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A2115 / 2019 / Processors from 3.0 GHz 6-core i5, up to 3.6 GHz 8-core i9. Released March 19, 2019.

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ZERO POWER after NVMe + SATA SSD + CPU upgrade


I’ve just followed along with this video, using OWC’s kit, to replace my Fusion drive (small, old NVMe SSD + 2TB HDD), with a 2TB OWC NVMe, and a SATA SSD.

I also upgraded the Core i5 CPU to a 9900K Core i9, as per various threads here, and videos on YouTube.

I had no issues with the tear-down (screen is intact!), no issues with the replacement of the parts, and reassembly. The only thing I have ‘not done’ is peeled off the second side of the tape around the edges of the chassis/screen to re-affix them together - in case I needed to go back inside - ie ‘problems’.

So, I know of no issues, but have plugged it in, hit the power button and… nothing.

Not a beep, no flicker of anything on the screen, no fan-noise, etc.

I am not aware that iMac have any sort of power fail-safe mechanism, if the screen is not back in full-contact with the chassis (ie ‘because I’ve left the double-sided tape unpeeled, as yet), as a ‘cause’ for this zero-power state?

Prior to doing this exercise, I created a time-machine backup, and two clones of the macOS volume on the Fusion Drive, on two different external drives, one using Carbon Copy Cloner, the other Superduper - but obviously with ‘NO’ power, I am not in a position to run Recovery Console etc.

I have no power! I read various options for ‘de-fusion ink’ the Fusion Drive prior to dismantling the machine and making the changes, but most accounts suggested that if you are replacing both of the physical drives the previous Fusion Drive was comprised of, there is no need to do this.

I’ve checked my power cord and socket - there are other devices powering fine from the socket. I have plugged in the magic keyboard via Lightening / USB, and a wired mouse just to see if that would offer any change of state - no.

Even if there was something incompatible or badly ‘seated’ about either drive or the CPU (and 128GB RAM - which was working fine previously), I think I would expect some ‘show of a POST screen’, or ‘motherboard beeps’ or some other indication of power - OR, am I making an assumption here?

It is like I have not reconnected the power-module to the motherboard, or the power-on button to the motherboard correctly, but I am pretty sure this is not the case - hardly the most tricky of the reconnections that needed to be made!

I also cannot believe the machine to be so quiet that it’s ‘on, but there’s a issue with the screen’..?

Otherwise, I don’t know if there is a ‘flush’ of memory settings etc that I can action, or some other low-level ‘hardware reset’ I can impose on the machine?

I am not aware that this is ‘too many hardware changes’ at once to be ‘acceptable to Apple’ (!), or whether the 9900k i9 is somehow incompatible - but there are whole threads about CPU upgrades and/or ‘complete upgrades’ done by others, which seem to make its clear that the changes I’ve made should be all-good.

Again, I’d at least expect some sort of indication of an error, even were the CPU a dud, or whatever - nothing.

Help, if you can..!

Many thanks, Damian

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Well I think your issue is the mounting of the CPU, I often see people struggle with the heavy spring power as well as tightening the mount correctly. Lastly, some often put too much Thermal Paste on so it spills over the side of the heat spreader wetting the green carrier board and the SMD devices mounted on it which then messes up the signals.

So you'll need to go back in and pull the CPU out clean off any paste off of the green carrier and the SMD devices, you may need to use loadable spray can like this Reusable Refillable Multipurpose Aerosol Compressed Air Spray Bottle for Cleaning and Lubrication which is what I use with the pinpoint tube to fully clean around the SMD devices using 90% isopropyl alcohol or other needed solvent. The board needs to be spotless of thermal paste.

Next inspect the chip socket for damaged pins, being very careful not to snap off the pin. Last step is how you put the CPU in and the plate and springs, then tighten the mount screws.

Its' a very tight fit with the RAM cowling just above it. I find having a second set of hands to hold things helps. I made a jig out of wood which helps me. The screws need to be just barely finger tight, then you want to use the same method you use for tightening lug nuts for a car rim jumping for side to side so you are evenly tightening the screws down. Once you get the board mounted back in the case use an external monitor to see if the CPU is properly mounted before you put the SATA drive back in (just the blade drive alone).

That should do it.

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Hi Dan. So absolutely no ‘POST’ action expected, no motherboard beeps, nothing to give any insights? ie the excessive paste/mis-seated CPU will result in this ‘NOTHING’ state? Have to say, if the CPU is mis-seated, It will be damaged, given the spring-plate/degree of pressure that mount creates!

I’m hoping I just haven’t connected the power board to the m/board fully, or something a bit easier… but I might have to consider swapping the original CPU back in, with the new SSDs, and see what happens there.


@doctorcloudbase - Yes! No/bad CPU - No sound source via the systems EFI firmware Bong sound file it has.


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