Hello, as attached schematic. I'm trying to repair a Acer AL1716 power supply board with 12V rail output only 8V. After some investigate, I found TVS diode code P6KE9.1A (ZD153) is shorted (measured and got 2 ohm). From what I understand, normally TVS would use to clamping between positive and ground rail for surge protection but in this power supply it just clamping between 12V and 5V output. Is it got special purpose? What is behind this design or it's nothing special at all?
Also, since I can't find replacement parts here, closet part is P6KE20A which quite large different voltage rating. What can I do with it, Leave it open? or P6KE20A would be fine?