my macbook pro does not detect external display anymore

Same problem here, but with an interesting observation. I have a budget HDMI cable that manifests the problem when plugged into the HDMI slot.

1. Wake machine with HDMI cable plugged into HDMI slot... FAIL
2. Plug HDMI cable into Thunderbolt adapter; then plug adapter into Thunderbolt slot... IT WORKS
3. Unplug Thunderbolt adapter; then plug HDMI cable into the HDMI slot... IT WORKS (no reboot required)

Also, I tried the http://gfx.io/ solution without success.

Clearly this is a problem that Apple should address.

After inserting the mini display adapter to my MacBook Pro all the way in, I pull it out slightly.

And the display shows.

A while back I noticed that when I insert a memory card to the SD slot, I should leave some slack otherewise the card wouldn't be recognized.

Today I realized the mini display works that way too.

Try this:

1) Unplug monitor power and disconnect mini-display port from computer

2) Wait till power distinguishes on the externl monitor (even the standby light)

3) plug in the mini-display port first, then plug in the power for the adapter

As long as you don't unplug the mini-display port, the external monitor should always work now, even through Sleep and Shutdowns.

I can't take credit for this if it works for you. Found it on the fourms here a while back.

After a couple of years of no issues, I started having problems connecting my 2009 MacBook Pro to my LG external monitor (via mini/VGA). Tried a bunch of the suggestions made in this thread ... no luck. Then I came across this:

I hesitate to add to such a long thread but after weeks of frustration (and suffered ridicule when I could not use my Mac to support a presentation!!) I finally stumbled on a simple solution.

I had previously repaired permissions without apparrent success but I would recommend doing this as poart of good housekeeping anyway. Then I reset the PRAM. PRAM holds a number of system settings while your computer is switched off... including the display settings. To do this (copied from http://support.apple.com/kb/ht1379)

1. Shut down your Mac.
2. Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
3. Turn on the computer.
4. Press and hold the Command-Option-P-R keys before the gray screen appears.
5. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
6. Release the keys.

Worked for me first time.😀 I wonder why Apple could not have suggested that as a reply to the thread!! 😟

This worked for me. No idea how or why, or if it will continue to work, but just reporting on my experience. Hope it helps someone else!

After trying many ways,this worked for me, Thank you very much johnathanz. I could not understand and control the way my MBP, but it is OK now, although I must do many steps each time turn on my second monitor.

I want to add 1 more point, you must change output resolution matched with your second monitor when "arrange" tab display.

Thanks

I have another fix to try as well for anyone having an issue.

I seem to have an electrical polarisation going on as the HDMI Cable/DVI connector and the macbook power cable have to crossover at some point.

Attached is a pic of the ONLY way I can get the signal to make my SAMSUNG LT27 external monitor. If the power cable crosses at any other point across the connector or HDMI cable I get NO SIGNAL on the external monitor. Even a slight bump or movement and it's gone. It also has to be under in this exact position, if it passes over the top of the DVI/HDMI connector again I have nothing. I purchased new cables and connectors, zapped PRAM etc but this has been the only fix for me and is exactly the same with every one. The only similar thing with every combination was the power cable so I have to assume the sheathing/insulation in the cable that is supposed stop the emmission of electricity is of low quality

Just thought this might help some people as a different way to tackle it.

This is crazy, but it worked for me also! I had issues with my MBP Late 2011 detecting a Dell display via DVI-D link to Thundebolt cable. Once I did this method, plus changing the arrangement of displays in Display Preferences, I now can use my Dell monitor as a second display/desktop with OSX Maverick. Thanks for posting this!!!!!!!!

I have a Macbook Pro running 10.6.8, otherwise fully updated. I've been using my Sony Bravia tv as a display, having NO issues for months doing so.

I'm using a MiniDisplay Port to HDMI cord, and today its saying "Unsupported signal. Please check device output" I've restarted my MBP, unplugged my tv, restarted in safe mode, reset the PRAM, tried every HDMI port, tried multiple resolutions and nothing has helped.

My MBP isn't able to detect any displays and I am at a loss. The only thing I am thinking is to buy a new cord and hoping for the best. Any other suggestions?

Hi,

i have a macbook pro, 10.8.5, and i want to connect it to my Phillips Matchline TV (model 42PF9945)

I purchased a Thunderbolt mini display port to VGA lead, and have connected that from my thunderbolt port to the TV using a VGA cable.

Audio is connected too, from the mini jack of the macbook pro to the audio ins on the TV.

Problem is, when i turn the TV to 'VGA mode', it just comes up saying 'Picture format not availible'

Is there something i should be doing in Preferences/displays...?

Thanks for any help and advice

Hi,

i have a macbook pro, 10.8.5, and i want to connect it to my Phillips Matchline TV (model 42PF9945)

I purchased a Thunderbolt mini display port to VGA lead, and have connected that from my thunderbolt port to the TV using a VGA cable.

Audio is connected too, from the mini jack of the macbook pro to the audio ins on the TV.

Problem is, when i turn the TV to 'VGA mode', it just comes up saying 'Picture format not availible'

Is there something i should be doing in Preferences/displays...?

Thanks for any help and advice

Apple have started some years back to not care for their consumers its sad how many people have to go through this and still no real fix, just more crapply made computers from china made to break down. apple computer now break down just as much as PC's get viruses. I have 3 old mac's imac g4, mac pro g4, and imac g5 pre intel and still work with not problems after intel mac turned to crap.LOL!!!!! im trying to fix this same problem also

I had this problem about a year ago. I have a Macbook Pro 15 inch April 2010, 10.8.5, 2.4 Ghz Intel Core i5. I was trying to connect to a Samsung tv using a Dynex Mini DisplayPort to VGA adapter. After looking around, reading these posts, I finally decided that the adapter must be bad.

I was given a HP W2072a monitor, and because i had no other way to connect to it, i went ahead and purchased a new adapter, this time it was "Apple" brand. Same thing, Mini DisplayPort to VGA. I've had it for 6 months and it had worked great.

A week ago i unplugged the monitor from my computer, switched adaptors to a Thunderbolt to VGA adaptor and plugged it into my wifes laptop. She's running 10.6.8 and has a 2 GHz INtel core 2 Duo. Display works great. After she was done with the monitor i plugged the monitor back into my computer, and now nothing.

I have now purchased 2 almost identical adapotors, both do not work. I have tried every suggestion on this page. unplug, plug back in. repair permissions, resting the NVRAM, downloading gfxCardStatus, downloading SwitchResX, and even deleting the com.apple.windowserver.plist file in safe mode.

Nothing works, and after over 20 years of using apple computers, i'm ready to give it up.

Your description best describes my issue... did you find a solution?

I'm amazed that after hundreds of posts stretching back over 2 years Apple deems this problem of insufficient interst to fix. I have exactly the same problem. I just downloaded the new OS. No improvement.

i've tried the various fixes suggested. Used towork but no more.

Fortunately I havent ditched PC. I regret buying Mac.

Good luck everyone

After trying almost everything above, the following solved the problem for me:

1. Shut down macbook

2. hold down apple button + R

3. reinstall OSX

This will not delete your customized settings or files.

I got this tip by calling the apple support. I hope it will help you too!

Good luck!