There are 2 select buttons, one on the CRT and one on the carraige.
I am going to step out on a limb here and assume it is the one on the carraige.
There are 2 possibilities. Both mean you have a short to ground and thus blow the fuse.
There is a cable that runs from the control through the flexible wire way to the carraige. The cable may be damaged. Yes it is a chore to get to it and repair it or replace it.
Second possibility is that the switch box on the carraige has a plug on the back that coolant gets into. The wires can corrode and break off thus also creating a short. Take a look.