[Amps] Alpha 76/78 Filter Cap Question

[Kevin LaHaie]

OK, here's another possible trivia question!

I am re-capping an Alpha 78 for a friend, and I did my 76 already.  Nice 
to have identical or double capacity parts available from the original 
maker at pretty decent prices.

My Question:

There is an additional insulation 'sleeve' around the bottom half of a 
single capacitor in the 6 cap bank, it's the one that is on the right 
rear side of the bank (when looking at the amp from the front).  Any 
photo on the internet will clearly show this 'black' sleeve on the 
otherwise blue insulation on the Mallory caps.

Why is this there?  The caps are sitting on an insulated pad, and don't 
touch each other.  Hmmmm....

Anybody know why?  Mainly curious, it will be replaced during the 'recap'.

73 Kevin K7ZS