Mesa Boogie Stiletto Trident Bias adjustment pot

[DanAngus]

Hey guys!
First post to this forum!

I am looking to change the tubes for the first time in my Mesa Boogie Stiletto Trident head.
I do not want to use Mesa tubes, because they are not top quality and are way over priced. i also think that they could be run a little hotter.

Im pretty new to electronics, but i know the basics.

I want to add a bias adjustment pot to the circuit so i can adjust the bias when retubing.

The problem: I dont know what resistor to take out, and add the pot in place of that resistor.
- what pot do i add?( 50k, 100k etc.)

Thanks for your help

P.s if anyone has the schematic of this amp that would be very beneficial!

[bob p]

It will be tough to find schematics online for the latest Mesa amps. IME your best bet is to call Mesa support and ask them for the schematic for your amp.

[Pedro Vecino]

Locate the pair of electrolytics 47uF/100V bias circuit next to the two big electrolytics 220uF/300V. On your left is a group of three resistors. Two of them in parallel over the last electrolytic bias (the closest to the line of the driver). On this point (common to the two resistors and electrolytic) you should find the bias voltage (-40VDC approx.) And there (paralleled) you can install a line composed of a 10K resistor (to set the minimum) and a 50K multi-turn potentiometer in series.
Remember that the setting is common for the 2xEL34 and 6xEL34 selection. You should check the flow in both selections to find it the best adjust (high voltage value changes with the selection). If I remember correctly, the pair of 50 watts is the outside (1/6)
This should be done in "diode rectifier" and bold mode.
To obtain a good bias adjust in tube rectifier mode is necessary to automate a second adjustment installed over the amp switching circuit (this is quite complex and would never recommend it if you do not have much experience).
Also remember that the original bias adjustment in the Trident is cold and with it the tubes are very relaxed (at least in 6xEL34 mode). Regardless of use can be found in perfect condition composing a good set if they maintain good symmetry.

Finally, with Marshall sounds in mind (classic, modern...) a good power tube selection with the best bias adjust provides in this amp a narrow relevance (for me, low) in relation to all aspects that handles the amp (textures, contours, string balance, balance between different modes, etc.).
Regards