They are not worth repairing. Technology has passed them by. They are uncomfortable with the small sweaty vinyl earpads. They also have no bottom end whatsoever. They cannot play loudly.
Try one of the mid-priced Sennheisers, Beyers or AKG's. Even Sony makes a wide range of phones which are better than the mid-70's design origin electrets.
I have Sennheiser HD580's, Beyerdynamic DT990Pro's, Sennheiser 497's and the top rated by Stereophile JVC HA-D990's. They all smoke the electrets. You might still be able to find the JVC. It listed for 129.99 and is discounted. I think mine came from J&R Music World.
"If you can hear it, it's real".
Tom