BIAS adjustment screw in Einstein, any screwdriver safe to use?

[diddly]

Hi,

I have put some JJKT77 power tubes in an Einstein 50. Previously it had EL34's. Recommended bias is 70. The bias is currently 71 after putting the tubes in. I just need to adjust the screw to get it to 70. I just want to confirm if its ok to use any screwdriver that fits or is a phase tester screwdriver required?

Thanks

 

[phil b]

I just used one that fit and didnt have any issues. Being at 71 you could also leave it there without any problems. I found that over time my bias would drop slightly (1-2) so after a few hours you may find it right at 70. Good luck!