11-02-2005, 12:07 PM
Hi Ed
I see you are getting B+ to G2 of the 6A7, so we're looking for a common symptom to loss of B+ to G3-G5 of the 6A7, and to the screen grids of the IF amplifier tubes (Type 39/44). This rules out the choke (59). Coils are probably O.K.
SO...my first thought is that either resistor (57) has gone infinite, or there could be a wiring error. (57) forms part of a voltage divider network that drops the B+ going to the screens of the 39/44 tubes and to G3-G5 of the 6A7. You said you replaced all of the capacitors, so that probably rules out a shorted screen bypass (22). It's unlikely, but resistor (56) could be shorted? Check out (57), make sure (22) and (56) aren't shorted, and let us know what you find.
EDIT: Noting your lower cathode to ground readings on the 6A7 and 39/44 tubes, I am assuming they are low due to the tubes not conducting because of their lack of screen grid voltage; but did you replace those flexible wirewound resistors ( 8 ) and (21)? If not, you should. Also check ALL of your resistors, and replace any that are more than 20% out of tolerance. Nevertheless, start your troubleshooting with the suggestions made in the paragraph above before you go any further.
I see you are getting B+ to G2 of the 6A7, so we're looking for a common symptom to loss of B+ to G3-G5 of the 6A7, and to the screen grids of the IF amplifier tubes (Type 39/44). This rules out the choke (59). Coils are probably O.K.
SO...my first thought is that either resistor (57) has gone infinite, or there could be a wiring error. (57) forms part of a voltage divider network that drops the B+ going to the screens of the 39/44 tubes and to G3-G5 of the 6A7. You said you replaced all of the capacitors, so that probably rules out a shorted screen bypass (22). It's unlikely, but resistor (56) could be shorted? Check out (57), make sure (22) and (56) aren't shorted, and let us know what you find.
EDIT: Noting your lower cathode to ground readings on the 6A7 and 39/44 tubes, I am assuming they are low due to the tubes not conducting because of their lack of screen grid voltage; but did you replace those flexible wirewound resistors ( 8 ) and (21)? If not, you should. Also check ALL of your resistors, and replace any that are more than 20% out of tolerance. Nevertheless, start your troubleshooting with the suggestions made in the paragraph above before you go any further.
--
Ron Ramirez
Ferdinand IN
