I bought a pair of Janszen Z-600 speakers a few years ago at a thrift store for 20 bucks and they worked great. They have a 10" woofer and 2 electrostatic panels for the highs. I have used them off and on since I bought them but recently it seems that the high frequencies have dropped quite a bit. Could this be a power supply issue? If so, is the power supply a difficult rebuild? I have moderate experience recapping tube amps and stuff like that, but that is about the most I have done. Any help or suggestions would be greatly appreciated.