I agree with Johnson. If you only have 1 volt drop across that regulator, it could be shorted.
Why the regulator is shorted might be the bigger problem. They normally go short from too much current draw in the load, which means you might fix the regulator only to reveal the load problem... the root cause.
When the current draw gets REALLY high, they first short out, then blow open, so it is not likely an extreme overload.
They can also go short because they have exceed thermal capacity, they got too hot. Older gear can have age related problems with heat sinking that causes thermal death.
Or in some cases the design was just pushed a bit outside of the envelope of the parts capabilities. Sort of an unintentional time-bomb. If that is the case, be prepared to replace it again in 2047. =-}