iMac G5 Logic Board

[Mithrandir]

So my family used an iMac G5 as our one and only computer for many years. In fact, my mom bought it like a week before the intel macs came out (even though she has been buying macs since the late 80's she isn't exactly an expert on the hardware side of things). It worked great until it broke about 4 or 5 years ago. It was taken in to the apple store, and they told her since it was so old that it would be better to just get a new intel mac, so that was what she did. Apparently they told her the problem was a dead video card. Now she wants to get some old photos off the hard drive from this mac but since it doesn't work she was going to pay some tech guy she knows $250 to get the files off of it. I told her that I could do better than that though. Now I need your help.

Ok here is where all the good stuff is. So I know I could probably remove the hard drive and put it into something like my powermac g4 to get the files off. but I think it would be way cooler to get this iMac up and running, and my Mom said it would be okay as long as I could do it for $150 or less. So when I turn on the machine I get a single startup chime (like normal) and I hear the computer whirr to life. The indicator light lights up, and everything seems to be working fine except the display does not turn on, ever. Now going off of what the apple store people said (and my mom's memory...) the computer has a dead video card, would that cause these symptoms? Another thing I have tried was to hook up a usb keyboard and try the shortcuts for resetting the PRAM and target disk mode. Those don't seem to work either...

Ok onto the options. Now I read that the video card is a part of the logic board, so looks like I need a new logic board correct? The iMac is an iMac G5 20" 2.0ghz model. Now I found this listing on eBay that says the board comes from the same model, do I have to look for anything else or will the logic board work for sure in my mac. I know it might be a bit expensive but this one is GUARANTEED to work, or I can return it. The others are just as-is. http://www.ebay.com/itm/APPLE-iMac-G5-2-0GHz-20-Logic-Board-820-1747-A-Motherboard-System-Board-TESTED-/380456401466?_trksid=p5197.m1992&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3D1%26asc%3D14%26meid%3D817411378022621396%26pid%3D100015%26prg%3D1006%26rk%3D1%26#ht_632wt_1413

Finally, do you think that I could replace this myself? I found a video on how to take out the logic board from an iMac g5, so could I also so it in reverse to install one?

Thanks in advance for all your help I never would even try this without 68kmla to help me out a bit.

 

[Gary_W]

You will need a special tool to separate the bezel from the back. Luckily I found this info on how to make one out of an old gift card and it worked like a charm:

Good luck!

P.S. I was able to recover her photos (no backup, from 2006 to present) by plugging the iMac's SATA drive into my Windows XP box and using software called Transmac to copy stuff over! It has a trial period and it worked great. The disk could not be tested with spinrite either, just thunked a bunch of times and that was it.

 

[mcdermd]

Does this iMac post (go "bong" when you start it)? If so, the video processor is probably fine.

I've had iSight iMac G5 models with bad capacitors also. They were on the bottom (back) side of the logic board in the middle. A little work with a soldering iron and a few dollar's worth of caps revived it.

 

[Gary_W]

I was thinking the one I am working on may be a bad cap issue too. I guess I will have to pull the logic board and find out. Not sure I want to get that far into it.

 

[Mithrandir]

if i post some pictures of the logic board could you guys maybe help me identify a problem. I really don't know what I am looking for here. Thanks

 

[Mithrandir]

Ok here are some pictures with the back off. The problem is that none of the videos on how to disassemble an iMac look like mine in the back. Im a little confused about that. Anyways if you need more detailed pictures of a certain area let me know.

P.S. I already removed the ram

 

[mcdermd]

That looks like an iMac G5 ALS (Ambient Light Sensor). ifixit.com has a guide.

I don't see any bad caps on the logic board. The power supplies in them go bad due to failed caps, though.

The big question is - does it go "bong" when you turn it on? Any lights? Fans?

Under the top fan by the optical drive is a button on the logic board. That will allow you to turn it on with the back off. Near there you will see four diagnostic LEDs :

• LED 1 indicates that trickle voltage from the power supply has been detected. This LED will be ON when the computer is turned off and your power supply is working correctly.• LED 2 indicates that the main logic board has detected proper power from the power supply when the computer is turned on. This LED will be ON when the computer is turned on and the power supply is working correctly.

• LED 3 indicates that the computer and the LCD display are communicating. This LED will be ON when the computer is turned on and video signal is being generated.

• LED 4 lights only if the computer detects an over-temperature condition. This LED will be OFF when the computer is turned on and running at the correct temperature.

 

[Mithrandir]

Ok so yes, the computer bongs whenever it boots up. I did that thing with the lights, and only lights #1 and #2 light up. Light #3 stays off as well as #4. So would this further prove my theory of a dead video card or would it mean something else? Are there some steps I should try in order to fix it? Oh yeah and the fan does turn on, the only thing that is wrong is that the display stays black.

 

[Forrest]

I see some suspect capacitors in the second picture. You'll need to take close-up pics to confirm.

Have you tried attaching a secondary monitor to the monitor port? Do you get a picture?

 

[mcdermd]

The power supply may also have bad capacitors. I had a G5 that looked good but wouldn't light. I think the problem was the power supply wasn't pushing enough power to bring up the display. I replaced the power supply caps and it was fine. If you're so inclined, you may want to have a look for any bulged or leaking capacitors inside the power supply.

 

[ianj]

1. Get this.

2. Use it.

3. PROFIT

 

[techknight]

oh yea, i love those things.

if you send me the G5, i can take it to work and I MAY be able to revive it on the IR rework station. its possible the caps in the power supply MAY be bad, but i doubt it. The caps on the logic board look perfect. If LED#1 and #2 are on, thats telling you that the logicboard sees the standby power, main power, and all voltages are present and stable. if you hear a unsettling hiss from the power supply then i would worry.

Anyway, the 3rd LED means the Video chip is initialized and LCD/GPU is communicating. Since this stays off, that means either the logic board cant see the LCD display's EDID, or the video chip has come loose from the board or went bad.