Apple shitty iMac PSU design? - Page 1
Forum section: electronics / repair

author: isopropilick
author_rank: Contributor
timestamp: October 05, 2015, 01:51:04 am
content: The particular model is: iMac A1419 Late 2012 27"My current work includes repair computer parts. It is the third occasion that appears the same model with the same problem !!!The records of the "no-break" show only a peak of 240 VAC is incredible that a jump of voltage (120VAC to 240VAC) cause the explosion of an SMD Ic.It is a matter of poor design or intentional failure to bring visits for service?I leave some photos of the damage below. And some of the specifications and input power supply.(Without wishing to offend fans of apple)

author: fivefish
author_rank: Frequent Contributor
timestamp: October 05, 2015, 02:52:37 am
content: So are you saying this problem happens when plugged into a 220V outlet? Is Mexico 220 or 110V?

author: isopropilick
author_rank: Contributor
timestamp: October 05, 2015, 02:55:35 am
content: Quote from: fivefish on October 05, 2015, 02:52:37 amIn Mexico the main is 120V but the psu is rated 100 - 240.And the problem was 235.8v (max) in the input.

author: BradC
author_rank: Super Contributor
timestamp: October 05, 2015, 03:07:43 am
content: My Mac has the same PSU in it and sees regular runs up to 249v with intermittent spikes in excess of 260, so I don't think that is the issue.Our mains is rated at 240 but we're mostly above 245 and in summer with the mass of solar installations surrounding us we often see peaks north of 255 and up to 260 as cloud banks move around.It's not as bad as it was. 2 years ago we saw 270 a couple of times which blew a lot of incandescent lamp filaments, but the power supplier has managed to bring that mostly under control.None of our switch mode supplies failed under these conditions however.

author: isopropilick
author_rank: Contributor
timestamp: October 05, 2015, 04:39:35 am
content: Quote from: BradC on October 05, 2015, 03:07:43 amCan be a consequence of fast switching? 120v to 0v to 240v to 120v fastest than a relay can change the state?

author: zapta
author_rank: Super Contributor
timestamp: October 05, 2015, 05:15:09 am
content: Quote from: isopropilick on October 05, 2015, 01:51:04 amAren't you happy that you have a job and that you are getting better in diagnosing this repeat problem?

author: BradC
author_rank: Super Contributor
timestamp: October 05, 2015, 10:49:49 am
content: Quote from: isopropilick on October 05, 2015, 04:39:35 amI doubt it otherwise they'd be blowing up when people plugged them in.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 05, 2015, 11:59:52 am
content: What is the chip?What side is it connected to (mains or low voltage)?Tim

author: tooki
author_rank: Super Contributor
timestamp: October 06, 2015, 09:34:54 am
content: Quote from: isopropilick on October 05, 2015, 01:51:04 amThree units of the most popular desktop computers in the world! Stop the presses!Anyway, with how closely I follow Mac tech sites, if this were a widespread problem, it would be widely discussed there by now, and it's not. So I would assume it's a local environmental factor rather than a broad design or manufacturing flaw. (Apple has been using Delta Electronics power supplies for decades, and they have a reputation for being unusually robust.)Quote from: isopropilick on October 05, 2015, 01:51:04 amNope, you just immediately included insinuations of deliberate sabotage by the manufacturer to cause service calls. No way anyone could be offended...Never mind that it'd be illogical for a company to design products to failwithin warranty. (AppleCare is for 3 years from date of sale, so most "Late 2012" units would still be covered by AppleCare right now.) But of course, despite what the conspiracy theory tinfoil-hat anti-corporate crowd claims, nobody actually designs products to fail on purpose. They merely design them to be as cheap as possiblewithout failing during the warranty period, which isn't the same thing. In any event, Apple products are known for having above-average build quality and hardware longevity, so the argument of deliberate sabotage is a non-starter.Quote from: isopropilick on October 05, 2015, 04:39:35 amErm, that's not how switch mode power supplies work. The input voltage range is just that: a continuous range, not a bunch of discrete ranges. (In fact, many SMPS's can work on lower voltages than stated, and on wider ranges of frequencies, often down to DC!)