If you have no frost on the evaporator coil while the compressor is running, that indicates a typical sealed system problem.
The sealed system consists of the compressor, condenser, evaporator, heat exchanger, filter/drier and refrigerant. Common problems with a sealed system are bad compressors, refrigerant leaks, and system restrictions.
Sealed system repair costs will often exceed the machines value. And at the age yours is now, it would cost more to fix than its worth.