Hi all, I've got a Rivera Cluster 45 amp, last couple of days its been crackling and popping intermittently so I had a look at the tubes. 2 pre amp and 2 power amp tubes.... I tapped them with wood to see if I could see if one had gone off, but they all sounded fine. I unseated the pre amp tubes just to see if the contacts were corroded but they seemed fine. After reseating the tubes the amp is now constantly crackling. I'm in the UK and we are in lockdown for the foreseeable future so I can't take it to a repair guy. Would you think me unseating then reseating the preamp tubes and it now being worse suggests that one (or both) have gone bad? Or is my problem elsewhere? I've tried it with different guitars, different leads turned everything off that's near it and none of that has helped. Cheers for reading.