Prewar model K transformer service?

I have a Model K 150 watt transformer.  The power cord is badly cracked and the number 4 variable voltage port is dead.  Other variable voltage ports and all the fixed voltage posts are working and supply correct voltage.  Are these units serviceable?  I don't see any obvious way to open it up to replace the cord and solder connection to the dead variable port myself.  Any recommendations for a service center that can do the job?

Thanks.