Long time member, rare poster here. I've gained a lot of great information here. Recently completed my first ever full build of a Tweed Champ 5F1 using the Stew Mac kit. Overall great kit, but also some great tips I found on here, too (like standards to properly ground the main power cord ground to the chassis). The amp sounds great. Beautiful cleans at lower volumes and that special tweed Champ distortion when cranked. Really quiet, too, which I wasn't fully expecting on my first build. These forums and robrob's site have really driven my interest. I've already done the first few mods: treble bleed on volume control, 4.7uf bypass cap in V1 (didn't like 25uf), and swapped out the .022 Orange Drop coupling caps with Sozos. Curiosity next pointed me to digging in and measuring values to check tube bias. That's where things got weird... I've tried both the "Tube Dissipation Using Cathode Resistor Drop" and "Tube Dissipation Using Plate Current" methods, both with manual calculations and robrob's calculator. The numbers all agree and come out REALLY high: like 42 DC milliamps plate current and 125% plate dissipation. Here's some specific numbers: B+1 388 (this is the OT center tap voltage, right?) B+2 334 B+3 289 Plate voltage 375 (pin 3 on a 6V6, right?) This would mean I am getting a 13 volt drop (388-375=13) Transformer resistance (pin 3 to OT center tap): my meter reads .309K ohms, so this should be 309 ohms. Seems high, Rob's 5E3 resistance was 70-80 ohms. plate current = voltage drop/OT resistance, 13/309=.04207 amps, or 42.07 milliamps =========================================================== Moving over to the Cathode Resistor Drop method, I come up with the following: Cathode Resistor 463 ohms (as measured, rated as a 475 ohm resistor) Voltage drop across resistor 19.7 VDC Plate to cathode voltage 356 VDC (pin 3 to pin 8) I plug these numbers into rob's calculator and it yields 42.5 milliamp cathode current and 40.2 milliamps plate current, pretty consistent with the calculations above. Problem is, the plate dissipation per tube (=plate current * plate voltage) works out to .04207 * 356 = 14.97 watts. For a 12-watt rated 6V6, this would be a plate dissipation percentage of 125%! BTW, I also have a bias meter -- the type with an in-line octal plug that plugs into the amp's socket, then the tube plugs into the meter's socket. It reads about 42 milliamps. =============================================================== So, am I misusing the numbers in the formulas, or, wholly crap, this thing is running really high? I have not observed any red-plating on the tubes. One reason I am concerned (along with others) is I have some nice vintage tubes in there (a 1960's Phillips 5Y3 and a 1940's Raytheon 6V6). I don't want to fry those things after 20 hours. I have plugged other tubes in (the kit-included JJ's, a vintage Tung Sol 5Y3, modern production Tung Sol 6V6) and the voltages appear in the same ballpark (withing 10-15 volts), so no major differences. I have read in other threads one can run a resistor between the rectifier and the board to drop the voltage down (i.e. pin 8 of rectifier to first filter cap B+1). Is this an option? Or desireable? I'm really wondering what I should do here. Past threads confuse me...in one, posters are concerned a B+1 voltage of 367 is a concern, in another robrob said B+1 in a Tweed Champ should be about 390. What say the amp wizards who reside here? Thanks so much for any assistance!