Blues Deville Bias question?

[retrorod]

Hey all! I have a Fender Blues Deville 2X12 combo in for service. This the schematic....

http://www.webphix.com/schematic%20heaven/www.schematicheaven.com/fenderamps/blues_deville.pdf

This amp has no bias pot or bias check point marked on the board.

It seems that any tubes up til now have been running hot. I use a Bias-Rite probe. Today, I tried a match pair of JJ 6L6GC and they are at 39-40 ma @472VDC.

I would like to install a bias pot....
Two questions....what resistor # for the pot and where is the test point for the recommended 68mv...?

Thanks for any direction or clarification,
Rod

[Jazz P Bass]

http://music-electronics-forum.com/t17305/
Enzo was kind enough to take this on in a previous post.

[Enzo]

40ma at 472v gives me 19 watts dissipation. If you go by the 70% rule that people like so much, you would have your tubes at 21 watts anyway. You may wish to reduce the idle current if you like, but it is not excessive as it sits.

[retrorod]

Thanks so much for the input. The measurements I stated above are with a new pair of JJ6L6GC. I left the amp running for 12+ hours with no blown fuse or bias drift. The PT gets hotter than hell on this amp though!

[Enzo]

Lots of them do.

[Jazz P Bass]

If you have the equipment, measure the current draw that the amp pulls from the mains.
80 watts is about normal.
If it is pulling 100 watts, then I would do something about the bias setting.