I have a Marshall Bluesbreaker RI I just retubed and(tried) to bias. Im in Japan where wall voltage runs 100V 50Hz The plate voltage measured between 330-340V, and the hottest I could Bias the amp to was 33mA by maxing out the bias pot. Theres a Japanese sticker on the amp which says 100V 50Hz, but also an English sticker on the chassis which reads 120V 60Hz. My guess is that Marshalls imported to Japan come in with North American spec 120VAC transformers. Am I correct in assuming the 20% wall voltage drop would equate to the same 20% plate voltage drop? If so would a 20% increase in wall voltage give me a 20% increase in plate voltage, putting my plate voltages in the 400V range and allowing me to bias to a better spec? Any suggestions besides using a step up transformer to go from 100V to 120V wall voltage to plug the amp into, and biasing for a wall voltage of 120V using the step up transformer? Anything else I might be missing? Thanks! As a footnote My Ampeg Superjet which I know has a 100V transformer in it read 400V and I biased it just fine to 42mA.