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

[Penthode]

Originally Posted by Chris K

No I didn't think so. I was injecting the frequencies at around 200mV into V2 Pin1 through the 1500pF cap. I was not getting swings anything like 1.0-2.0 volts DC. Is 200mV not strong enough???

200mV is way too low. I would go back and increase the RF signal applied.

[Penthode]

Originally Posted by Chris K

Well...in typical me fashion, I didn't encounter the need for the voltage range adjustment on the VTVM all the way through step 15 on the alignment table this time through. I was able to do all of them on the 1.5V scale. I had a difficult time turning the bottom adjustment for step 15, the bottom of T102. I didn't want to push it and break the coil/slug. I'm wondering if I should check the video and sound quality and if the sound and picture are in sync when a signal is sent in from my VA62 and I tune in the set channel for the RF input? I'm going to need help with steps 16 and 17 anyway. Pretty complicated for this numbskull.

Way too premature. You only check the picture and sound quality when you are finished.

[Penthode]

Originally Posted by Chris K

Checked the picture quality with the signal generator multiburst signal. I really don't know that much about this pattern except to read the vertical bars for resolution. From the right side, there's actually some vertical lines I can distinguish in the last 2 bars but I don't know if that's actual video. The third bar from the right has no resolved lines but from there all the way to the last bar on the left, there's good clean resolution. Sound and video still not aligning no matter how much the fine tuning is adjusted.

Note: Not signal generator...I meant video generator Sencore VA 62

As I said this is all too premature.

[Chris K]

Originally Posted by Penthode

Moving old ferrite slugs is fought with danger. The Canadian built RCA is is better than the US version as far as the transformer construction is concerned because in Canada they used brass threaded extensions to the ferrite cores. The US sets used slots in the cores themselves.

The adjustments should not need to be much the the stagger tuned cores (bottom ones) unless in the last 75 years someone has been there before.

For reluctant ones, I like to direct a heat gun with an aiming nozzle at the hole to warm it a bit. NEVER FORCE A RELUCTANT CORE. They are very brittle and easily snapped and are a devil to remove and replace!

Got it. I think my VTVM is a bit wonky. One more question...the channel selector is set between channels 2 and 13 but that's not a firm detent correct? I just have it between the two channels.

[Chris K]

Originally Posted by Penthode

200mV is way too low. I would go back and increase the RF signal applied.

What would you suggest...600mV?

[Penthode]

Originally Posted by Chris K

OK...not in any particular order...

1. How am I supposed to sweep the signal? The 2 frequencies, 22.05 and 24.75 are the peaks of the sweep in Figure 15 (and Fig 28 photo) and should be set in the marker generator correct?

2. Am I sweeping with a central frequency of 25mc a symmetrical sweep of 10mc? Is that what's required by the instructions "Sweeping 20-30mc" under the Sweep Gen Freq Mc column in the alignment table or am I reading that completely wrong?

3. Set bias -2V. Does that mean adjust the 250k pot for a reading of -2V at the R135-R136 test point as before?

4. Now for the biggie...shunt a 330 ohm resistor across the primaries of T-102, 103, 104 and 106. Does that mean connect 330 ohm resistors between the transformer tabs of the primary coils of all 4 of the transformers? How, solder them in? Please say no!

Here are my answers:

1. Yes this is the over coupled transformer link between the tuner and 1st IF stage. They advise you separately check and you are correct the peaks are 22.05MHz and 24.75MHz. Set the sweep generator to roughly 24MHz and set the sweep width to symetrical and widest seting.

2. No. What the instructions is saying is to roughly sweep to cover the bandwidth you are aligning. You want toe see the peaks and the srts of the resonse curve.

3. Yes that is it. Just be aware that you can overload the amplifier. Adjust the input RF sweep signal so that you get about 3 vDC at the detector.

4. I bought a bunch of 330ohm 1/4 w resistors and soldered small croc clips to either end. I then attached the croc clips to the terminals if the IF transformers. The reason for doing this is of course to remove the tuning of each IF stage so you can see the overcoupled transformer link performance.

[Penthode]

Originally Posted by Chris K

What would you suggest...600mV?

600mV where? I am talking about looking at the voltage at the detector, You increase the input until you see roughly 2 or 3 volts at the detector load.

[Chris K]

OK thanks. Going through the traps again. My probe clip connection was not solid. Seeing much more clear responses with changes in the traps. Meeting at 3p!!! Working hard here!!!

[Chris K]

Originally Posted by Penthode

600mV where? I am talking about looking at the voltage at the detector, You increase the input until you see roughly 2 or 3 volts at the detector load.

Wait...now I'm confused. I thought you were talking about increasing the strength of the RF output frequencies from the 8601. There's a lot of changes to the -4.5V voltage I set with the pot if I vary the output voltage from the 8601. Should I not even monitor that -4.5V?

[Penthode]

Originally Posted by Chris K

Wait...now I'm confused. I thought you were talking about increasing the strength of the RF output frequencies from the 8601. There's a lot of changes to the -4.5V voltage I set with the pot if I vary the output voltage from the 8601. Should I not even monitor that -4.5V?

Just set as per instructions and leave it. What do you mean lot of changes?

[Chris K]

Originally Posted by Penthode

Just set as per instructions and leave it. What do you mean lot of changes?

Never mind...I'm looking for too many things I think might be potential issues with just a rudimentary understanding of what I'm doing. I went through all of the traps again and saw good min/max on the VTVM. The minimum and maximum adjustments came with real swings on the meter and not subtle ones. There are a couple of things bothering me. When I tried to peak the secondary on T-106, I didn't see a peak until the adjustment was about half an inch screwed out of the bottom. I've done this about 5-6 times on this adjustment. I've run the slug from all the way in to about an inch of threads out on the screw. Where I have it now is the only peak on this secondary throughout the entire range of possible settings. The frequency fed into the converter grid is 22.5mc for this adjustment. I understand you said these shouldn't need to be moved too much but this one did. It's more than a bit possible I moved it when I was working on this over the past 2 weeks.

Mu other concern is the stiffness on the final peaking slug on the secondary of T-102 at 22.9mc fed in. It was really stiff so I didn't push it. Maybe I will try some heat as you suggested. I have a hot air gun in my soldering station that has a variety of tips so I can direct the heat exactly where I want it.

[Yamamaya42]

I'm getting confused just trying to follow all this.
As Penthode said, the -4.5 is set and forget, set at the start, and don't touch, or it will throw all things off, it's meant to suppress some circuits while you do the alignment, you do not need to monitor it.

[Penthode]

Originally Posted by Yamamaya42

I'm getting confused just trying to follow all this.
As Penthode said, the -4.5 is set and forget, set at the start, and don't touch, or it will throw all things off, it's meant to suppress some circuits while you do the alignment, you do not need to monitor it.

Setting it to -4.5v is simply fixing the AGC to a voltage close to normal operating voltage. The reason is that the IF response changes very slightly as you change the bias. Consider that the IF strip comprise of staggered stages employing the same vacuum tubes which have slightly different characteristics in the course of manufacture. In this world, nothing is perfect and engineering is always a practical compromise.

So the -4.5v is not an absolute. Is is a rough approximation of where it normally would be under average reception conditions.

(My philosophy: I often muse that in our digital world today, the display layer is what most now look at which is defined by a series of precise digital words which if is not corrupted in reception provides a closer to perfect ideal. Not so in the world of analog systems and television where the display layer doubles as the transport layer and is subject to vagaries like this.)

[Chris K]

Originally Posted by Yamamaya42

I'm getting confused just trying to follow all this.
As Penthode said, the -4.5 is set and forget, set at the start, and don't touch, or it will throw all things off, it's meant to suppress some circuits while you do the alignment, you do not need to monitor it.

Hey...me too! I got it about the "set and forget it" -4.5 volts. I'm not sure how Penthode would like to go forward. These settings are critical to the quality of everything going forward and I've gotta get it right. Maybe I'll post what's going on with pictures of each step and look for input from everyone and a consensus all is good before I go on to the next trap adjustment.

I've ordered some mini alligator clips so I can solder up 4-5 330 ohm, easy on/easy off shunts for the transformers in the last 2 steps in the alignment table.

[Yamamaya42]

Originally Posted by Penthode

Setting it to -4.5v is simply fixing the AGC to a voltage close to normal operating voltage. The reason is that the IF response changes slightly as you change the bias. So the -4.5v is not an absolute. Is is a rough aproximation of where it normally would be under average reception conditions.

That's what I thought, I did something like that with my Hoffman, the clip lead fell off on try #2, and I had to start all over again!
#3 worked pretty well!