External biasing wiring?

[straycat]

Putting together an express and have some questions. I have an 50k 10 turn external bias pot that I will be mounting similar to the komet.The pot has three leads one on the end of the resistor,one in the middle of the resistor ,and the last one goes to ground.Does the top resistor one go to the 47k resistor on the power board? Where would the middle resistor and ground go to?If all of the wires needed go to the power board should I twist them. Would routing the wires along the back of the chassis be ok?

Also putting external probes in.Which pin on the output tubes do you mount the red probes to?Is it ok to mount ground to output tube socket ground?

Similar setup like this thread http://ampgarage.com/forum/viewtopic.ph ... light=bias

[Allynmey]

The wire goes from pin 1+8 from the tube socket to the red bias tip on each side. The ground attaches to the black bias tip. In between each red tip and the center black tip goes a 1 ohm precision resistor at 3W or higher. the Express uses 25K pot. If you need one I think I have some 20K 10 turns. I'll trade you. I could use another 50k for a Komet build.

Allyn

Here's a pic

[KGW]

Putting together an express and have some questions. I have an 50k 10 turn external bias pot that I will be mounting similar to the komet.The pot has three leads one on the end of the resistor,one in the middle of the resistor ,and the last one goes to ground.Does the top resistor one go to the 47k resistor on the power board? Where would the middle resistor and ground go to?If all of the wires needed go to the power board should I twist them. Would routing the wires along the back of the chassis be ok?

I would do it like this:

1 - from bias supply cap
2 - to 220K resitors on the board
3 - to 47k with the other end of the 47k going to ground

This is shown in the Komet amp pics.

BTW, I am going to do the same but with dual bias pots (like I did with my 1987)

[straycat]

Allynme thanks for the info on the pin location ,already have the jacks and resistors.Thanks for the offer on the 20k 10 turns but I am just going to use the 50k 10 turn clarostat pot that I already have

KGW thanks for the info .I looked over the Komet pictures and your suggestion would work in an express build. I am just looking for the wiring of a clarostat bias pot for pins 1,2,and3 that fits into the express board mounted bias pot scheme of things.

This is my first amp build if anybody can help with this I would appreciate it.I welcome all suggestions !!!