[Phil Coffman]

Our church acquired an MCS-8M and had the same issue when connecting MBP or an iMac.

This device fixed it: https://www.amazon.com/Gefen-EXT-HDMI-EDIDP-HDmi-Detective-Plus/dp/B001RIMZUW/ref=cm_cr_pr_pb_t

Looks like there’s an EDID issue between the switcher and the imac but this has totally solved it for us.

Thanks to Rommie Sebo for his post here:
https://forums.creativecow.net/thread/158/857573

Thought I’d quote the part that was helpful:

“Ben,I recently purchased the Sony MCS-8M HD/SD Multi-format 8 input video switcher. Here is a breakdown of all the inputs; 4 HD-SDI, 3 HDMI, and 1 DVI. It has 2 DVI outs (1 for a multi viewer display) and 4 HD-SDI. We use Playback Pro Plus on a Macbook Pro for our video playback and Powerpoint slideshows. The only issue I had was trying to run a signal out of the laptop (Macbook Pro with thunderbolt port) into the switcher. The laptop has HDCP so it will block the signal out for protection purposes but we found a work around. We put a Gefen DVI Detective inline between the Macbook Pro and the Sony switcher. Now the switcher has no problem seeing the Macbook Pro laptop. Note; sending an HDMI signal into one of the switcher’s HDMI inputs would require Gefen’s HDMI Detective as well. Hope this helps.”

Phil