admiral 24c15 with 20b1 chassis attempt at restore

[fumplet]

decided not to mess with it. especially on recommendation of not to mess with yoke caps/resistors. Must be some kind of resonant circuit. Anyway tv seems to be vertically jumpy like somebodys messing with height knob, twitches to slightly smaller height picctures....after a while goes away. Will get short video next time I fire it up.

[bandersen]

No, it's not a resonant circuit. It's just not worth risking damaging the yoke. If the resistors or cap are slightly out of spec, it's really not going to make any noticeable difference. If they had failed and you had ringing, it would be very noticeable on the screen.

[fumplet]

very interesting. almost makes me want to get that sencore ring tester you have. Not sure how useful the sencore ring tester is.

[bandersen]

A Ring tester detects is a yoke or flyback is open or has shorts. If you had either, it would be very apparent on the screen.

If you have horizontal ringing, you will see vertical bands on the left.

[fumplet]

And if those bands can be adjusted out then no bad yoke or flyback?

[old_tv_nut]

The pictures from Banderson show a non-failed, working yoke and flyback. This kind of ringing is a more subtle problem, not an out-and-out failure, and not an indication that it's about to fail either. A set can run forever with this kind of subtle flaw.

I don't have the experience to tell you what remedies to try for this, but it's not fatal.

[Penthode]

I see there mention of the little high voltage ceramic or mica capacitor across the left side of the horizontal deflection windings of the yoke. I believe it is to balance the distributed capacity but also I think it helps "tune" the left hand side yoke to prevent these ripples.

Typically it is valued between 47pF to roughly 120pF. I recall they were often selected on test and weren't even assigned an exact value.

You might try experimenting slightly raising and lowering this capacitor value within the range above to see if there is any improvement.

Come to think of it, is the capacitor present?

Also while you are at it, you might confirm the 560 ohm vertical winding damper resistors are still good.

[bandersen]

I don't believe he has any ringing issues so no need.
I was just showing him examples of what it looks like.

As far as I know, the remaining issue is the image being slightly off center.
I believe it is either because of physical adjustments being off or horizontal non-linearity where the image is slightly compressed on the left and stretched on the right.

[bandersen]

Here's a recent image to remind us of the issues.
Image is being pulled up to the left.

[fumplet]

https://www.youtube.com/shorts/oIu4j7k1Qy8
The jumpy goes away after a while for the most part. I hope I didnt damage the yoke while trying to make sure it was tight against the crt. STill hunting for picture centering issue. I chickened out again taking the tube out. Probably this weekend when Im not pressed for time with help.
Tried again tonight j(friday), with help and I cannot get the crt tube socket through the yoke. Does it require a good bit of force or will that damage the yoke? Am I supposed to take off the focus coil first? Or just give up. Only thing I did was scrub the area around the high voltage part of the crt with wire removed.
TUNER is still dirty thats why the sound kept on going in and out. I can grab the main click knob and rotate counter clockwise and sound gets louder but IM stuck holding the knob slightly off click for louder sound. Im assuming that means dirty tuner. Even the contacts as seen through the side of the tuner look black/tarnished. Im using radio shack contact cleaner and lubricant. Says for tv tuners. Is there anything better?

[Penthode]

Originally Posted by bandersen

I don't believe he has any ringing issues so no need.
I was just showing him examples of what it looks like.

As far as I know, the remaining issue is the image being slightly off center.
I believe it is either because of physical adjustments being off or horizontal non-linearity where the image is slightly compressed on the left and stretched on the right.

Yes focus coil position or an unwanted dc current through the horizontal deflection coils.

I still see the dark vertical bands on the left which could be due to a ringing in the first half of the sweep (inefficient horizontal damping?) or the damped flyback somehow modulating the video (poor power supply decoupling or filtering). This is something an oscilloscope would see.

Is the focus coil hole perfectly centered around the neck of the tube? Are the horizontal deflection coils capacitively coupled to the horizontal output transformer? If so a leaky capacitor would shift the image.

[fumplet]

Focus coil is and isnt perfectly centered around tube neck depending on what im messing with. Trying to adjust yoke on tube and or taking tube out but cant due to tube socket getting stuck in yoke. Focus coil is slightly tilted horizontally but its tilted in the direction of which I want the picture to go or move I think but that could be just the yokes cap next to the focus coil causing the illusion of being tilted. Well if it is a leaky cap then it would have to be a mica one unless i have missed a paper cap. I have not removed the rectangular shield under chassis yet so if caps are hiding under there i will look. Notice the disc caps which have wax on them and they appear to be bubbly under the removed cover. Disc caps getting hot from going bad which everyone says they dont go bad hardly at all or is this ambient heat absorption. The heat baked 15k resistor measures 7.5k ohms so somethings parallel with it or it needs replaced. Also, under the video cover theres like 4 or 5 of 1k ohm resistors that are 1.2k and above in value with highest at 1.5k ohms. The Canohm resistor I suspect is also not too good and guessing this is the 6k ohm resistor and IM getting readings of 6.3k up to 35k ohms.
.

[bandersen]

Originally Posted by Penthode

I still see the dark vertical bands on the left which could be due to a ringing in the first half of the sweep (inefficient horizontal damping?) or the damped flyback somehow modulating the video (poor power supply decoupling or filtering). This is something an oscilloscope would see.

I'm not seeing any dark vertical bands at all. Are you referring to the test pattern image a few posts above?

Sure looks to me that there is sufficient width and the squares on the far right are not quite as wide as those on the far left.
That's why I keep saying it's a linearity issue and you need to adjust the drive/linearity/width controls.

Don't mess with anything under that metal shield. Those parts have nothing to do with centering the image.

Also, why are you trying to get the picture tube out?

[fumplet]

trying to get picture tube out just to see how the yoke looks and possably if there was something keeping yoke from laying flat against tube. I did move the picture tube stand around a bit and it does have a small affect on the picture left or right. Not tons of adjustment but a small amount.
According to the tuner diagram, the contact strip of tuner is held in by two screws, can I remove this to clean that strip or is that asking for trouble?
While watching it play seems sound still goes in and out sometimes and sometimes I can adjust the 1st audio transformer and get it to come back louder or just better. Well, this time focus went totally away as well as sound for a bit. its like sound slowly gets softer and can even slowly come back. Focus knob is now to one end of it for almost sweet spot. Focus coil is near straight and centered to the tube neck. Sound just faded out with focus again. Wait 10 minutes with it on and sound with focus comes back. voltage at the yellow wire focus rheostat is about 280 and when sound with focus goes out this voltage goes up to 340 volts, wait a while and it goes back on. NOt sure yet if the resistors I just replaced are the cause or not, r215 should be 6k and a can ohm riveted to the chassis.

[bandersen]

It's asking for trouble. Clean the exposed bumps on the tuner segments. The black is tarnished silver.

Here is what it looks like if you do open it up.