Vintage, Swedish-made RIFA capacitors should always, ALWAYS be replaced no matter if they are working or not. These are frequently used for EMI filtering across the mains (AC) input into many types of equipment and are found in vintage audio gear quite often. Here's what they look like when the fail:
Most of the time you'll find them with cracks in their casing, which means they are pretty close to death. When these die, they tend to go catastrophically and emit huge volumes of smoke while they hiss and gurgle, expelling their guts. I have seen them in oscilloscopes, turntables (mostly "Dual" brand) and various amplifiers and receivers. Sometimes they are across the mains wires coming into a cabinet and other times you will see them directly on a power supply board. The examples above are out of a 1975/1976 Luxman C-1000 control amp (pre-amp) that was being restored. RIFA ceased capacitor operations around 1988. RIFA AB - Wikipedia. They can be replaced with modern film capacitors of the same values of capacitance and voltage. No matter what...replace them!