I own Quad 2905's and I had to make repairs. Other than listening to them to see if they sizzle, pop or sound distorted in general, you'll have to take them apart. Two main things to consider are burns in the material or board separations from broken glue joints.
Martin Logan electrostatic speakers, How do you know if the panels are good?
I'm considering some older, Summit speakers. I'm reading a bit about the panels going bad and being expensive to replace. How do I know if they do?
What do I need to look out for with the panels or other parts? Anyone mind enlightening me?