ALS or non-ALS identify and blank screen

I just bought a fixer upper imac, it was sold to me as the g5 1.8ghz but I am wondering if it is the ALS version. There is only one button below the upper fan, and I thought on the non-ALS version there was two (one to turn the mac on, and one to reset the smu). Also, there IS the ALS hole in the botto of the case, which leads me to believe it is the ALS version). I bought a power supply as the imac didn't come with one (fixer upper, remember), and I did NOT buy as ALS specific powersupply (it was part #614-0366 that I bought, which I see is compatible with ALS imacs). Would this prevent the imac from booting? I replaced and have reseated the ram, and replaced the hard drive. I cannot get the computer to boot, just the chime, status light solid, and a blank screen, although if I turn the lights off I can see the lcd lit up a tiny bit. Should I replace the lcd, or could my problem be the 7 caps that look bad on the motherboard? When I turn on the computer with the back off, I do get the first 3 lights up on the mother board (kinda below the upper fan). To summarize:

1. would a non als specific powersupply prevent the imac from booting (I have not installed osx yet) 2. does a dim screen indicate at this moment a bad lcd, or 3. would bad caps on the motherboard prevent the imac from even lighting up the screen. Thanks in advance, I am pulling out my hair!

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It sounds to me like it would be the capacitors on the logic board that are causing the issue. If it has the one button on the logic board and it has a small hole with a bubble coming out of it on the bottom vents then it is the ALS model. You can also put the last 3 digits of your serial number into this website and it will tell you what model you have:

The symptoms that you are experiencing sound like the common capacitor issue with these models. You can finds kits that have all the capacitors for the computers so that you can replace all of them at once. The reason that they fail is because of time. It is best to replace all of them even if only a couple look like they have problems. Get back to us with your results.

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Hi, thanks! This imac came to me with the serial sticker on the bass torn off. so I just went with what it was sold as. I am now pretty convinced it is the ALS version (which is ok as it is faster, a bit). The new powersupply I installed is for non-als imacs, so doesn't have the little bubble sensor on it, so there is no "bubble" in the hole as seen from the bottom of the case. Just an empty hole. I found another thread where a list of powersupplies and imacs were compared, and the one I bought, thankfully, is compatible with the als, even though it was sold as non-als. Yes, I do have 7 slightly bulging caps, no leaks but I am figuring that is wha it is. I've done plenty of soldering lately, as I got into rc planes so am not scared of doing the cap replacement, just wanted to see if I was on the right track. Thanks again, any more suggestions? Has anyone had trouble replacing the caps?


There actually are speaker intake holes on these iMacs on the bottom which may be making it confusing to identify. I had a 2.0 ghz g5 that had 4 bulging caps so I just replaced the 4 and it still didn't work. I ended up buying a set (I will se if I can find a link for you) of all the logic board capacitors for $30. Only after I replaced them all did the iMc work as it has been for almost a year and a half now. The only problems that I ran into is that most replacement caps are taller than the originals so you have to make sure that you get them as close to the board as possible. The solder on these is also nonleaded so it takes much more heat to desolder them from the board. You may, like me, have to get a higher temperature soldering iron. The replacement though is pretty easy if you know what you are doing. There are plenty of guides on YouTube for this replacement as it is a very common issue.


Also, when you say that there is no bubble in the hole you may want to find your old power supply. The small board with the ALS bubble is attached to the power supply and will need to be transferred. 


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Over the weeks I have become intimately experienced with these imac g5's. Yes, the problem was the caps. I now have recapped a dozen of these imacs, with a tidy profit to boot. Very easy fix, especially if you use the "chipquick" product from Jim. I am now moving on to fixing intel iMacs, but they are a pain in the %^$ - too bad apple had to make them so un-user serviceable.

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