Could you post a pic? Your description is a bit confusing. The yoke is not connected to the suction-cup thingumabob. Rather, it's the assembly that surrounds the neck of the crt (hence the term "yoke"). The HV feeds the crt through a recessed button in the bell of the crt, and the thick wire (usually red, but sometimes other colors, like black) from the cup connects to the high-voltage ("flyback") transformer on the analog board.
Take a look at the pics in http://68kmla.org/files/classicmac2.pdf to see how the HV lead terminates in a spring-loaded clip. That will give you an idea of the mechanical operation you need to perform to extract the wire (assuming that this is your problem).
If the Mac was powered up in the recent past, you will likely want to discharge the crt prior to poking about, otherwise you will become the discharge path. The shock will not harm you, but it can be most unpleasant. Instructions for discharging it are also in the linked-to doc.
Take a look at the pics in http://68kmla.org/files/classicmac2.pdf to see how the HV lead terminates in a spring-loaded clip. That will give you an idea of the mechanical operation you need to perform to extract the wire (assuming that this is your problem).
If the Mac was powered up in the recent past, you will likely want to discharge the crt prior to poking about, otherwise you will become the discharge path. The shock will not harm you, but it can be most unpleasant. Instructions for discharging it are also in the linked-to doc.