: Help !!!
: I've got all brand new tubes sitting on my workbench, and really need to know how to bias a Sentura I.
: I have a copy of the schematics, and I notice an adjustable pot accessable from the top of the chassis. I assume that's the bias pot ?
: What's the procedure to dial this amp in ??
: Thank you all very much !!
Mark;
For the non-technically inclined,I suggest the "bias-by-ear" method described by Gerald Weber in his book "A Desktop Reference of Hip Vintage Guitar Amps. Essentially it is as follows: plug in the correct tubes and the speaker (NEVER run a tube amp without the speakers connected....you could blow your output transformer). Set the bias adjustment (yes, it's the adjustable pot on top of the chassis near the output tubes) to the mid-point. Turn the amp on and let it warm up for a few minutes, watching the plates inside the output tubes. If these begin to glow cherry red, turn the pot counter-clockwise so they don't glow. Then you can set the pot at any position between below-cherry-red to fully counter-clockwise, depending upon the sound you prefer. For more technical adjustment methods see Gerald's book. Be aware that there are LETHAL voltages inside tube amps. So, if you don't know what you are doing, refer adjustment to a qualified amp tech. Hope this helps!
Ryan
