Had a similar experience with an old Sony. We were cleaning the shop and
dumping old junk. We had several televisons. We thought it might be fun to
take out our frustrations with a sledge hammer. A Hitachi required a tap.
Same for the JVC. When we got to the Sony, we all exhausted ourselves.
Finally a burly manager type came out and gave his all. It cracked. Then
the rest of us were able to do some damage.

Because the Sony tubes have always been flat (at least in one direction)
they have very thick glass for the screens. By the way, the backsides are
every but a fragile as any other tube (experience speaking....oops).

PoD