Not sure but the bingo i got ( that fell apart on lifting) had a big arse 500W transformer in it.. laminations may have broken down a bit with the extra draw on it.
From memory, the zener on a BALLY display is only rated at 1W, so the draw on these youd expect to be 3/4 of that at most.. the old plasma displays are actually very efficient and many lasted over 30 years, with continuous use for the first part of its life when it was sited.. thats pretty hard to fault
