Ok. Let’s try this again…RCA 9TC240 Alignment

[Chris K]

Originally Posted by old_tv_nut

You got it. The trap circuit sucks a narrow range of frequencies out of the broader circuit's response.

And it's the "passive" coil that does this? It does that because the slug and coil are positioned so its natural resonance is at the undesired frequency. When the powered broadband signal goes through the connected coil, the energy associated with the unwanted frequency starts vibrating the tuned passive coil. The energy needed to do this formally resided in the broadband signal at the trap frequency. It is transferred to the trap coil vibrating it and eventually dissipated as heat (Not that it's important...just trying to follow the energy)????????

[old_tv_nut]

Originally Posted by Chris K

And it's the "passive" coil that does this? It does that because the slug and coil are positioned so its natural resonance is at the undesired frequency. When the powered broadband signal goes through the connected coil, the energy associated with the unwanted frequency starts vibrating the tuned passive coil. The energy needed to do this formally resided in the broadband signal at the trap frequency. It is transferred to the trap coil vibrating it and eventually dissipated as heat (Not that it's important...just trying to follow the energy)????????

Yes

[Alex KL-1]

The wonderful world of the RLC circuits!

[Chris K]

Do you understand what you are doing by clipping in place the resistors? It is to eliminate the resonance of the stagger tuned coils so that the remainder of the video IF strip is just an untuned amplifier. This is so you can see independently the tuner over coupled transformer link frequency response when you sweep it. You must try and understand the process so so will be better able to identify and rectify any problems.

So what is it I'm stopping by attaching the resistors? Is it the resonant, in circuit coils or the trap coils? I sorta get the statement this makes the video IF stages an untuned amplifier but the statement "This is so you can see independently the tuner over coupled transformer link frequency response when you sweep it"is making my head spin. So when I sweep the input signal symmetrically 10mc with 25mc as the center frequency (from 20-30mc) and pick it up on the scope at the end of its travel through a detuned IF series of stages, I'll see the full bandwidth signal out at the end? If so why is that important to see and what then am I looking for to adjust?

[Penthode]

Originally Posted by Chris K

So what is it I'm stopping by attaching the resistors? Is it the resonant, in circuit coils or the trap coils? I sorta get the statement this makes the video IF stages an untuned amplifier but the statement "This is so you can see independently the tuner over coupled transformer link frequency response when you sweep it"is making my head spin. So when I sweep the input signal symmetrically 10mc with 25mc as the center frequency (from 20-30mc) and pick it up on the scope at the end of its travel through a detuned IF series of stages, I'll see the full bandwidth signal out at the end? If so why is that important to see and what then am I looking for to adjust?

The resistors temporarily shunting the coils will essentially make the IF amplifier downstream a broadband untuned amplifier. This will allow you to see only the tuner to first IF over-coupled link frequency response without interference. You want to be able to establish a correct response between tuner and first IF before adjusting the remaining stages. So the order of work is:

1. Confirm traps are correct
2. Sweep align the tuner to first IF over-coupled link with resistors shunting the downstream stages
3. Sweep align the entire video IF with the resistor shunts removed.

You should be cognizant of the fact that unless someone has in the past meddled with the tuner-1st IF link transformers, the adjustment should be close. Be aware that if any of the resistors are not connected or loose, it will distort the response you are trying to obtain.

Once the resistors are removed which will raise the gain of the IF amplifier, there is the danger of oscillation which they describe how to handle in the notes. The oscillation will occur if two of the stages are tuned close to the same frequency. The Video IF stages must be properly stagger tuned to be stable.

Here is a Wiki page describing stagger tuning.

https://en.wikipedia.org/wiki/Stagge...reduced%20gain.

[Chris K]

Originally Posted by Penthode

The resistors temporarily shunting the coils will essentially make the IF amplifier downstream a broadband untuned amplifier. This will allow you to see only the tuner to first IF over-coupled link frequency response without interference. You want to be able to establish a correct response between tuner and first IF before adjusting the remaining stages. So the order of work is:

1. Confirm traps are correct
2. Sweep align the tuner to first IF over-coupled link with resistors shunting the downstream stages
3. Sweep align the entire video IF with the resistor shunts removed.

You should be cognizant of the fact that unless someone has in the past meddled with the tuner-1st IF link transformers, the adjustment should be close. Be aware that if any of the resistors are not connected or loose, it will distort the response you are trying to obtain.

Once the resistors are removed which will raise the gain of the IF amplifier, there is the danger of oscillation which they describe how to handle in the notes. The oscillation will occur if two of the stages are tuned close to the same frequency. The Video IF stages must be properly stagger tuned to be stable.

Here is a Wiki page describing stagger tuning.

https://en.wikipedia.org/wiki/Stagge...reduced%20gain.

Thank you. I have not messed with T-1 and T-101 so hopefully they are close. Still not clear on where to clamp the resistors...for example, on T-102, I am putting the resistor between tabs A and B correct? I'm not shunting the trap coil correct?

[Penthode]

A caution I need to add with this particular chassis when adjusting the IF stages. The adjustments can be deceptive because when you are adjusting for a peak you may inadvertently be tuning two stages to the he same frequency which will cause oscillation. This oscillation can be easily mis identified as a peak. The way to confirm is always as you raised or lowered the deep generator input, the output put level should rise and fail. If when reducing the signal generator in you still see a signal which does not change when you vary the generator output, you have an oscillation condition you will need to address.