Re: 6L6 turned purple, making noises... ?!?
Biasing is a range. If you re replacing JJ's with jj's you might be okay. The rating of each tube should be written on a little sticker on the box of each tube. As long as the ratings are pretty similar, you'll be fine. Some tubes can have quite a big difference in rating, and a rebias is the way to get the best out of your amp and the new tubes. But its nice to have a bias meter, cos its a quick and easy way of getting the exact number.
As far as sticking your hands in the amp....a bias meter's sockets go on the outside of the amp, then you plug them into your multimeter. If the bias adjustment knob is on the outside of your amp, then its super easy. If not, when you go inside, just be careful not to touch the big fat filter caps. They are easy to see, but on a lot of amps they are stored under the doghouse cover so you cant get to em. Try not to touch the pins on the power tube sockets and you wont get zapped. Having said all that, draining the filter caps is an easy job. Google how to do it. Also, when you are working in there, have one hand in your pocket. Its really not as dangerous as people make out if you take the time to learn how to be safe and take the proper precautions.
