K4040

Kits Audio Hi Fi Projects
1

I have readjusted the bias current of the power lamp el34. with RV1 etc and dipswitch ‘on’ until led 4 and 5 lihted but with the old lamps el34.
I have only 0.34 VDC on R. 97 and 0.34 VDC on the other points.

Question 1: Bad orther good?
Question 2: When I replace the old lamps EL34 with new EL34, is it necessary to regulate is new.

Good W.E.

2

Looks like a bad or off-spec tube.
Always re-adjust the bias when you change the tubes.
Also, check the bias once in a month.