Anyway, I came back here to mention that local friend G6OXW came round last week to borrow a plugin and extender board to use with his 182C mainframe which is a later version of the 180A because his baseline has been jumping up + down by a few dB
His original fault had been breakdown of the CRT heater winding on the mains tfmr which he resolved by hanging a modified toroidal tfmr on the back of the instrument. I haven't heard yet how he's progressing with the jumping (hint hint)