Macbook air thunderbolt problems

When I connect my Macbook to my TV via the thunderbolt cable to HDMI3 the Macbook recognises the TV but the TV says there is no signal (same result with HDMI1 and 2).

It has worked in the past, though didn't work yesterday when I tried a different TV.

HDMI3 works fine with the pvr and dvd player.

No problem with using Google Chromecast to cast to the TV.

I am using OS X El Capitan ver 10.11.6 (15G18013)

MacBook Air (13-inch, Early 2014)

In my ignorance this seems to point to a problem with the laptop (I have renewed the cable), is it repairable or is it too expensive to bother ?

Does this thread help re scaling post?

https://forums.macrumors.com/threads/thunderbolt-hdmi-samsung-tv-not-recognized.1960085/

Cheers swarfendor but the mac recognises the TV but the TV says no signal. I had tried the suggestions on that mac forum but no success. I actually had Samsung repair the TV a couple of months ago when the problem first stated and it worked for a couple of weeks but has again stopped. Mac doesn't work on other TV's so possibly the El Capitan update is the problem.

I suspect it also depends on which version of El Capitan reading this post:

https://origin-discussions-us.apple.com/thread/7549390?start=0&tstart=0

Does the trouble shooting guide help at all?

https://support.apple.com/en-us/HT201177

Could this be a possible solution for you?:

http://www.redmondpie.com/how-to-airplay-mirror-mac-to-samsung-smart-tv-without-apple-tv/

Cheers Swarfendor again. I'll try the third suggestion tomorrow, have tried the others with no success.