MacBook – wrong scaling for external HD monitor using VGA, MBP 13″

displaymacbook proresolutionvga-adapter

I know this sounds similar to other questions but bear with me – I've investigated and am not finding any solutions. Sorry in advance for a lengthy question.

I have a MacBook Pro (13-inch, 2016, Two Thunderbolt 3 ports.) Since I purchased it in summer 2016 I've used it with a couple of different cheap HD monitors by Samsung, connected with the Apple thunderbolt-VGA multi-adapter. This has never been an issue.

A few days ago, I cracked the screen. (That's another story.) I'm a developer and have to keep using this machine heavily for the moment (My backup 2012 iMac would have a hard time keeping up with the current tasks.) It continued to work just fine in "clamshell" mode with an external mouse and keyboard.

This evening though, I opened the MBP lid to see if I could access its camera. Suddenly, the external display resolution defaulted to 800×600. The "scaled" options in Display preferences now allow for 800×600 and 1280×1024 only.

Only by option-clicking the "scaled" radio button in Display preferences can I access the monitor's native resolution of 1920×1080 (this has never been necessary before.)

(and now the meat of the question:) When I do select the full HD resolution, the image is almost correct, but asymmetrically narrowed – leaving a black bar of, I don't know, maybe 120px on the left side and 40px on the right. It's almost usable, but causes a definite headache.

Moreover, the exact same problem occurs with a different monitor! It certainly seems like a software/firmware issue on the MBP itself.

Has anyone else experienced this?
Could it be somehow due to the cracked Retina display? (If so, how??)

Things I've tried:

  • resetting the SMC

  • resetting the PRAM

  • disconnecting all peripherals besides the VGA adapter

Things I haven't tried:

  • booting into safe mode (I'm worried I'll be stuck not seeing anything at all on the external display.)

  • using an HDMI adapter (I never bought one for this machine.)

  • swapping the VGA cable (will do)

I'm a bit at a loss and would appreciate any ideas or reports of similar behavior!

Best Answer

ok, replacing the VGA cable worked.

and - apologies - it appears to be the same issue/solution reported here: External monitor randomly lowers resolution adds black borders

and here: External monitor viewport appear shrunk in native resolution on MBP

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