can of compressed air to blow out any dust.

Since it initially started up after the upgrade an intermittent connection could be an issue. If the new HD met the SATA spec, it should be adequately powered by the iMac. Plus, many NAS drives use less power than a regular drive partially due to many being 5400 RPM drives.

How "crinkled" was that ribbon connector? That is probably the most delicate part of the repair. It's very easy to damage the receptor that is on the logic board. Be sure that connector is not damaged or pulled away from the logic board.

Good luck on that. I've opened many iMacs and, although it's not difficult, they do have delicate areas such as the connectors.

Let us know how it ends, I'm kinda curious.

It sounds like something is loose to me. The fact that you could lay it on its side and get partial response but put it upright and get none implies that OR there's a loose screw in there somewhere.

One thing I've learned about Apple stuff is to make sure you put the exact same screws in where they originally came from. If you don't and one is just a little longer it may actually be touching the logic board and shorting it.

It didn't die- it's just sleeping

I've done beta testing for SCSC for just over year. They make the drive testing program Scannerz (http://scsc-online.com/Scannerz.html). FWIW, it won't do you any good to buy it but I'm going to tell you about some things I've learned during the beta program.

SCSC became aware of a problem with logic boards they call "intermittent generic faults" or IGFs. An intermittent generic fault is basically where a weak solder joint cracks and goes bad, a crack develops in a logic board trace, or a cable starts making intermittent connection because the wire in it has broken but the insulation keeps it from separating 100% and it's making intermittent electrical contact (this is the type of problem you run into when a SATA cable goes bad). If the IGF is serious enough it usually fails completely.

One of the best ways an IGF can be induced into a logic board is by flexing it. If you look at the service manual you will find comments stating not to flex, bend, or put undue strain on the logic board. The traces can crack, and if it's bad enough you will definitely have problems. That might explain why if you lay it down it "sort of" starts but you put it upright it doesn't. There's just enough contact in one orientation to allow partial electrical contact.

That might be one explanation. Another might be that some cables or connectors went bad when removed. I'm assuming you have an external bootable drive or install media, so I might suggest the following:

1. Dissconnect all peripherals connected to the logic board except any speaker connections. This would include the HDD, optical drive, all video connections, wireless, keyboard…I mean everything except the speaker. Leave the power connectors in. You don't need to remove all the devices, just disconnect their cables from the logic board. This assumes the speaker wires aren't shorted.

2. Power the system on.

Without any peripheral connected, if the problem was a cable or some type of peripheral, the system will gong and go through the steps normally needed to start up. If the logic board is OK, the system obviously won't start up because your drive is missing, but you should hear a gong and the indicator lights should give you some sort of status. This would tell you the logic board and supply is OK.

If the logic board properly goes through it's startup iterations, connect the hard drive and see if it will start. If it does, for each peripheral, turn the system off and continue plugging in each peripheral connection one by one and attempt a restart to see if you can find the one that's causing the logic board to see a problem (probably a short circuit in the cable or connector)

If it doesn't start with the hard drive, disconnect it (Power cables too, by the way) and try adding the other peripherals like I just described.

The idea of all of this is to see if the problem is logic board or supply related, or being caused by one of the other connections or peripherals.

The power regulation on most Mac's has a fail safe shutoff and if it sees a short circuit in one of the output lines, instead of turning on and toasting the system, the supply cuts off, and of course the system won't start. The solution is to remove the short circuit. Any short, even if it's caused by something on the logic board making contact with ground, like a shield or a screw, can also cause the problem.

If the logic board shows no signs of life with everything disconnected then either the logic board or supply are at fault. Look at any and all of the connectors that were removed. Sometimes if a pin connector is installed quicky, if one of the pins isn't properly in it's connector it will bend over causing a short circuity. That can be fixed by carefully bending it upright (with the power off of course) and reinstalling the connector. This problem used to happen a lot of the old IDE drives.

If the system shows no signs of life even with everything disconnected I would still look at all the connectors carefully, but it would imply the supply or logic board is having problems.

A Mac doesn't need peripherals connected to it to go through it's initial startup phases, but with no drive connected it obviously won't boot up.

Another possibility might be an electrostatic zap occurred during work and it fried the logic board. Most circuitry these days is protected against that but it can still happen.

In any case, good luck.

You caught me at my desk right now so I was able to see this quickly.

Yes, pull the video card too. You may have to additionally elevate any internal cables so they aren't making contact with any grounded surfaces or laying across the logic board. Once and only once did I see an audio cable cause problems. It was on an old PowerBook G4 and one of the sharper solder connections dug into the audio cable causing it to short because they had it routed right on top of the logic board. You may need to disconnect the audio cable from the logic board but you'll hear no gong sound and have to rely solely on the status light.

I think right now all we want to do is see if the thing will power up at all and show any signs of life and/or intelligence.

I think your logic board blew. The darkened area indicates board damage. Looking closely at the logic board photo it appears that several traces are blown. It's tough to tell with a photo.

I'm not sure you did anything wrong. I think it's quite possible that when you installed the drive the board decided to head south a few minutes later coincidentally. it may have absolutely nothing to do with the hard drive or the work you did.