You may be remembering the chassis tube location diagrams that were glued inside the cabinets of most sets. Very handy since many tubes required some physical contortion on the tech's part just to reach them in an inaccessible part of the cabinet (when in the customers home). Also they gave the tube type (6AU6, 6V6, ect) by which you could locate and swap the tubes you suspected of causing the problem.
Further a schematic *glued* inside a cabinet would be of little use in the shop since after removing the chassis it was put on the bench to work on and the cabinet was stored in the back of the shop.
But I can only speak for my 50's experience. Your 70's experience may very well be a YMMV.
As an aside I occasionally lost some skin when trying to reach an inaccessible tube and getting my arm too close to the picture tube's high voltage wire. Getting zapped was uncomfortable, but worse it caused my arm to involuntarily jerk back and often (with my luck) it connected with a sharp protrusion of the chassis on the way out.
In the middle 60s I worked testing newly manufactured GE mainframes. You would have thought board testing would have caught all board problems but often when a machine had a problem it was caused by a (new) bad board. So board swapping was a still valid troubleshooting method even when testing at the new system level.