Hy Quad fans, I am the owner of a beautiful pair of ESL 988 since 2002, serial no. 988-0747 and 988-0748. lately one of them started to have a pop sound repeating aleatory each 1-4 seconds. That pop did not alter the overall sound but it seams to worn about some problems. It also seams that the sound came from the lower panel. A few month ago the same phenomena at the same lloudspeakerapiered to the upper bass panel, so I bought a new original panel and I changed it. Now I had just opened the loudspeaker cloth and grill as and it is the lower bass panel, in the dark, it glows intermittent. Unfortunately, during checking up for the fault panel, something unexpected happens...the other loudspeaker being disconnected from the amp but with power on, start doing a strange noise like an old radio interstation noise. I am somehow confused, so I'd like to send you a sample of that noise. Watch the attached file....what do you think about? It can be possible after 12 years, all the panels get aged..? That's why I insist to find not only the effect but the cause. Can be some fault from EHT or clamp circuit...? In any case I am listening at normal level, jazz and symphonic.....only vinyl with a small OTL 26W amp.