Hi, I have an A4000T Mediator with a Radeon card which has both VGA and DVD outputs. For some reason it doesn't display on a VGA CRT. I have the appropriate adapters on my MacMini that could connect the DVI output to my HDTV via an HDMI port, but there are also "Ultra HD" monitors at Costco for as low as $129.

An Amiga hardware-knowledgeable friend cautioned that the UHD monitor (3840 x 2160 resolution) may not accept the Radeon's output (and thus cause damage).

What's your opinion?

Hi, I have an A4000T Mediator with a Radeon card which has both VGA and DVD outputs. For some reason it doesn't display on a VGA CRT. I have the appropriate adapters on my MacMini that could connect the DVI output to my HDTV via an HDMI port, but there are also "Ultra HD" monitors at Costco for as low as $129.

An Amiga hardware-knowledgeable friend cautioned that the UHD monitor (3840 x 2160 resolution) may not accept the Radeon's output (and thus cause damage).

What's your opinion?

No opinion but your friend is crazy if he thinks it will do damage.  

Yes there may be an issue that whatever screenmode you are using might not be supported by the monitor you are hooking up.  In any case, 99% of all HDMI or DVI monitors will accept 1280x720 which you can use with the Radeon.  The odd Amiga resolutions might not be supported but most of the time will work at 640x480 or 720x480.  VGA type resolutions like 800x600 are less likely to work but you won't really know until you try it.  The few UHD TVs I've tried support lower resolutions as well.  Start off by setting up a 1280x720@60Hz or 50Hz screenmode and go from there.