This is an area where my experience is badly lacking - I have an AL-572 amp which is about two years old now. It has served me well, but over the past few months I've seen the grid current go down (the meter shows 10-20mA) and power output is down to 300-500W on most bands. Tuning is the same on the Plate control, but the Load control is now lower and lower on all bands, and nearly zero on some. This is into a 50 Ohm dummy load, or my antennas (which are all well matched to 50+j0 Ohms at this point). I've found a few posts, and some info on W8JI's site. I've ordered a set of replacement tubes. Today I opened the amp up, and made sure the tube sockets were all tight. All the filaments light up. The amp is wired for 120V at this point, but output is low even for this supply voltage. (HV is in range) Other than putting in new tubes and trying it out - are there any suggestions? The amp is usable. Intuition tells me that one or two tubes are bad, but I can't tell by looking. Re-seating the tubes and sockets did not help. Visually, everything looks fine, solder connections good, etc. 100W Drive Any advice appreciated, thank you.