Bias instructions Mastersound Compact 845

Used to have them, but.....never loan the original copy out. Lesson learned.
At any rate, there's a definite difference in volume between L and R channels. Going to swap out tubes, but I need to bias new tubes, and don't remember the bias setting. Anybody know? Think it was 15V, but uncertain. Any help would be appreciated. Mastersound's owner's manual doesn't tell you anything other than "don't change tubes with power on" and things like "don't stick your tongue in the tube socket" and other worthless stuff.

Thanks in advance!