I have an old Merlin 410 PBX in my house, acquired dumpster diving when a local volunteer Fire Department upgraded their PBX. It is on a UPS, has the music on hold feature, with 3 incoming lines from my telco. Since summer, after some thunderstorms, I've noticed significant white noise in the background on all extensions. No noise if I use the same outside lines without the PBX. Is there a specific area / module of this PBX that is known to fry during thunder storms ?
Thanks Steve N2UBP