[Heath] Longevity of Apache TX-1 Modulation Xformers

[digital-conjurers at roadrunner.com]

Anyone know why these seem to be always in such demand?  Was it:

1) A design flaw (under-rated), or
2) The predilection of some AM enthusiasts to "open up the bottom end" of 
the 'Scratchy Apache', possibly leading to increased current flow in the 
thing, and blowing it out prematurely thereby?

Just curious.  I'm no Engineer.  :)

73 DE Lin/KJ6EF