I picked up a used AL811 from an estate sale and tried it out on 20/15/10 with fairly good power out. I had no idea how many hours the tubes may have had on them, but I started noticing drooping output power so I bought three new matched 811's and installed them. I also borrowed a friend's 1500W dummy load so I could go through each band to see what the pi-section control settings are. With the dummy load on the output, I can tune everywhere from the high end of 75-meters to 10 meters. But it will not tune down to the low end of 80-m, nor the 160-m band. The LOAD control, where it does work around 4 MHz, is set to approximately zero. It's like the LOAD side of the pi network needs more capacitance. At these frequencies, I cannot get the PLATE to resonate for any setting of the LOAD control. If I'm reading the schematic in the manual correctly, the band switch appears to be in the 160m position. It shows a C24 (500 pF, 1kV) and C25 (360 pF/1kV) that appear to be switched in on the LOAD side of the pi for lower frequency operation. I am suspecting that one or both of these caps is gone. Or the switch is bad. I suppose this is an easy thing to investigate. Does this sound like I'm on the right track?