I've found a forum with much better information on how to replace the IC. Unfortunately, it is in German and very long:

https://www-mikrocontroller-net.translat...

On the upside, it looks like there's a simpler fix than replacing the MXT chip if you do not feel confident with SMD soldering. One can use a small D-SUN brand voltage regulator. The forum has pictures of how it is wired in. Look for the posts by @goaty as those are by far the most helpful.

Sounds like Step 8 is too vague. Would it help if I changed the guide to say "unsolder the old chip and solder in the replacement"?

Or is the problem that this guide should have made it more clear that it at the outset that it requires being able to solder?

Or is it that soldering surface mount components like this is not adequately illustrated? Hopefully someone (maybe you?) will photograph that process to make it more clear.

@fex42 Thanks! I'll see if there's a way to incorporate your fix into the guide as an alternate path to follow.

Hi @goaty , can you comment on the suggestion from @fex42 about using an MP1584EN chip? On paper, it looks to be a better chip with higher max ratings (3 vs 2 A, 1.5 vs 1 MHz, 28 vs 20 V). fex42 also said piggybacking the chip was simpler than removing the old one, but they were vague about how it got wired up. I cannot find the MXT2410SX datasheet so I do not know if this is supposed to be a pin-compatible replacement.

On Dec 8, 2024 @fex42 wrote:

Instead of repairing the defective 5V control circuit, I simply piggybacked a small switching regulator on top with thick double-sided tape. By removing the coil, the output of the defective original regulator is separated from the rest of the circuit and you have a nice contact on the board to feed in the 5V. This is not only much easier than replacing the chip (which I also have done successfully some years ago) but these small DC-DC buck converters with MP1584EN chip are simpler to source than the original MXT2410SX chip and also cheap.

Nice idea, fex42! Did you take photos of the process? It would be good to update the guide with your simpler piggyback method.

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I can't find the datasheet for the original MXT2410SX chip, so I'm not even sure what "pin compatible" looks like or why removing the coil disconnects the defective chip. Can you explain a little more?

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It looks like Monolithic will be discontinuing the MP1584EN. Would the MP2410GJE or MP2338 work? I notice that the 1584 seems to have much better specs (higher current, voltage, and switching speed), but it'd be good to give people options if it starts becoming hard to find.

(Update: I believe Apple's wording was incorrect. "Top" is closest to the stand, not the display, because those are the slots which had the SO-DIMMs in the iMac I just checked.)

It does make a difference, but only if you have a single stick of memory. Here's what Apple says about the 27" 2011 iMac:

"i5 and i7 Quad Core iMac computers come with both top memory slots populated. These computers will not start up if only a single DIMM is installed in any bottom slot; these computers should operate normally with a single DIMM installed in any top slot.

Core Duo iMac computers should operate normally with a single DIMM installed in any slot, top or bottom. ("Top" and "bottom" slots refer to the orientation of the slots in the pictures below. "Top" refers to the slots closest to the display; "bottom" refers to the slots closest to the stand.)"

Source: https://support.apple.com/en-us/108317#2

Amusingly, although Apple defines "bottom" as being closer to the stand, that is opposite to the orientation of the pictures.

Apple does not mention memory channels in their text or diagrams. Since they came with both top slots populated, a good bet is that they are on separate channels (left and right).

Nice tip, Clinton! I’ll have to try that next time. Do you have photos of how it is done so this guide can be updated?

Two screws need to be removed. Before lifting, slide the base cover slightly towards the battery to release it.

P.s. this isn't as important, but where did you hear the tip about the hairdryer? I'd leave that out as firmly peeling it up works fine.