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What you are measuring is residual 21.25 MHz which managed to get thru to the video detector load resistor. R119 is the load resistor where the demodulated video signal appears. It is this signal voltage which is amplified by the video amplifier and then fed to the kinescope for display.
As I mentioned before, the detector load resistor signal ground is at -120 volts DC. The reason is the video amplifier is DC coupled to bring the DC component to the picture tube. This means a DC restorer tube is not required. You must understand this. If you do not ask further questions.
When you are adjusting the traps, because the signal is being sucked out by the trap, it is should normally be at a very low level when measured at the video detector. That is likely why you cannot see it. The alignment instructions are a only guide and you must understand what this all means. Because it is a trap and you do not see anything on the VTVM, did you try raising the signal level until you saw the needle deflect? Alternatively, if you reduce the -4.5volt bias to provide more gain, that would raise the signal enough so that you would clearly see the null as you adjust.
Let us know if you do not understand.
Last edited by Penthode; 10-12-2024 at 12:59 AM.
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