This is a '77 Princeton Reverb in great shape (non pull-boost). The chassis was probably never pulled out before I did to replace all electrolytics. I also installed a 10k pot to adjust the bias. However with 30ma bias I get 485v on the plates! (with a pair of JJ's 6V6 and the original 5U4GB rectifier). I swapped the 5U4GB for a 5Y3 and with 25ma bias the voltage dropped to 450v, still high for a Princeton reverb, no? I'm thinking of swapping the bias resistor going to the bias pot for a 18k to have a little more bias range (it is already lowered to a 20k), but how high can I go on the bias to drop the voltage on the plates? PT is pretty cool to the touch, but the 6V6's and 5Y3 are pretty hot, of course. Before I worked on this amp I thought it sounded pretty sterile, with an unpleasant break-up. Now with the 5Y3 break-up sounds great, but of course headroom is diminished. Any advice? Am I endangering anything here? The amp came to me with the original tubes, actually original everything, and seemed to have been hardly played at all.