The design of these Schaffner mains filter units must be a bit suspect surely, the filtering should come into play only when the equipment is actually powered up, serves no purpose at all to have the mains filtered when the equipment is not in use?
The filter below has been removed from a Solartron 7150 Plus bench meter and inside the meter it is as if it rolled of the production line a few minutes ago, it really has not seen much use at all but these filters have.
So all the time that the meter sits with its power cord plugged in, even though the meter is switched off, the filter is ageing and is connected across the supply and so could equally let fly at any point day or night, what a crap design philosophy that is.
Once repaired, I'm leaved the rear mounted power switch in the on position and replacing the plug top for one with a switch built-in and use that to control the meter so at least the filter goes again, I'll be there and know about it.