JJ bias concerns

  • Thread starter Thread starter John4021
  • Start date Start date
want to try some kt77s in my smallbox 50, i have a bias probe but feeling a bit lost trying to find the trim pot.I see something similar on a mini board right around the effects loop jacks inside the amp...please help.Im old and blind or maybe i am lost and there is no trim pot?
 
Beandust":3j2nbpb8 said:
want to try some kt77s in my smallbox 50, i have a bias probe but feeling a bit lost trying to find the trim pot.I see something similar on a mini board right around the effects loop jacks inside the amp...please help.Im old and blind or maybe i am lost and there is no trim pot?
Click to expand...

The trim pot on mine is blue and almost directly behind the bass knob on the main board, it has "BIAS 50K" stamped under it in white.
 
marshall2553":xjwhjdz6 said:
Beandust":xjwhjdz6 said:
want to try some kt77s in my smallbox 50, i have a bias probe but feeling a bit lost trying to find the trim pot.I see something similar on a mini board right around the effects loop jacks inside the amp...please help.Im old and blind or maybe i am lost and there is no trim pot?
Click to expand...

The trim pot on mine is blue and almost directly behind the bass knob on the main board, it has "BIAS 50K" stamped under it in white.
Click to expand...
ok great i saw that but couldnt quite make out a phillips or flathead slot for trim adjust.so you would bias as a pair at 32 each or individually with the same trim adjust?
 
i used it seemed to adjust, i suppose i will use bias to set each tube to 32ma, will do a couple times to see if they drift.Thank you marshall2553
 
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