If the '69 is like the '68s, the problem is possibly a burned out coil. When you open it you may see that the coil is fried. The clocks are mechanical and wound about once a minute by a closing of contacts putting 12v on the coil. Mine is on its 3rd or 4th coil in its 45 years.

If you decide to spend the money, the repair solution is sending it in to a place like The Clock Works http://www.clockwks.com for original parts or getting a quartz do-it-yourself conversion.

I believe the observable difference is the original mechanical second hand steps along each second where the quarz is said to move smoothly.