Wednesday, May 28, 2008

Reset resolution of LCD TV Display connected to a Mac

Previously, I have encountered a problem where the resolution was set wrongly on a Mac mini, which resulted in a "Mode not supported" error that appeared on a Samsung LCD TV.

The problem with this error is that the Mac is too smart. It recognises each monitor that you have connected to the Mac. Therefore, if you connect a normal LCD monitor, and a LCD TV, it will save individual display settings for both the devices. Its not a simple case of just plugging in another monitor and resetting the resolution.

First... The steps that do not work:
  1. Resetting PRAM
  2. Safe Boot
  3. Removing

Tried all of it, and none works in resetting the resolution! :(

After some days of tinkering, I've managed to reset the resolution on the LCD TV using the following steps which I've found through trial and error:
  1. Connect an external monitor to the Mac and ensure that System Preferences > Sharing > Remote Management is turned on
  2. Ensure that System Preferences > Security > Firewall is either set to Allow all incoming connections or Set access for specific services and applications. If it is the later, remember to ensure that Remote Management is enabled.
  3. Reconnect the "locked" Mac to the LCD TV
  4. Use another Mac Mini, or MacBook and connect the 2 computers with a ethernet cable.
  5. Look at the Finder of the other Mac. You should see your "locked" Mac. Click on it, and click on Share Screen (Alternatively, use any VNC client)
  6. Click on System Preferences > Displays in the Share Screen/VNC window and reset the resolution.

That is it... Using this method, I've managed to reset the resolution of the Mac so that it works on the LCD TV. I only tried this on Leopard macs, but theoretically speaking, this should work on a Tiger too, with some minor adjustment to the steps.

Remember... Never play with the resolution if you do not know the supported modes. It was quite painful for me to figure out how to reset the resolution.


Anonymous said...

Thank you so much for this. I had this common issue with the mac giving too high refresh rate. This solution is perfect, easy to do and helped me justify buying both a macbok and a mac mini.

chantc said...

Glad that someone actually understood what I was trying to convey.

Sometimes, the computer should not be too smart. :)

allenbina said...

smart, but i only have one mac :(

chantc said...

Sorry to hear that. I haven't heard of a way to resolve this without a second mac though.

Chris said...

I really appreciate your post, as it finally allowed me to solve my own "Mode Not Supported" problem with my Samsung TV. Using the remote management was the only way I was able to resolve it and your blog post is the only place I ever found the suggestion.

I made a post of my own ( that details a slightly different method that people can use.

And to "allenbina": it's far too late, I'm sure, but if you use the network method I mention in my post, I'm pretty sure you can connect via VNC with any computer (i.e. Windows, Linux, etc.) using a standard VNC client, not just by using a mac.

Anonymous said...

Thank you! No one at the Apple store could figure it out, worked perfectly!

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