I have this set in the shop. The set will not
power up. The error code is 6 blinks, which is B+ 5v line overload or
short. I have checked IC504 and it checks good out of circuit. I have
replaced C530 and C540. I have removed the B and M boards and still the
5v will not come up. I have the 7v unreg. It is measuring at 7.63v on
the meter. I am missing the 5v unreg, and have changed C6593. I can not
find the 5v and I am afraid I have made this harder than it should be.
Any suggestions? 
