Assuming its a 13GC10 or later HC, JC, KC, LC..........
Remove two 1/4" screws in top corners of chassis. There may also
be also one or two along the sides. Now the chassis will tilt down.
The can is behind on the sub-chassis. MOST were mounted on
a small steel plate held by a 1/4" to the steel sub-chassis. Remove the
bolt & it flips out and its easy to change. If you need more room pull the
four 1/4" under the set & the chassis will come out. Take your time
so you dont damage the CRT board or pull any wires. At that point
everything unplugs if needed. Zenith always put serviceability on top.
The only mistakes I remember were the dial lamps & cans in the
hybrid sets. They actually took a few minutes to change !
73 Zeno
LFOD !