[Niechcial,Steve]

This was a new one on me. I was working on an HMV 1816 from 1952 which started making a loud intermittent clicking noise with a bright white spot on the picture. Pretty quickly, the clicks and spots became frequent and rapid, looking and sounding very much like the old car ignition interference on 405. Finally all was revealed when the valve holder for the frame o/p valve (ECL80) spectacularly burst into flame! Like most of the valve holders on this set, this one consisted of two pieces of paxolin rivetted together with the valve pins sandwiched between them. I presume the paxolin carbonised over time and eventually became conductive. Interestingly, the fire was on the inside, between the two layers, rather than on the outside. When you look at the outer sides there is not much sign of carbonisation. I attach two photos, but I don't think the effect shoes up very well. As I say, nearly all the valve holders fitted are of this type save the LOP valve and boost diode. They are probably the hottest running valves and they sit in more substantial plastic valve holders. I wonder if that is because HMV were aware of the limits with paxolin holders? I have known carbonisation of paxolin printed circuit boards cause many strange problems, but I've not seen it on free-standing valve holders. Replacing the valve holder was a real pain because as usual the pins were in a different relationship to the mounting holes. The set itself produces a lovely picture.