wow, I thought I was gonna be stuck with the expert village explanation. thank you oh thank you

Nice one, i mean this guy must have kept them the same as he didn't have to rebias them too much.

Thanks man :D

I'm used to working on old tube tv's so know the danger...2 places you don't want to touch are the pins on the underside of those tubes and the big capacitors in the power supply.

Capacitors can really zap you...I used to work in a repair shop and my co-worker touched a charged capacitor inside a microwave oven....the jolt was so strong it threw him back up agaisnt the wall. He was stunned but and lucky he wasn't hurt. It really scared me.

ok will do thanks very much

Neither volts nor amps can kill, it's the combination of the two.

@Sethsilva13 Tubes are usually "burned in"  during the process where the factory or distributor determines which ones get "matched" together. If you are really worried about it, you can just test them periodically.

@punkmusicmetal best thing for draining power when you turn it off would be to make sure theres a resistor, say 100-200k about 2w accrossthe first capacitor, most amps already have it but it could be too big, a smaller capacitor means more current draw means faster cap drain, but then thats still drawing current when the amps turned on so it cant really be too big...

@Giggity230 It usually just effects the performance of the amp.  It doesn't damage anything, just doesn't sound as good or get as loud.

Thanks - I had very tight 6l6 tubes and was worried about breaking them and did the circular wiggle and they slipped out!

I had a bad hum and crackle issue: I swapped all the 12ax7s and wasn't them, so I took the 2x 6l6s out, put some contact cleaner on pins,  swapped over their positions, re-inserted ( and wiggled!) and hum gone and no crackle!

correct. and if you own a mesa that came with 6l6's and there's an el34 switch on the back (or any amp, not a mesa) you can put el34's in and set the switch to el34's.
kt77's will also work in an amp that has an el34 switch because they run similar.

Well capacitors are of large capacity in amplifiers thus they store a lot of energy and voltage in them thus accidentally shorting them with yourself you will be cooked anyway.
Discharge electrolyte caps with 1W 50Kohm resistor. Use well isolated crocodile clamps to connect resistor to capacitor.

@punkmusicmetal  
Opinions vary on what is too far unbalanced with regards to good tone. Some people intentionally unbalance an amp. With regards to a properly functioning output section you would want each side to be within a 3mA of each other. You can usually drain an amp with a 10K 5w cement resistor and a set of test clips. Amp off strap the resistor across the first filter.

The old saying is "it`s the volts that jolts and the mils that kills"

@stevoe1000 On this one, it's only for one to match the other.  Alot of Mesa Boogie amps are prewired so no adjustments are necessary, and I'm not sure about any other amps.

TRUE It`s the volts that jolts and the mils that kills. No Voltage then no current. Current is proportional to voltage and inversely proportional to resistance and if they have changed it they neglected to tell me.

@Ynehc

Yes the combination. But a high voltage and really amps will not kill you. 1 million volts and 1mA will not kill you. But 230volts and 80mA will.

that looked pretty easy! are there different plugs for different tube sockets with the bias master so you can bias almost every amp? (sorry if i misspelled some words my english isn't that good)

You're right, just makes them wear out faster.  Maybe he wants his customers to keep bringing him business?

Nice does the amp need tone rebiased when just replacing the rectifier tube?