irvbromberg

Oops, I didn't notice your paragraph "After a little while I noticed a really acrid, burning-electrical-insulation-type smell, which seemed to be coming from the MagSafe connector itself. This seems to have become ever so slightly discoloured, so I put it down to a short in the connector itself, and discontinued using it." So clearly something was burnt out. Nevertheless, would replacing the I/O board also solve the problem (at considerably higher cost) if dirt were present and the cause of a poor contact -- is a new female MagSafe connector present on the replacement I/O board?

No, I don't agree with any advice that suggests that there is a problem with the adapter nor with the laptop. First you need to consider the solution that I describe below: In my experience, the most common reason why an adapter with MagSafe connector fails to light / charge properly is because of dirt collected on the female (laptop) side of the connector, all along the inside corners of its rectangular outline. This dirt prevents the adapter's male connector from sitting properly and establishing and maintaining a good contact. Prove this by taking a suspected defective AC adapter and trying it on a new, clean laptop. It works right? The Apple Store "geniuses" do this all the time, without thinking through and realizing that the problem is dirt on the customer's own laptop! What's the solution? Use a magnifying glass to take a good close look at those inside corners of the female MagSafe receptacle on the laptop, and carefully clean out any dirt that is there. A sharp, thin instrument works best. It may...

USB-C also can handle much higher current and much faster data rate than Lightning.

Lightning plugs have all of their contacts exposed, and users inevitably touch them, depositing skin salts and oils that together with the electrical current over time causes corrosion of the plugs and the device’s internal contacts. USB-C ought to be much more reliable in the long term because users can’t casually touch any of the contacts. Lightning cables also have an extremely high failure rate at the point where the cable attaches to the connector, with broken conductors and/or insulators.

More specs on xeon W-2140B microprocessor:

https://en.wikichip.org/wiki/intel/xeon_...

The iPhone 7 is rated IP67. The difference between that and IP68 is undefined, up to the manufacturer, but immersion deeper than 1 metres, up to 3 metres.

In case anybody is wondering, "OIS" is an abbreviation for "Optical Image Stabilization".

The original iFixit guide described the step 4 screws as "tri-wing" but that is incorrect, it should say "tri-point" or "Y", and the required screwdriver diameter is 2 mm, not 5 mm. See this image:

http://en.wikipedia.org/wiki/List_of_scr...

The top row is tri-wing, the bottom row is tri-point, as found in this MacBook.

I also replaced the volume control buttons, specifically because the volume down button didn't work, but the problem persists even with the new volume control buttons and new cable assembly. I suspect that it's not a hardware problem, but I haven't found a software fix. Tried everything I could think of, even a full factory restore, still doesn't work. As a workaround I use the system setting that displays a moveable touch control that allows volume to be changed:

Settings --> General --> Accessibility --> AssistiveTouch --> On. This displays a finger-tip dot that you can move anywhere on screen. Touching the dot displays 6 icons, touch "Device" then there are more icons including "Volume Up" and "Volume Down", which do work. Of course this problem first appeared soon after my AppleCare expired.