12-10-2021, 08:01 PM
To check my IF is right on, I set my digital receiver to exactly TWICE the IF frequency of the set I am aligning. If the IF is 470KC, then I st the digital receiver to 940KC.
I then tune my frequency generator, set to audio modulation internal, to the IF frequency, in this case 470KC,, and connected to a short test work output antenna and carefully adjust it until I get the maximum sound output on the digital receiver. (Make sure your signal generator has THOROUGHLY WARMED UP, at least a half hour, so it won't drift !) Now you know your signal generator is putting out the proper frequency.
I then follow the manufacturers instructions for aligning the IF, or use this general method. If the radio uses a mixer/oscillator tube like a 6A8, I pull off the cap connector to the control grid, and directly feed the output of the signal generator into the control grid through a .001 MFD condenser. Set the output of the signal generator to the lowest setting that gives a clearly audible tone through the set being adjusted. I then peak the first and then the second IF transformers until I get the strongest audio signal through the speaker. You can use a voltmeter set to AC volts across the voice coil for this, or do it by ear if you have good ears. After I peak the second IF transformer, I go back to the first and adjust it again as necessary. I check back and forth a couple of times.
That's it, when both of the IF transformers, or all three if it has a two stage IF strip, are adjusted for maximum peak, you're all set.
I then tune my frequency generator, set to audio modulation internal, to the IF frequency, in this case 470KC,, and connected to a short test work output antenna and carefully adjust it until I get the maximum sound output on the digital receiver. (Make sure your signal generator has THOROUGHLY WARMED UP, at least a half hour, so it won't drift !) Now you know your signal generator is putting out the proper frequency.
I then follow the manufacturers instructions for aligning the IF, or use this general method. If the radio uses a mixer/oscillator tube like a 6A8, I pull off the cap connector to the control grid, and directly feed the output of the signal generator into the control grid through a .001 MFD condenser. Set the output of the signal generator to the lowest setting that gives a clearly audible tone through the set being adjusted. I then peak the first and then the second IF transformers until I get the strongest audio signal through the speaker. You can use a voltmeter set to AC volts across the voice coil for this, or do it by ear if you have good ears. After I peak the second IF transformer, I go back to the first and adjust it again as necessary. I check back and forth a couple of times.
That's it, when both of the IF transformers, or all three if it has a two stage IF strip, are adjusted for maximum peak, you're all set.