I posted this at /r/Bravia already. Maybe some ppl here have useful input as well. (link at end)
Hi, so I have a KDL-55W809c and there were some problems like breaking graphics etc. It was under warranty so I contacted the Sony service. The technician replaced the mainboard but now when I turn it on and go to information it shows an older model and less inches! KDL-43W805c. Have I been screwd over? I called the technician and he claims there is one mainboard for many different models and that it automatically tunes itself depending on the TV it is attached to, and that he had to come and manually change the model name in the service menu. Is this true or are they giving me an older model mainboard? Is there a way for me to find out? Thx guys!
https://www.reddit.com/r/bravia/comments/6p6w5s/wrong_model_after_technician_replaced_mainboard/
It's the same year's model - B at the end of the model number means 2015, C is 2016 and D is 2017. Having the same mainboard for different models is more than likely, as it's more cost effective to design and manufacture as few different boards as possible. I don't think there's any way for you to verify that it is indeed the same mainboard, but given the technician was able to change the displayed model from the service menu is good enough indicator for me that it's true and no one is lying to you.