Second monitor stopped working randomly

Question

Level 1

34 points

Second monitor stopped working randomly

iMac late 2013, 27". Running Sierra 10.12.2 - Second monitor: Dell S2240M

I've had this monitor hooked to the computer for 2 years, via a Thunderbolt to DVI cable. It has worked fine for that time. 2 days ago, no system changes were made, went to wake computer up from display sleep to use it, the second monitor would not wake up.. it appears it is no longer receiving any signal. I swapped out the monitor, and the cable, for another, same problem.

I tried resetting PRam (press and hold option command PR on boot ding, hold until it reboots again) and SMC (at least I think i did? by press and hold shift control option while depressing power button,... also tried unplug power, hold power for 5 seconds, plug power back in, boot up).... and it is still not working. Also, it appears the Imac is still detecting the display fine. Any help appreciated to troubleshoot it??

iMac (27-inch, Late 2013), macOS Sierra (10.12.2), null

Posted on Aug 8, 2017 10:22 AM

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Answer 1

den.thed

Level 10

91,306 points

Aug 8, 2017 11:07 AM in response to illbilly

Any reason why your hanging back on 10.12.2 Those earlier versions tended to be less refined and buggier.

Does the external monitor work in Safe Mode?

Use safe mode to isolate issues with your Mac - Apple Support

Personally I would suggest installing the latest 10.12.6 Combo Update over the top of whatever version your on.

Download macOS Sierra 10.12.6 Combo Update

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Answer 2

den.thed

Level 10

91,306 points

Aug 8, 2017 2:03 PM in response to illbilly

Hmm... try resetting the SMC again.

Reset the System Management Controller (SMC) on your Mac - Apple Support

Only this time, disconnect everything from the iMac and let it sit for a minute instead of 15 seconds.

Then reconnect everything including the external monitor and startup with a NVRAM reset.

How to reset NVRAM on your Mac - Apple Support

Only this time, hold the Option Command P R keys until you hear it chime the third time.

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Answer 3

rkaufmann87

Level 10

148,488 points

Aug 8, 2017 11:05 AM in response to illbilly

When you reset the SMC, did you disconnect the cable from the back of the computer or the power source? Correct procedure is from the back of the computer.

Also, when doing SMC and PRAM resets it is wise to do them with ALL peripherals disconnected.

I also agree, you should keep Mac OS up-to-date.

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Answer 4

illbilly Author

Level 1

34 points

Aug 8, 2017 1:50 PM in response to den.thed

I had an issue updating Sierra a month back so left it as was. I went ahead and updated now with all the updates in the App Store, now at 10.12.6. No signal. (I assume going to 10.12.6 through the App Store, has the same effect as downloading the Combo update separately).

Booted into Safe mode. No signal.

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Answer 5

den.thed

Level 10

91,306 points

Aug 8, 2017 2:11 PM in response to illbilly

Sounds like the port overload protection is tripped.

If you follow the steps that I just posted at 2:03 PM it should reset the port overloads.

If not, then you will need to schedule a service appointment for your iMac.

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Answer 6

illbilly Author

Level 1

34 points

Aug 8, 2017 2:18 PM in response to den.thed

Hmmmm... Gonna try your instructions again later after leaving it off for a while and see if that changes anything.

Yeah called repair shop just now.. Of course being a 2013 its out of applecare..... so a New Logic board is $700.... plus $200-300 in labor...

Had a 2010 Imac that the USB ports randomly stopped working in 2013... went ahead and repaired for about $1000 then. And the computer still was acting weird, so I ended up getting this one... looks like my three year cycle is complete again....Unfortunately, I wont be wasting $1000 to repair this one.

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Answer 7

den.thed

Level 10

91,306 points

Aug 8, 2017 2:36 PM in response to illbilly

You may just have a bad device, cable or adapter somewhere in the mix that is shorting or overloading the ports. Do those resets and then test your devices, cables and adapters one at a time until you can isolate which one is causing the problem.

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Answer 8

illbilly Author

Level 1

34 points

Aug 8, 2017 1:54 PM in response to rkaufmann87

Just shut down, unplugged every cable from the back of the computer. Waited 15 seconds+, plugged them back in, waited 5 seconds+, then booted. No signal.

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