[Gem930]

I tried the search function on this but (as usual) I could not get the answer. 
I have almost no hot water out of my shower valve. From the amount of crap I have pulled out of my screens. In other faucets its likely the screen is  plugged. I cannot figure out how to get the temperature control knob off. There is no removable cap on the front of the knob to conceal a set screw. Does anybody know how to get this thing apart?  Additional info:  Hot water in all other faucets works great so I doubt it’s the mixing valve at the aqua hot.  Thank you.