[sdiy] thermal antagonists

[Paul Perry]

Mark, you could test whether it was a solder problem or a vactrol,
by soldering the same vactrols back in!
More seriously, the mode of failure might be an indicator - was it 
sudden or gradual failure when the temperature went up?
I had a bunch of NOS vactrols from the early days, and a number
of them had gone (very) out of spec over the years. I suspected
moisture had gradually got through the mystery plastic case, but 
I couldn't say for sure.
paul perry melb Australia