I like gutting those old can caps and installing new individual capacitors in the can. You get new capacitors and preserve the look of the unit by doing this.
Similar problem on my 6100 which eventually turned into an uncontrollable volume problem. Macintosh relied on crimped ground wires on the signal cable to provide ground. These crimps after fifty years go bad causing volume problems. I repaired the problem on mine by soldering a separate ground...
I bought my 6100 in 1975 and have been listening to it every day since. Other than some age spots just like me, It has given me nothing but enjoyment. System number two is an Mx113 powering a Crown D150