Trying to put some 6V6 tubes in my Two Rock Ruby...never biased an amp before, but I think I can pull this off with maybe a hand or two. A few questions: 1) There is a bias test point next to the bias pot...the positive probe goes there, where does the negative probe go? 2) How exactly do a measure "ma" on my multimeter? I'm not seeing any obvious setting for that. Thanks for any help.