02-14-2013, 05:00 PM
Thanks for the kind words, Stephen.
I just looked up both 38-116 Service Bulletins (codes 121 and 125), and yes, I see where Philco says the output meter should be connected between plate and cathode of one of the 6L6G outputs. Connecting your output meter across the plates of both output tubes will also work in any set with push-pull audio output tubes.
I see also where the instructions call for the "Attenuator" control of the signal generator to be set for maximum output in both Bulletins. This has to be a mistake. If you set your signal generator to blast its strongest signal through the radio, between the AVC and the overloading of the extra strong signal, you will never be able to achieve optimum alignment.
I use an old Clough-Brengle signal generator with a B+K frequency counter hard-wired to it, and I have found that if I turn it much more than 1/4 turn above minimum in terms of output from the generator, it will overload the radio under test. Other generators may vary.
Using the weakest possible signal from your generator will prevent AVC from coming into play, as you correctly pointed out.
I use an oscilloscope for alignments, and have used one for years now. But you can achieve the same results with any good analog VOM or VTVM.
I just looked up both 38-116 Service Bulletins (codes 121 and 125), and yes, I see where Philco says the output meter should be connected between plate and cathode of one of the 6L6G outputs. Connecting your output meter across the plates of both output tubes will also work in any set with push-pull audio output tubes.
I see also where the instructions call for the "Attenuator" control of the signal generator to be set for maximum output in both Bulletins. This has to be a mistake. If you set your signal generator to blast its strongest signal through the radio, between the AVC and the overloading of the extra strong signal, you will never be able to achieve optimum alignment.
I use an old Clough-Brengle signal generator with a B+K frequency counter hard-wired to it, and I have found that if I turn it much more than 1/4 turn above minimum in terms of output from the generator, it will overload the radio under test. Other generators may vary.
Using the weakest possible signal from your generator will prevent AVC from coming into play, as you correctly pointed out.
I use an oscilloscope for alignments, and have used one for years now. But you can achieve the same results with any good analog VOM or VTVM.
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Ron Ramirez
Ferdinand IN