LCR meter

One tool I don't have is a LCR meter for testing capacitors as they are most likely to degrade. 

I have a 1970s amplifier which started to get a line voltage hum. 

I finally replaced all the capacitors and the hum disappeared. 

I never tested the old capacitors but they must have degraded significantly after 50 years. 

Has anyone actually measured old capacitors and then replaced them and noticed such a big reduction in hum.

I replaced the caps on a 20 year old parasound but it made zero difference.  It didn't exhibit any hum so I probably jumped the gun on that one.