It could have been overloaded all the years until it finally died. Also, the secondary controllers might have gone bad and draw more amps than they used to in 1980 - do you have datasheets for them?
your new 100va trans is still overloaded!
did you measure current with a true RMS tool?
you can also measure the line side current of the transformer (true rms!) and see if your secondary measurements are correct (remember transformer losses).
Used my Fluke clamp-on DMM to measure current.
How long seems reasonable that a transformer like that could be overloaded before finally burning up - 1 year, 10 years, more?
