Need some guidance. I am in the process of going through a 1939 National NTX-30 transmitter and NSM modulator. The original modulation transformer is long gone possibly due to a 6X5 cathode to filament short in the feedback circuit. I would like to duplicate the original mod iron and not modify the original circuit if possible. The design may be somewhat unusual in that the secondary is tapped for volume compressor voltage above the modulation output to the Class "C" NTX-30 finals. I attempted to contact Hammond's Peter Dahl department rep twice so far but no reply yet. I am willing to pay engineering expense if necessary and I realize the cost will likely be high. A copy of the National NTX-30/ NSM equipment manual is attached which has schematics and further explains the circuit. National calls it Class "B" in the manual which is now Class AB2 I think.
Thanks in advance, Greg
NSM Photo courtesy of KC8DDH