I was planning to do some work on my "Sweet Baby" JTA-05 Fender Champ clone but, having opened it up, I. can't see how I'm able to test or discharge the filter capacitors. The positive end of each is inaccessible, buried in the board below. See pic. I'd greatly appreciate any advice on how I can make safe this amp before starting work on it. As an aside, the mods I'm planning are a fixed bright cap across the volume pot (which I'm assuming I can get to around the back), a switch to remove/add negative feedback (R13), Rob Robinette's 10% power switch ( https://robrobinette.com/Generic_Tube_Amp_Mods.htm#10%_Power_Switch ) and a switchable 25uF capacitor over R4 (or C7).