Hello! I recently came into possession of a Heathkit SB-230 amplifier. Everything in it seems to be stock with the exception of the high voltage supply electrolytic capacitors. They've been replaced at some point, but I have no idea when. Looks like at least a decade ago. My questions are as follows: There is no grid protection circuitry. While this would be nice to take care of the tube if there are any overdriving/tuning mistakes, is it really that critical so long as tuning up is done at low power, and the amplifier isn't overdriven or doesn't see excessive grid currents? I have read that people are installing a low value, high power resistor in line with the B+ supply to the tube anode. What type of resistor is being used here? Carbon film or similar? Regarding the B+ resistor, how much protection are you actually getting from it? I ask since there is a decent sized choke in the B+ supply before the anode. Would a good power conditioner (from 120V or 220V) eliminate the need for this B+ resistor? Are there any other components which are notorious for wearing out and/or failing in the SB-230? I'd like to do a good job preserving this amplifier and especially the tube! Also, any hints or tips would be welcome. Thanks in advance, and 73 from AD5GG.