When is alignment required?

[UberVacTuber]

Now that I've got the Admiral working well, I was wondering how to tell when an alignment is in order for a refurbished TV. I've seen some comments about re-alignment sometimes being needed after replacing resistors in the video output and tuner sections, but are there any other other things to look for?

[bandersen]

With these old split carrier Admirals one easy way to decide is see if you can tune in a good picture and sound at the same time. By split carrier I mean that there is a separate video and audio IF right after the tuner.

Try to watch some "crisp" video scenes and listen to some good audio. If it looks and sounds good to you, then I wouldn't bother with an alignment.

If you have a test pattern generator, you can use it to estimate your video bandwidth. I think the bars on the far right in this case are 4.2 MHz. Keep in mind some sets aren't designed to have that much bandwidth.

[ChrisW6ATV]

That is a nice, sharp picture from your set, Bob.

[bandersen]

Originally Posted by ChrisW6ATV

That is a nice, sharp picture from your set, Bob.

Thanks. That's from an Admiral 24A12 with a 20A1 chassis which uses a staggered tuned IF for really wide bandwidth with a flat plateau.

The 30A1 chassis used in the 30Axx sets like UberVacTuber's uses two peaked IF frequencies for a "double-humped" response. I haven't aligned one of these yet, but I expect it won't have quite as good a response.

On the other hand, this wide a response can be a bad thing. When you feed a color signal into this set you get dots - I think from the 3.58 MHZ color sub-carrier. Later sets had a color filter circuit of some sort I believe.

I read about a workaround elsewhere on VK to use the green component output of a DVD player fed into an RF modulator. It worked great for me

[Phil Nelson]

Ugh. I have not seen a dot pattern like that before. Waiting in my queue is an Admiral 24C15, which has a 20B1 chassis according to Rider's. I wonder if it will have the same response to color signals?

Phil Nelson

[ChrisW6ATV]

Yes, high-resolution B&W sets will show the chroma as various patterns of dots, and the solution is to use the Y signal from an S-video or component-video output of a DVD player or digital-TV tuner into a modulator. Once color TV hit in the mid-50s, I think they just started making all the sets with lower bandwidth in general, but I may be wrong. A notch filter on 3.58 MHz would have helped, but I don't know if they were used in B&W sets later or not.

[UberVacTuber]

Thanks for the input. The picture quality seems pretty good, and the audio is clear. Sometimes the audio is kind of weak depending on the source, so that's why I was curious. I can get the sound to come in stronger, but then I get distortion of the picture (the picture will twitch along with spikes in the volume).

The top of the picture looks a little wavy, although most of that can be straightened out with the Horizontal Hold. There is also a bit of shadowing on the right-hand edge of the picture tube, due to the ion trap. When I completely eliminate the shadow, the picture dims quite a bit. At maximum brightness, a sliver of the right side of the raster disappears. What you see is (so far) the best compromise I can get.

Here's a few screen shots using the Techpreservation test pattern DVD. They look better in person. Here's the "Indian Head"



And the TV Analyst:



Some linearity patterns. The circle looks a tiny bit egg-shaped on the right, but for the most part looks pretty good:





And lastly a still B&W image:

[earlyfilm]

Originally Posted by UberVacTuber

Thanks for the input. The picture quality seems pretty good, and the audio is clear. . . . . . .

Here's a few screen shots using the Techpreservation test pattern DVD.

Uber,

I think we have a little mix up in terms here.

I do not see an alignment problem with your pictures, but do see a lot of other adjustments off.

On a B&W set, alignment normally refers to IF and Tuner circuits, and unless you have the equipment and have done one before, I'd suggest that you have someone who has experience here watch you the first time you attempt one, because it is very, very easy to convert a small problem into a major one.

The incorrect adjustments that I see in your pictures are:

Neck shadow on right edge of the picture. (Possible causes: Yoke position, focus coil position and/or ion trap magnet position or weakness.)

re: The top of the picture looks a little wavy

Your sync seems to have a locking problem, which might be related to your linearity problems, but it probably is not. Substitute known good sync tubes. Try to get a schematic, like Sams that gives the voltages and check sync circuits. Suspect plate to grid caps of having leakage and you will have to open one end of them to check.

Once your sync is stable, trouble shoot the linearity issues.

Both the horizontal (do first) and vertical linearity adjustments seem off. If controls don't have enough range, suspect tubes first and then leaky caps. The Ryder schematic for the 30A1 on the ETF site gives good instructions for these adjustments.

Re: (the picture will twitch along with spikes in the volume).

Disconnect the speaker and put a 5 to 10 ohm resistor across the feed connector.
If this removes the video problem gently tap tubes in tuner/if/sync and video to see which one has gone microphonic. (Note: It is not necessary to put the load on the audio output transformer with a disconnected speaker, but on a tube set, it always is safer and a heck-of-a-lot less expensive than a fried output transformer.)

re: At maximum brightness, a sliver of the right side of the raster disappears.

Poor high voltage regulation. Check 1B3, horizontal output, damper, if check is OK, substitute a known good damper tube as testing.

Another less common cause of poor HV regulation is a gassy CRT, or leaking coupling caps in the grid circuits of the CRT.

Jas.

[UberVacTuber]

No mix up in terminology. Banderson answered my question and then the thread took a bit of a change in direction. Now that I'm getting good video I wanted to share it and compare it to his photos. I know you're being helpful with the suggestions, and I appreciate it. If I should have started a new thread instead, my apologies...

I don't have half of the equipment listed in the repair manual for the alignment procedure, nor did I intend to try it. After the comments given, it doesn't look like alignment is an issue.

I know there are still issues with the adjustments. I haven't had much time to do a lot of fine tuning. As I mentioned, the waviness is pretty much eliminated with the Horizontal hold. I hadn't fine-tuned it before I took the pics. The horizontal frequency has been adjusted per the instructions.

The ion trap is causing the shadowing. When I move it to a point where I get the maximum brightness, that's when the shadow is the worst. When I move the trap to a position that completely eliminates the shadow, the picture dims a fair amount. Are you saying that this is indicative of a high-voltage issue?

All the capacitors with the exception of the 10kV "Doorknob" for the CRT anode are new. I have both the Rider's and Sams schematics and the voltage and resistances check out OK. Originally I had too much width and the control had no effect. It turns out the damper resistor had failed and once replaced, the raster was the correct size and the controls then had good range. All the tubes in the cage check out good.

[kx250rider]

My rule of thumb is; alignment is only necessary in a fully restored vintage TV if someone has previously messed with the alignment. Normally, when you replace all the caps (including the Micamold "domino" caps in the tuner and IF sections), and you have verified that everything is working correctly, the TV will fall back into good factory alignment. This may not be true for early color sets, which are VERY temperamental with chroma/bandpass alignment. If you so much as replace a tube in the color or IF section, it might knock it a bit off.

Charles

[earlyfilm]

Originally Posted by UberVacTuber

The ion trap is causing the shadowing. When I move it to a point where I get the maximum brightness, that's when the shadow is the worst. When I move the trap to a position that completely eliminates the shadow, the picture dims a fair amount. Are you saying that this is indicative of a high-voltage issue?

Nope! Now, I've put my foot in my mouth, as I misunderstood your discription.

Reduced sweep at high brightness is often associated with incorrect high voltage regulation, although blooming is a more common result. Any power tube drawing higher current than it should could shift the focus coil current or cut your width by pulling down the "B" voltage. This failure mode usually leaves the edges more-or-less straight when the image reduces, not curved like the neck of your tube.

Lets first tackle the neck shadow issue.

Generally (curved) neck shadow issues are yoke/focus coil/ion trap issues.

First adjust the ion trap for maximum brightness and refocus.

Is your focus adjustment at the end of it's range as that may be a clue?

With ion trap in the new brightest position, try repositioning the yoke and focus coil to reduce the curved shadow. (Mark both exact positions prior to moving and do the yoke first.)

If this helps, then tweak the ion trap again for max brightness.

These adjustments sometimes shift when the set is transported, or sometimes have been shifted by a prior repairman to fix an unrelated problem.

Originally Posted by UberVacTuber

Originally I had too much width and the control had no effect. It turns out the damper resistor had failed and once replaced, the raster was the correct size and the controls then had good range. All the tubes in the cage check out good.

Are you talking about the multi-tapped 50 watt R435 on the Ryder schematic?

If not which one?

Since you recapped, did you replace the .5mfd off of your width control with a .47mfd? It is a small change, but it could have pushed the width coil beyond its limit.

Have you adjusted the horizontal drive?

Jas.

[UberVacTuber]

"Is your focus adjustment at the end of it's range as that may be a clue?"

I think we're getting there.. I had been moving the focus coil around quite a bit as I was having a hard time getting the picture centered. It is in quite close and the best focus is close to the end of dial travel. I'll try your recommendation RE resetting the ion trap and then resetting the focus coil. The deflector yoke is locked in place and the tube up right up against the mounting. The only adjustment available on the yoke is to tilt the raster in order to get it level.

"Are you talking about the multi-tapped 50 watt R435 on the Ryder schematic?"
Yup.

"Since you recapped, did you replace the .5mfd off of your width control with a .47mfd?"
When I recapped the set I used exact-value replacements. The width coil now has good range and the raster fills the tube mask at about half travel.

"Have you adjusted the horizontal drive?"
I made an attempt to, as the directions say to use that first to adjust the linearity, mainly for the outer portions of the raster.

I'll tackle the shadow first, and report back on the results. Thanks!

[Penthode]

I have repaired/ restored a number of TVs over the years. If the set is more than twenty years old, I make a habit of checking alignment. I generally find that even changing tubes is enough to change the IF alignment noticably.

With practice, IF and RF alignment becomes very straightforward and does not take long to perform. I recently went through the alignment of my RCA 9TC275 in about two hours. And like other aspects of this hobby, it is fun!

The interesting thing is that prior to alignment, the picture and sound on the set was pretty good. However after alignment the picture was noticably better and the audio was louder and clearer. I have attached some snapshots of the RCA's IF response (full IF and the overcoupled transformer between the tuner and 1st IF stage) and the 21.25MHz sound discriminator. The full IF has markers at the adjacent channel video (19.75MHz), sound carrier (21.25MHz), 22.1MHz, 25MHz, video carrier (25.75MHz) and adjacent channel sound (27.25MHz). Note that the KCS29 chassis has two adjacent video, two adjacent sound and two sound traps in the video IF strip.

I particularly like the earlier sets (prior to 1953) because many sets then had four IF stages. The four IF stages were needed to get the four MHz bandwidth. After color was introduced, three or even two stages were the norm which limited bandwidth to 3MHz or less.

My opinion is that in the earlier days, the loss of bandwidth was not too noticable because broadcasters, especially remotely located network affiliates, were hard put trying to provide 4MHz on network programming. However today, with excellent quality DVDs and downconverted HD broadcast, the NTSC quality has never been so consistently good. The early four MHz sets can display the extra quality now to good advantage.

[earlyfilm]

This applies only to B&W sets with focus coils:

Once you have repaired a few sets of this era, the below will be done automatically, without even thinking. For a first-timer with a knowledge of electronics from a different era, or from a different medium, it is very easy to mess up in these adjustments.

General instructions for eliminating neck shadows (round shadows on edge of the image) for post WWII through 1950's Black and White TV's with a chassis mounted CRT that have a focus coil. This also is useful for cabinet mounted CRTs with focus coils where the yoke must be removed for any reason. (If any of this contradicts the manufacturer's instructions, ignore that part.)

Since the CRT is usually secured by padded clamps on the edge of the faceplate and this padding may well have shrunken over the years, when you turn the chassis on its side to work on it, there is the possibility for the CRT to shift slightly. This can shift the yoke and focus coil alignment.

When you turn the set back right side up, before doing any centering adjustments, try to wiggling the neck of the CRT to see if there is any play. This also helps to reseat everything in back in its normal operating position.

The yoke generally should lightly touch the CRT bell -- I like to have them just loose enough to slide a scrap of waxed paper between the yoke and bell. This lessens the chance of the yoke sticking. Most focus coil sets have some slotted screw hole adjustment on the mounting bracket or support to position the yoke assembly.

As a rule of the thumb, the further away from the screen the yoke is on the CRT neck, the greater the chance of neck shadows.

First, adjust the ion trap for maximum brightness.

On sets where the centering is done with the focus coil, focus, but do not attempt centering until the horizontal (and to a lesser extent the vertical) linearity correctly adjusted as these interact. It is better to have the width and height slightly undersized if you cannot determine the correct width and height.

Use the centering adjustments (usually on the focus coil's mounting bracket) to center the image. Then gradually increase width while readjusting linearity to maintain a good image, again doing the horizontal before the vertical, until the image fills the screen without curved shadows that start in the corners.

The first time you work on a B&W TV with permanent magnet centering, you will be amazed how much that simplified this adjustment!

A few got-chas on ion traps:

Dual magnet: The black or darker magnet goes nearest to the tube socket. If there is a colored dot, usually blue, the dot goes away from the tube socket.

(Someone please double-check me on the above. It has been almost 50 years since I serviced a dual magnet set.)

If a single magnet, if maximum brightness either is completely off centered or usable brightness cannot be achieved, then the ion trap may be on flipped.

And the worst got-cha of all is on the very few CRT's that did not use an ion trap, where some well meaning person has installed one. If you don't have original service info, always look up the CRT in question!

Also during the B&W focus coil era, permanent magnets were not as permanent as we have today and sometimes the ion traps had to be replaced when they were only a few years old.

If while servicing, the set must be run for more than a few minutes with the ion trap incorrect, keep the brightness very low to avoid brownish burns on the CRT.

[old_tv_nut]

Originally Posted by ChrisW6ATV

Yes, high-resolution B&W sets will show the chroma as various patterns of dots, and the solution is to use the Y signal from an S-video or component-video output of a DVD player or digital-TV tuner into a modulator. Once color TV hit in the mid-50s, I think they just started making all the sets with lower bandwidth in general, but I may be wrong. A notch filter on 3.58 MHz would have helped, but I don't know if they were used in B&W sets later or not.

There never was a specific dot filter in a B&W chassis - unnecessary expense.
Also, manufacturers learned that a picture with less than full resolution, but reduced noise, was preferable to many people. The classic flat-topped response was replaced by a "haystack" IF curve, which attenuated high frequency noise and added mid-frequency peaking to restore apparent picture sharpness.