I have a '95 Mesa Subway Rocket that I just love that has the same problem that many EL84 amps have - it runs the tubes way hot and they're only good for about 3 or 4 months of regular use. About the only tubes that last very long are Sovtec EL-84Ms, but they don't' sound quite as nice as the JJs that I've been using. The schematic for the SR is here: http://www.freeinfosociety.com/electronics/schemview.php?id=295 The only mod that's been done by me is that I replaced the 470 ohm screen resistors with 1K 5-watt wire-wounds, which cooled off the tubes a bit and gave the amp a bit more compression, which I like. After the screen grid resistor mod, the plate voltage (pin 7) is about 392 (was close to 400!) and the screen voltage (pin 9) is about 315 (was 320). The bias (pin 2) measures at about -11.5 volts. Up less than half a volt from stock. A drop of about 5-6 volts from stock on the HV side. Not much, but apparently enough to make a difference to prevent mild redplating on certain types of tubes. I'd like to install a bias pot with a pot failure backup resistor in place of the existing bias circuit. This is where the amp experts on this forum come in. I've got some experience working on high voltage amp circuits, but it doesn't go real deep, just enough to track down and replace bad components, do minor repairs, mods and such. Most of what I've learned is by trial and error and places like this forum. So, if the experts can tell me what/where to change things on the schematic, I can make it so. Thanks in advance for any help!