Adjustable bias board question

[Esquirefreak]

So, just a thought I had, hoping that some wise people would chime in on.

The "A" version is something I saw Uncle Doug do (if I remember correctly) on a 6G3.

The "B" version is (if I got it right) the typical Fender way of doing it.

Are there any pros or cons, over one vs the other? Don't focus on the R values, I'm more interested in understanding the concept of the circuits.

I'm putting together a 6G2, hence my curiosity.

Greetings from Sweden!

/Max

[sluckey]

Didn't u. doug explain why he used that circuit?   

Circuit A is preferred by many tech people because if the pot wiper fails, the bias voltage rises to maximum and will bias the output tubes very cold. No damage.

If the pot wiper fails in the Fender circuit, all bias is lost and the output tubes will self destruct.

Having said that, I've never read about a Fender pot wiper failure that damaged the output tubes. (But it could happen)

[thetragichero]

type a should have unused bias pot lug connected to the wiper, correct?

[sluckey]

I prefer to do that but in this case, it's not necessary.

[Esquirefreak]

Yeah, he did explain it, and I understood why he did it that way. Sort of a tree-climber-safety-net.

I honestly just didn't understand how the Fender circuit works. But I'm guessing the pot divides the voltage between the 27k resistor and ground?

So I just jumper lugs 1 and 2 on the bias pot for the A circuit?

/Max

[sluckey]

yes