Late 2006 iMac will not power up without PRAM (CMOS) battery reset!

[brettjameslive]

Okay, so I have a late 2006 Intel based iMac, same model as here: http://www.ifixit.com/Device/iMac_Intel_20"_EMC_2105_and_2118

It failed, so I replaced the RAM, amongst other things. I have the front bezel off, so I have access to the front of the logic board underneath the screen. If I unplug the computer, remove the watch battery (the PRAM battery I believe?) and leave it for 15 seconds (CMS reset), then replace the battery, and plug it back in, it powers up, and boots fine.

Shut the iMac down, and try to switch back on, nothing.

Repeat the CMOS/PRAM battery and power removal procedure, and it works!

Any ideas why this is? It's not practical to do this each time, as I want to put the screen bezel back on!

I have also done a PRAM reset and changed the actual battery several times.

A note, from the OS, a 'Restart' works fine. It's just if I select 'shut down' it won't turn back on.

 

[Markverhyden]

Just to be clear. You have tried different cr2032 that is new?

Also did you try this?

_SMC RESET_

• Shut down the computer.
• Unplug the computer's power cord _and all peripherals_.
• Press and hold the power button for 5 seconds.
• Release the power button.
• Attach the computers power cable.
• Press the power button to turn on the computer.

 

[anonymous Mac Tech]

Okay, so I have a late 2006 Intel based iMac, same model as here: http://www.ifixit.com/Device/iMac_Intel_20"_EMC_2105_and_2118

It failed, so I replaced the RAM, amongst other things. I have the front bezel off, so I have access to the front of the logic board underneath the screen. If I unplug the computer, remove the watch battery (the PRAM battery I believe?) and leave it for 15 seconds (CMS reset), then replace the battery, and plug it back in, it powers up, and boots fine.

Shut the iMac down, and try to switch back on, nothing.

Repeat the CMOS/PRAM battery and power removal procedure, and it works!

Any ideas why this is? It's not practical to do this each time, as I want to put the screen bezel back on!

I have also done a PRAM reset and changed the actual battery several times.

A note, from the OS, a 'Restart' works fine. It's just if I select 'shut down' it won't turn back on.

Was the startup issue what the machine came in for?

 

[brettjameslive]

Yes, the only way I can get it to boot, it reset the CMS. In fact, I am leaving the 2302 (which I have replaced with new 3 times just to be sure), out of the machine now, and an SMC reset is the only way it will boot. Note, if I leave the battery on the board, an SMC WONT work.

And yes, the power issue was the original issue. It used to just show the white light, nothing else, so I replaced the RAM and it booted fine, then, this happened! Although it has to be said, I am not sure if this would have occurred without the RAM replacement. The new RAM is good.

 

[anonymous Mac Tech]

Yes, the only way I can get it to boot, it reset the CMS. In fact, I am leaving the 2302 (which I have replaced with new 3 times just to be sure), out of the machine now, and an SMC reset is the only way it will boot. Note, if I leave the battery on the board, an SMC WONT work.

And yes, the power issue was the original issue. It used to just show the white light, nothing else, so I replaced the RAM and it booted fine, then, this happened! Although it has to be said, I am not sure if this would have occurred without the RAM replacement. The new RAM is good.

I ran into a 2007 iMac a week or two ago with a similar issue. All you can do is disconnect everything and see if the same issue still happens. I swear it's almost as if some Apple hardware hits a certain age and just completely craps out. Like it has a timer to crap out when age hits ...