Q: New iMac 27inch screen flickering/tearing/shutoff

Everyone is talking about their machines being week #, etc. (i.e., week 47). I would appreciate it if someone would tell me what that means and where that information is found.

As an aside, I am one of those folks reading this thread to decide when to buy a i7 27". I will not until the issue is clearly understood.

Well of course, the vital missing parameter in all this "my Fan is working better than yours Who-ha" is AMBIENT AIR TEMP?

Clearly one of you lives inside a fridge - whereas the other lives elsewhere. Your iMac fans can only use ambient air - to facilitate cooling and so, your ambient air temp. has a large effect on how fast your fans are directed to spin at.

NULCGI wrote:
Well of course, the vital missing parameter in all this "my Fan is working better than yours Who-ha" is AMBIENT AIR TEMP?

Clearly one of you lives inside a fridge - whereas the other lives elsewhere. Your iMac fans can only use ambient air - to facilitate cooling and so, your ambient air temp. has a large effect on how fast your fans are directed to spin at.

My ambient air temp is linked in my original fan post (right now it's 18˚C). But ambient air temp doesn't explain why Simon's fans are spinning slower than the minimum-allowable fan speeds as set in firmware...unless, of course, his firmware settings (which aren't user-adjustable, AFAIK) are different than mine were for my last two 27" i7 iMacs.

Obviously ambient air temperature has a significant effect on fan speed. But that's not at the heart of the point I was trying to make in my "who-ha" post. I guess the going-in assumption around here is that the average Mac user has a double-digit IQ -- else we wouldn't need to have the effects of ambient air temperature on fan speed pointed out.

Message was edited by: Schwa72

My fan speeds are 939/1100/998 and never fluctuate more than a couple of rpm regardless of the internal temps.

Just downloaded iStat yesterday so I haven't had a reading when the flickering begins, but after an hour of playing WoW yesterday my CPU was 54, GPU heat sink 79, and ambient 17. I didn't get a reading on the power supply at the time but this morning after a bit of play it was at 73 when the GPU was at 75. All the while my fan speed remained solidly at 939/1100/998.

Doesn't seem right to me, but I know next to nothing.

The week number refers to the number of weeks in a year, so... week #1 could be 1st week of January and week #52 could be last week in December.

The Applecare Order to replace my 24" iMac (C2D) (with a new 27" iMac) was placed by Apple on 27th December 2009 (maybe thats week #52) Watching the status of my order progress - I noted that on 30th December ... the Order status changed from "Not Yet Shipped" to "Prepared for Shipping" which is also the live and current Order status... as I write this; (9:40am Saturday 2nd Jan 2010)
So... If my 27" iMac (C2D) were to actually ship sometime early next week (before Friday 8th Jan) I assume my unit could be regarded as either a Week #52 (assembly) or a Week #1 (shipped) depending on the focus of the beholder?

Are you sufficiently confused now.... on the absolute meaninglessness - of this label...?

Yes, but thanks anyway.

Quote/"Obviously ambient air temperature has a significant effect on fan speed. But that's not at the heart of the point I was trying to make in my "who-ha" post. I guess the going-in assumption around here is that the average Mac user has a double-digit IQ -- else we wouldn't need to have the effects of ambient air temperature on fan speed pointed out."Quote/

Well I guess it should be equally obvious that at lower ambient temps.... target and actual fans speeds will also be a variable - just as lubricant viscosity & bearing friction values all change when operating in different ambient conditions.... but you knew that, you being one of those double digits - eh?

Jon Abbott wrote:
Prior to the firmware update, I was able to play numerous movies (720p/1080p HD and non-HD) without causing flickering/blackouts... After applying the firmware update (which I just did on the 30th of Dec) I haven't had a chance to watch very many movies. "Stranger than Fiction" has caused flickering/blackouts 3 out of 3 times, and after watching nearly 2 hours of "Inglourious Basterds" it hasn't flickered at all. I'll keep trying "Stranger than Fiction" as well as other movies to see what happens.

So I just finished a couple other movies and they didn't cause any flickering/blackouts. I then played "Stranger than Fiction" again in the background and it didn't flicker either (it was mostly obscured with other applications though). The track record for flickering starting with other movies is 0%... while it is still 75% for "Stranger than Fiction"... I will keep playing it to see how repeatable the flicker starting is.

I received my 27" iMac core i5, Dec 28, 2009. An hour into setting it up and transferring files over, the display began flickering and blacking out for seconds at a time. A call to Apple, suggested installing a fix. I did so, and it seemed fine for a while. Today, I'm back here to check the forum for like anomalies because it started again. I am a more than a bit perturbed, having noticed this discussion began several months ago, and Apple is still shipping these units with defects. Will a firmware fix do it or is it a defective graphics/video card? I hesitate now to install my Adobe CS4 software which will bring more headaches if I have to return/exchange this... there are several forums going on this display topic.

NULCGI wrote:
Quote/"Obviously ambient air temperature has a significant effect on fan speed. But that's not at the heart of the point I was trying to make in my "who-ha" post. I guess the going-in assumption around here is that the average Mac user has a double-digit IQ -- else we wouldn't need to have the effects of ambient air temperature on fan speed pointed out."Quote/

Well I guess it should be equally obvious that at lower ambient temps.... target and actual fans speeds will also be a variable - just as lubricant viscosity & bearing friction values all change when operating in different ambient conditions.... but you knew that, you being one of those double digits - eh?

I have a B.S. and an M.S. in aerospace engineering, so don't try to be cute by attempting to dazzle me with big words like "lubricant viscosity" and "bearing friction." It ain't gonna work...nor are those properties in any way directly relevant to this discussion.

I'll try this again. The minimum posibble target fan speed, +regardless of ambient temperature+, is evidently established in the firmware. According to the Fan Control preference pane (my screenshot is published above), there is no way that the fan speeds can drop below 1200/1200/1000 RPM, regardless of ambient temperature. Put simply...in my iMac's case, it appears that ambient temperature is not a factor in determining the +minimum possible+ fan speed.

Now obviously there's a reason that Simon and cuenlain have lower fan speeds that do I. I don't know why that's the case. I would be concerned if I were cuenlain since it appears at first blush that his fans are not appropriately responding to changes in temperature. To contrast, I'm currently installing Windows Vista SP2 from within a VMware Fusion session and my CPU fan speed has jumped to 1700 RPM, yet my CPU temp remains a (relatively) cool 39˚C.

I have a B.S. and an M.S. in aerospace engineering, so don't try to be cute by attempting to dazzle me with big words like "lubricant viscosity" and "bearing friction." It ain't gonna work...nor are those properties in any way directly relevant to this discussion.

Who's Bullshitting whom here.....? Dunno which lucky bag you got those alleged credentials out of.... but if by chance authentic... you surely weren't there or listening - during the important stuff.

To even imply that Temp1 (ambient) when applied to Temp2 (subject) has no effect or relevance to control of Temp3 (environment) just demonstrates plain ignorance of the applied physics.
So, get off your academic pedestal pal, by your comments - you have proven yourself unworthy.

Let's assume 1/10 new machines is defective.

Then the chance of getting 3 bad ones in a row is pretty low. It must happen of course. If they sell a million machines then 1000 people will get 3 bad ones.

The odds are much higher than this however. Apple store policies may vary, but when you ship to Apple you get back a "refurb" machine. Since the main source of refurbs is flicker returns, and since Apple doesn't seem to know how to test for this, the odds of a refurb flickering is probably 1/2.

So the odds of 3 bad machines in a row is only 1/40 (1/101/21/2). So your experience is not too surprising.

This is why a mildly flickering machine should not be returned - the replacement may easily be worse. You should either request a refund or wait for a definitive repair.

If a machine is flickering badly it's worth a refund (if possible) or a return, but there's probably a 50% chance the replacement will also flicker.

Message was edited by: jfaughnan

I have a week 45 i5 machine that arrived either without an AirPort card or with a card that had become disconnected. Apple Genius verified the problem and ordered the part. When I picked it up they said the card was there all along but was not connected. So that was a hassle. That was on December 1-2.

Then yesterday, December 31, the flickering started. I installed the firmware patch and all was well for 24 hours, until a little bit ago. The flickering/blackout is now back. I will call in the morning and get an appointment to take it in, again.

I bought this machine from a mail order AAR, so I doubt the Apple Store is going to refund my money. Honestly, I am now so concerned about the all-in-one design I'd happily take a refund and upgrade to a Pro.

In the interest of completeness, the machine is otherwise great. There is absolutely no yellowing of the screen or dust beneath the screen. No whine in the drive.

Boys, come on now, no fighting : ) I hope my earlier posts ( when I was in a drunken stupor ) hasn't started a range war. My i7 must operate very differently than my old G5 Power Mac....and wish I never traded it in. I miss those fans reving like a ferrari.

My i7 fans according to istat are 941, 1099, 999. The funny thing is those values have fluctuated very little no matter what I do. I ran Geekbench and Cinebench multiple times while simultaneously playing a wicked game of chess, using iTunes with visualizer, and some other crazy stuff and my fans might have gone up 100 rpm. Funny thing there was only warm air coming from the top of the computer even though the CPU showed at 120, and HD was about the same. Even more funny is the ambient temp with istat shows 41 degrees. I know for a fact it's at least 55F in here ( hey I save a lot of money wearing a parka indoors during the winter : ) It would be nice to hear the fans rev a bit, but I may have to wait till Spring. I'm due to return this i7 soon as my new one from Apple should be here mid January. Funny thing is the horizontal banding I experienced when I first got the computer has never returned. This thing just purrs and it has a Seagate. I'm actually on the fence about giving this one back. I'm concerned the new one might not be as nice as this one.

NULCGI wrote:

I have a B.S. and an M.S. in aerospace engineering, so don't try to be cute by attempting to dazzle me with big words like "lubricant viscosity" and "bearing friction." It ain't gonna work...nor are those properties in any way directly relevant to this discussion.

Who's Bullshitting whom here.....? Dunno which lucky bag you got those alleged credentials out of.... but if by chance authentic... you surely weren't there or listening - during the important stuff.

To even imply that Temp1 (ambient) when applied to Temp2 (subject) has no effect or relevance to control of Temp3 (environment) just demonstrates plain ignorance of the applied physics.
So, get off your academic pedestal pal, by your comments - you have proven yourself unworthy.

C'mon man, don't be an a$$hole. I can guarantee that those credentials are authentic, and I think my employer feels I'm quite worthy. Besides, you started with the "lubricant viscosity" nonsense.

Of course ambient temperatures significantly affect the computer's internal component temperatures which thereby affect target and actual fan speeds. I'm not arguing that point. What I am saying is that it appears, at least in my case, that the +absolute minimum possible fan speeds+ are set by the firmware...an assertion borne out by the Fan Control preference pane. According to the temp vs. RPM graph, I could take my iMac to the South Pole, run it outside, and the minimum fan speeds will never drop below 1200/1200/1000 RPM. Based on the screen shot of the preference pane I posted above, how can you draw any other conclusion? I guess it's possible that the slowest possible fan speeds as shown in the Fan Control preference pane could drop based on ambient temperature, but then why wouldn't those minimum temperatures be shown in the first place?

Honestly, I think we're talking past one another, so we probably should just give up. I'm willing to concede the point -- the conclusions I've drawn were based solely on the apparent functionality of that preference pane, not any underlying physics.

Oh yeah, thanks for taking a personal shot at me though, I appreciate it.

Message was edited by: Schwa72