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

[Penthode]

There is no real standardization. But in RCA lingo from other equipment, the parallel lines means a ferrite core and the arrows point to where it is to be adjusted.

[Chris K]

So what tabs on these things am I shunting with the resistors? I haven’t gotten a clear answer for that. I listed the setup and posted the schematic previously but I didn’t get any information. Is it the up arrow side of the coils being called the primaries?

[Penthode]

Originally Posted by Chris K

So what tabs on these things am I shunting with the resistors? I haven’t gotten a clear answer for that. I listed the setup and posted the schematic previously but I didn’t get any information. Is it the up arrow side of the coils being called the primaries?

The arrows pointing up mean the trap adjustment is on the top of the chassis. The arrows pointing downmeans the adjustment for the stagger tuned stage is made from under the chassis. Each stagger tuned stage has a resonant coil which connects to T102 terminals A/B and T103 terminals A/D, T104 terminals A/Band and T106 terminals D/C.

The resistors are placed across each stagger tuned coil. There is really no primary and I don't know why you are hung up on that. There is the stagger tuned coil and the parallel tuned trap mutually coupled to it. It is clearly identified on the schematic.

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.

[old_tv_nut]

Each coil connected through capacitors or otherwise to the tube circuits is a resonant coil. Saying that they are stagger-tuned coils only means that each one is tuned to a different frequency instead of all to the the same frequency (which is called synchronous tuning).

The coils that are connected to nothing except a single capacitor and nothing else are the trap circuits. These trap circuits can be called magnetically coupled or transformer coupled if you wish.

[Penthode]

Yep, yep and yep to the previous replies.
All that stagger tuning is is to have each tune circuit tuning staggered to obtain the desired wide bandwidth. Later, when you get to the point where you are frequency sweeping the entire IF amplifier, you will have to slightly tweak some of the stages to get the flat top shaped response with the frequency markers at the correct amplitude. And because the stages are stagger tuned, you will look at the response on the scope and adjust one of the stagger tuned stages corresponding to the part of the band to correct it.

[Chris K]

So my brain needs to flush all this out to be able to understand it. It’s just the way facts have to get processed before I get it. So when a signal with different frequencies goes through a circuit and you are trapping one or removing one with a trap coil, that coil, by moving an iron slug to the appropriate position within a winding will resonate at the desired frequency matching the signal to be filtered out. Is it the coil in circuit that is resonating at various frequencies including the one to be trapped and that energy is dissipated by the fact there’s an adjacent coil at just the right “stimulateable” resonance that essentially sucks the frequency energy out of the broader signal? It’s like a filter that hijacks the undesirable frequency out because it’s tuned to “pick it up” from the broadband family of frequencies passing through? Or am I lost somewhere in the asteroid belt!

[old_tv_nut]

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

[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?

[Chris K]

Just making a joke…not a very good one I guess. Sorry if I offended you.

[Penthode]

I am never offended. That was my joke in return. I hope it did not offend you.

Are you all set? A good part of the process is identifying the pitfalls and knowing how to get out of them. I try to (and not always successfully) abide by the rule if something doesn't look right, stop and think about it before proceeding.

[Chris K]

So I went back to step 6 in the alignment procedure just to be certain the adjustments I made to the top and bottom cores with the different frequencies fed into the converter grid were accurate and that the VTVM was reading the minimizing/maximizing accurately i.e. checking my work that I had the trap coils tuned to the correct resonant frequencies and the IF stages tuned properly. A couple of days ago, I posted the issue with the VTVM going off scale was tied to the signal strength going into the converter and with careful adjustment of the signal output I was able to tune the traps and stages accurately without the VTVM requiring a voltage range setting higher than 5 volts DC. When rechecking tonight, I encountered the same issue. I could not get the VTVM to read in the 5V scale when measuring across the video amp load resistor.

I believe I've found what is doing this but how and what is happening I don't know. The brightness control seems to be a problem. It is intermittently grounding out and sending full voltage through the yellow wire to the CRT. A bright horizontal line appears on the screen. Touching the shaft will cause the VTVM to jump way out of range. I don't know if this is what is causing the issue with measuring the voltage changes that happen when I'm trying to tune traps and minimizing at the R119 load resistor but when it happens, the VTVM pegs and goes off scale.

I don't see how sending full voltage to the CRT cathode could be causing the issue. The only possible link I see may be the fact the yellow wire from the control to the CRT cathode runs directly under the load resistor I'm measuring to adjust the frequencies in the various stages. This has been an intermittent issue since I started doing this series of adjustments and I guess, when I worked on it a few days ago and reported no problems, it wasn't happening. So at this point, I don't know if I even have the trap coils adjusted correctly. I don't know enough about what that voltage spike in proximity to a test point in this effort could do. I guess I could move the wire and see if it helps.

[Penthode]

Just to confirm, with nothing connected to the VTVM and it set to 5 volts, it still goes off scale?