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

[Penthode]

Originally Posted by Chris K

I went back to the very beginning to work my way through and I ran into an issue with one of the trap adjustments. For all of the traps, I could stay on either the 1.5 or 5 volt setting on the VTVM and tune the slug for minimum voltage. I’m not with the TV right now so I can’t relay specifics but after cruising through 3-4 slugs, I ran into one where I had to up the VTVM scale to 50V DC to find a range where I could adjust for a minimum. That’s probably indicative of an issue wouldn’t you say?

The issue which happens with this chassis is that if the circuits are not stagger tuned, there is the chance of feedback. The loss of proper stagger tuning comes when someone adjusts a circuit and are not sure what they are doing. I have received sets like this. And the cure is straight forward especially with the precise equipment you are now using.

I will wait for more details so I can be sure what is going on.

[Chris K]

Weekend got busy. Be back on it Monday and Tuesday during the day. Thanks so much!

[Chris K]

I went through all of the steps through the video IF and trap adjustments that are done from the top of the chassis (step 11 on the alignment table). I was able to do all of the minimum voltage adjustments with the VTVM on the 1.5V scale. The signal is being fed into V102 pin 1 at 300mv through a 1500pF ceramic capacitor.

The max/min swings on the VTVM while adjusting the slugs were pretty minimal. That didn't exactly fill me with confidence! Could my input signal strength be too low at 300mV?

I have not encountered the problem described earlier where I had to increase the VTVM DC range to 50V. I must have seen that while going through the adjustments on the bottom of the chassis for maximum deflection on the meter.

[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.

[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.

[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

[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!

[Penthode]

Whoa! You are jumping too fast here and making wrong assumptions.

The trap nulls are pretty obvious and should be more dramatic. You should aim to getting about two to four volts across the detector load on the VTVM. The trap is nulling out. If so you increase the signal level until you see a good null. Did you do all the traps properly? It is very important before you move on.

[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???

[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]

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!

[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.

[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.

[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!!!

[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.