yes it is for a sx-1050
The s/s relay is operated from the unregulated +76V, if it is failed, then it needs to be fixed.
R1 is open? or is it also just the thermal cutout?
Digikey has them, 317-1130-ND
Thermal Cutoff (TCO) 250V AC 10A 104°C (219°F) Axial
good luck