Sheldon D. Stokes published an article about 6 years ago on how to rebuild the Quad ESL's. It appeared in a magazine called "Positive Feedback". Many of his designs have been published there. He has an excellent site on - among a lot of other audio stuff - refurbishing the Quad ESL 55. If you don't feel up to rebuilding the ESL 55 yourself Sheldon D. Stokes can do it for you at very reasonable prices. He allowed us to publish parts of his work on our site. You can find the links below.
ESL 1.0 "Ever since I started rebuilding Quad ESL's I wanted to try to build my own ESL's".