10-30-2014, 07:00 PM
First, let's start with a link to the schematic of the 39-70. http://www.nostalgiaair.org/PagesByModel...013302.pdf
First thing I see is that all the filaments were originally wired in parallel to ground rather than in series, so the first thing to look at is the way the filaments have been rewired. To do this properly, first let's look at the data on the tubes you have.
35Z3 AC rectifier... 50L6 audio output amp, replaces the original 1C5.... 12SA7 pentagrid converter would replace the 1A7 of the original... the 12SK7 is used as the IF amp in place of the 1N5... the 12Q7 is used as the 2nd detector, ist audio amp in place of the 1H5. You can find data on all these tubes here http://www.nucow.com/Free%20Tube%20Data%...20data.pdf
I will leave it up to you to check if the pinouts match, and how closely. Please keep us posed on the developments of this project. It is really interesting.
First thing I see is that all the filaments were originally wired in parallel to ground rather than in series, so the first thing to look at is the way the filaments have been rewired. To do this properly, first let's look at the data on the tubes you have.
35Z3 AC rectifier... 50L6 audio output amp, replaces the original 1C5.... 12SA7 pentagrid converter would replace the 1A7 of the original... the 12SK7 is used as the IF amp in place of the 1N5... the 12Q7 is used as the 2nd detector, ist audio amp in place of the 1H5. You can find data on all these tubes here http://www.nucow.com/Free%20Tube%20Data%...20data.pdf
I will leave it up to you to check if the pinouts match, and how closely. Please keep us posed on the developments of this project. It is really interesting.
