Question about a used iMac Intel

Never saw caps do lines in displays. But Nvidia had a rash of bad GPUs in the 7 series, especially mid-range.

I work on a bunch of these. The lines is a very common problem on the 17" intel, this is a problem with the screen, replacing the screen will fix the problem, it's not the video, unfortunately as far as I can tell there is no reasonably priced compatible replacement screen that does not have this problem. I don't know if this was fixed later, but I've seen it on the first and second gen white imac 17" I've had the fewest problems with the aluminum ones, but maybe they just haven't died yet. I have seen vertical lines, although on those it's usually 1-2 lines that you may be able to ignore, not the whole screen eventually turning to lines as it is with the 17". As least I have yet to see one with more than a few lines. If you see an ebay listing, post it, I'd be interested to see.

The 20" often have bad video, this seems less common on the 17", although I have seen bad video on the 17" ones as well.

I see so many problems, I couldn't recommend one of the white imacs to a friend, and would suggest either the aluminum or mac mini.

With LCDs, bad caps generally means no video at all, and especially no backlight. Given that and the relatively low age of the Intel Macs, I think it's likely you're looking at some other hardware issue.

Smiggly, in your experience is there a common point of failure? Ribbon cable, BGA like the ibooks, etc.? I've got LCD repair experience, but am not familiar with iMac hardware post-PPC.

Unfortunately, I don't think you're going to get a clear answer

I see several hundred imacs a year (working and not working) and just make note of what I see coming off warranty. I personally work on about 100 a year, but only after the warranty expires. What I don't know is how many were repaired under warranty. The extended replacement on the 17" screen only recently ended, so I can only assume many have already been replaced by apple. I can often tell when Apple replaced the board on a G5 iMac, but don't see any signs on the Intel ones.

I honestly don't think any of the 2006 iMacs are more reliable than any others. The failure rate seems to be pretty high. I hold that heat is the root cause of most of the iMac problems, there just isn't enough airflow. Keeping them free from dust and with good airflow around them so they don't overheat is probably the best way to keep them lasting a long time. If you're going to ask me which I'd suggest, it would be neither, instead I'd suggest a Mac Mini, or going for the aluminum ones which seem to fail less often (as a bonus, they are much easier to work on). I've seen far fewer problems with Mac Minis than any of the 2006 iMacs, although the cost is probably a little higher after buying the screen. If I had to pick between the 17" and 20" iMacs, it'd be the 17" one. My guess is the failure rates are a little higher on the 20", but pretty close to the same. I'd pick the 17" since I'd rather do a screen than the board (easier to replace, possibly cheaper)

Not sure if this is what you're asking for, but here's a list of the most common problems to watch out for with each
G5 17/20 - Bad Capacitors (board and power supply)
2006 intel 17" - Bad display
2006 intel 20" - Bad board (video ram?), bad power supply (maybe 1/5 bad ones I see have a bad power supply, the rest are board)

On the 17" intel iMacs the only major problem I've seen affecting more than a few would be the lines on the screen. I have no idea what causes this, I've seen one that started showing lines within the first year. I believe this is a design flaw in the LCD. I don't know anything about repairing the actual panel itself, it's not the removable cable, I've read that it has to do with some of the internal connections. The screen is the "LM171W02 (TL) (B2)". As I recall, Apple stated this was only a problem with the ones starting with W8, however I've seen just as many QP ones with this problem, so I don't think it has to do with that particular factory. I've noticed no difference in first and second generation (early vs late 2006). When this starts it seems to be just a single line that shows up for a few minutes after booting, then disappearing, within weeks it becomes more permanent, and it just continues to get worse with more lines. If you are thinking of buying one, check it immediately on booting to make sure there's no lines (often they are gray, and hard to see), do not buy if you see anything. The most interesting fix I see for this is this adapter that will allow you to use a different screen: http://www.realmacmods.com/ This is something I've really wanted to try, and absolutely what I would do for myself/friend as I think this would have the best chance of being a long term fix as you could research and find a known good panel to use as a replacement.

On the 20" the only major problem I've come across is related to the board. I haven't really looked too much into this, but would love to know if anyone knows the root problem here. Since most problems seem to start with artifacts on screen, I think the problem is related to the video RAM. I've also seen the power supply go on several, although not nearly as common as the board. I don't recall ever seeing lines on the 20" iMac. I don't like working on these, because the problems can be difficult to detect, sometimes it won't show, but the next day it won't boot. Generally it seems they work well, then all of a sudden you'll start getting random crashes/artifacts. Generally I've found increase the fan speed and continue will prevent the problem, and allow you to keep using the computer for awhile, but my experience is if the problem starts, they will eventually fail. As far as I know only the 24" have nvidia, I have only seen a few of these (so far none dead), but I don't have enough to say whether these are good or bad. I have about 30 20" ones to go through over the next few weeks, I'll try to note the problems with them as I go through to see, if you've got anything you want me to watch for, let me know. If you buy one of these, run a video or something to make sure you stress the video card/ram as much as possible and watch for artifacts. If you see anything, this one is going bad.