Well, I figured out how to get the tube covers off. I just needed to spin them until the tab on the cover lined up with the slot on the chassis and they popped right off. I wanted to check the first two tubes, particularly V2, because I thought the overdrive channel was getting too noisy. It seemed to be glowing brighter than the others. I replaced it with one of the original preamp tubes from my JCA20H and the extra noise went away. Pays to have a spare.