Monitor Displaying in Negative! Help please!

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New to Mac here.

I have a brand new iMac 21.5" running Snow Leopard. Everything is updated.

I also got a 2nd monitor for it on the same day.

The monitor is a 21.5" ACER (S220HQL).

I have plugged it into the Thunderbolt port on the iMac using a DVI cable into a mini display port connector.

I then click Detect Displays in system preferences> display

The monitor is picked up and they share the screen. I can move the mouse and items between the two.

However, the ACER monitor is showing everything in NEGATIVE! The monitor is fine as everything else shows up okay. But the image is reversing all the colours!

Any ideas, hints or tips? Or what I should try next?

Any help greatly appreciated
 

chscag

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It sounds like either a bad adapter or cable. Try substituting another adapter first as that's more likely to be defective than the cable.

The iMac Thunderbolt output (which you're using) is supposed to be backward compatible with the Mini Display Port connectors and adapters. There have been some reports of certain adapters not working right.
 

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Good advice. If the iMac's monitor is also showing a negative image check out the Seeing tab of the Universal Access preferene pane.
 
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Thanks guys!

I will try tonight. I think it might be a duff cable... as long as it's not the monitor!!! Or thunderbolt port!

Will feedback when I find out incase anyone else has the same problem!
 
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HI GUYS

Okay - a strange twist to the tale: If I do the universal access tip that was kindly given this happens: The 2nd monitor now goes the correct colours! Hurray! BUT the iMac (monitor) now goes into negative.

What have I learnt from this? The cable and adapter and monitor will display the correct colours. But the iMac isn't syncing properly. It seems one always has to be in negative!!!

Strange!

ANy more ideas?
 

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Fascinating. I don't think it's a sync issue - either the cable has some bits flipped or the Thunderbolt port on either the 2nd monitor or computer has something wrong - assuming there's no setting on the display that could account for this. Is there?

It might be worth a quick phone call to Apple's help line and see if there's anything in the knowledge base on this.
 

chscag

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Okay - a strange twist to the tale: If I do the universal access tip that was kindly given this happens: The 2nd monitor now goes the correct colours! Hurray! BUT the iMac (monitor) now goes into negative.

What have I learnt from this? The cable and adapter and monitor will display the correct colours. But the iMac isn't syncing properly. It seems one always has to be in negative!!!

It's not a matter of syncing. It still appears that either the adapter is defective or the cable. Universal Access controls your internal monitor; the adapter and cable are supposed to allow the correct signals to be sent to the external monitor. You can see from your experiment that the signals are being reversed.

If you change out the adapter and cable and still have the same problem, it's time to take the iMac to your local Apple store and have it checked out. It might be the Thunderbolt port itself that's bad.
 
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chscag

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Thanks for the video demo. Weird looking isn't it? As I said above, if it turns out that the adapter and cable are OK, the output port on the iMac may be defective.
 
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Could be.

I was wondering if anyone had any issues with Mini-Display running in their Thunderbolt port?
 

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There have been some issues reported. As was stated, not all mini display port adapters work right from a Thunderbolt port. I guess I should try mine on the new iMac but right now I have no need for an adapter.

And by the way, Apple's adapter for the Thunderbolt port is quite expensive.
 
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Thanks chasq

Hmmm... well i have it booked in at an apple store this weekend. Will have to see what happens... Thanks for all help so far
 

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Thanks dtravis. Alas the monitor does not take HDMI! :-(

I've reset the PRAM and the SMC... still nothing....

Looks like this is a no go situation at the mo! :-(
 

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Let us know what the Apple store folks say - I'm curious as to what it turns out to be.
 
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No worries, Brian. I will do :)
 
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Initial guesses turned out to be right: it was the DVI port cable. Didn't have a spare to test but genius bar did! All sorted! Thanks for help everyone!
 

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Excellent. Glad it's sorted. Thanks for letting us know.
 

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Initial guesses turned out to be right: it was the DVI port cable. Didn't have a spare to test but genius bar did! All sorted! Thanks for help everyone!

Ha! We never guess...... :p Anyway, we're glad you got it sorted out. Have fun and visit us often.
 
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I will do! Thanks once again guys, really appreciate it!
 

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