Postby Beck-Ola » 08 Jul 2010, 14:23
That's tough. Replace them in corresponding pairs at the same time. They may not bias up close to each other otherwise, for one thing. It's best to keep them in pairs so they have the same amount of wear too. Even though there are four of them, the corresponding pairs work together.
You'll need to check the bias also, which is akin to setting the idle speed on a car motor. All you need is a decent volt meter. There are handy points in the VM where you take a voltage reading, which because it's taken across a precision 1 ohm resistor, can be directly converted to amps (Ohm's Law), which is what you're concerned with. I.e., I (amps) = E (volts)/1 in this case. There is a small pot to adjust the current with the range being between 72 to 80 mA. That's it. The most difficult part is getting the chassis out of the cabinet.
There are past posts you can search that give a detailed account of the procedure so make sure you read and understand those before attempting this. It must be done with the amp fired up. The voltages in there are around 450 volts (potentially even with the amp off!) so make sure you know what you're doing and work safely to avoid electrocution. :high If you're not sure, get an experienced person to help you.
Against stupidity the very gods themselves contend in vain. ~ Friedrich von Schiller
Kind of know how he feels.