[robert1]

you have a problem that is very common to these Zenith radios. actually, there are two problems. the dial string wear is the result of the first problem. that is the tuning capacitor. what happens is that the grease that was used for the ball bearings on the front of the tuning capacitor has dried out, causing the shaft to be stiff to turn. what happens is that because of the extra resistance, the dial cord is stressed & with the additional stress, it stretches. it also loses it's gripping properties. fortunately, Zenith used a separate string from the tuning shaft to the tuning control & used a separate string for the dial & pointer.

to make things simpler, try lubricating the AM tuning condenser at the front where the ball bearings are & manually work the tuner by turning the pully's on the front of the tuner by hand, back and forth until it loosens up. you also should apply a thin coat of lithium grease across the edge where the dial pointer travels. that helps a lot.

when you go to lubricate the tuning condenser, what you need to do is turn the pulley to where the plates mesh with the other plates, attach a nozzle extention to a can of WD40 (or equivalent degreaser), spray directly into the opening where the ball bearings are, then apply lithium grease around the ball bearings. DO NOT get any spray into the tuning plates.

after doing the above, you may not need to replace the dial string.