Whisker on a tuning gang

[Robert Darwent]

So I can only assume there was a whisker grown from one of the plates which the high voltage fused.

I had read about this but never come across it before. To be on the safe side I charged up a 0.1 mF to 500V and discharged this into the gang a few times.

That is reminiscent of the well known AF117 mode of failure, even the method used to cure the problem is the same.

I can only assume that a fine slither of metal has sheered off the leading edge of one the tuning vanes during use and caused the intermittent shorting.

It does make one wonder though whether the 'whisker' has grown by the same mechanism as they do inside an AF117 can? I believe the general opinion is that the growth is down to the semiconductor, but perhaps it is the aluminium after all which is the culprit!

It'll be interesting to know if it reoccurrs several months down the line, as it often does with 'zapped' AF117's.

Regards