Most of Fenders popular mid range amps like Twin 65, Hot Rod, Blues Deluxe and Junior are fitted with cheap plastic Jack sockets. They are really prone to breaking if gigged regularly.
A simple upgrade is to upgrade them with the vintage style metal chassis jack made by switchcraft as used on most guitars and all the old fender amps.
The nice thing about this upgrade is you feel the benefit every time you plug in and play.
Some amps like to have an isolated jack to help tame noise and this is also possible using switchcraft jack sockets and isolating washers. This prevents multiple signal ground connections to the chasssis and helps to minimise the chance of an earth loop and resultant noise.
In the picture below you can see that socket 1 has been replaced and socket 2 is original on a Hot Rod Deluxe. 
