Changing new 'Fender'input jacks, that are soldered onto the PCB, to the 'old style' Switch Craft shorting jacks.
This affords better musical instrument input jack connection, and less noise in the system. The original plastic jacks that come with the Blues Deville, and Blues Deluxe (among many) are the 'Acillies' Heel' of this amp style. It's very easy to remove the old jacks and put in some reliable Switch Craft replacement jacks.
This is the schematic presentation of the 2 input jacks for a Fender amp
This is what the jacks actually physically look like on the back side of the chassis
...and this is how to hook up Switch Craft jacks to the PCB. Wires from the jacks are soldered onto the indicated PCB locations with 2 - 6" wires. These 'new' jacks will last a LOT longer than the amp they're going in...