Convergence ?
 

Is there any definitive reason why a perfect convergence is obtained but after a few months it goes out of where it was previously. Never moving the set. Or is this just 60s technology just not perfect.

Component drift. Most notably the selenium stack on the conv board if it's still original.

Yes the selenium is still in this set was going to change it but decided since the convergence was good I left it.

Dittos to Mr. Coot.
Diodes or cold joints on the conv board. I saw a few 14 & 16" Zeniths where
the blue IIRC would pop in & out, it was the conv yoke itself. The diode pkg
can be changed with a direct sub ( ETG etc.) , OEM or separate diodes.

73 Zeno:smoke:
LFOD !

The struggle for perfect convergence on these older sets is a NeverEnding Story.
No matter how perfect you get it, it will always S L O W L Y drift off over time due to several factors, first and foremost being the selenium rectifier pack mentioned, and/or slow changes in the resistors in the circuit wich are always under load, and not to mention repeated heating and cooling cycles of the convergence clover & magnets themselves.
Even the Earth's Les Chants Magnétiques ( magnetic fields) can have an effect to some degree as it changes.
But all in all, any shifts in convergence should be rather slow and subtle, perhaps needing a slight touch up every 2 years or so with light weekly use to keep the set at peak performance.

Yes that makes sense the convergence on my set is out very small in the extreme right side only on some scenes can bearly see it. I’m not even worried about it but yes magnetics is what the convergence works on.

Small changes in sweep scan probably effect it too, changes in line voltage and tube aging will effect the amplitude and linearity of the input waveforms which should change the output some.

My line voltage has big swings here 119-123 vac

A voltage regulating isolation transformer will fix that. I've got the same problem only worse as the industrial park near me will cause voltage to fluctuate rapidly causing blooming. Those transformers fixed that. I try to run my valuable early color sets on those transformers to protect them.

Don't forget the shadow mask also plays a factor.

This is true, but not so much due to the input waveforms affecting the output waveforms (which are heavily filtered to get the parabolas), but the fact that the distortions in the input waveforms are higher frequencies that do not carry through to the output. Thus, the spot is in the wrong position for the amount of convergence current when the linearity is bad.

? I didn't think the mask affects convergence, only purity. ?

It affects both. Minor warpage or magnetism will affect purity, severe warpage affects convergence and purity, but these tubes were very stout physically and it would take a significant impact to warp the shadow mask bad enough to affect convergence.

Later tubes were more prone from bumping, and just looking at a Trinitron crosseyed would give them fits.

John

And it's been over a year and a half, and i can tell it is time to touch up the convergence again on my CTC-16XL, ans it has drifted slightly and is not as sharp as i want it to be.

I guess every times it's tuned on/off (thermal cycle ) it drifts a tiny bit. :tears:

gonna wait for the next work holiday to do it however.

as always for me it's a hours long event going round and round with my face 2 inches from the screen, cause i can't use my glasses to do it cause of the chromatic aberration the lenses cause :(

Has the convergence diode pack ever been replaced?

Yop, with a NOS selenium rectifier pack

I never did like the sliding type of holders they used for the static magnets, always seemed problematic, you look at them funny they shift!

It's only slightly off gotta look close to see it, but not as good as it used to be.:tears:

my other roundie, the GE CTC-15 clone which is rarely used, is still pretty good, so I'm guessing it has to do with once a week use for an hour or 2 and thermal cycling, over the last year and a half.

I replaced the Vert tube June 22 with a NOS 6GF7A, that was the last time it was converged.

Perhaps the tube has broken in a bit, and things are slightly off now, who knows.
blue static is very slightly above R/G, and R/G are not as good as they could be.


R/G vert top is also a bit off again :/

Convergence can be affected by vertical height and linearity. I would check those first before touching the convergence controls.

Age brings inevitable change that can't be reversed.
Accept it and enjoy the picture.

That would no doubt be the first step I check, but i co have no doubt i will have to touch things up again.

If i have to spend a few hours with my face to the screen every year and a half to 2 years to keep it in peak convergence, i really don't mind it! :D:yes:

https://i.imgur.com/8wFk2gc.jpg

I know what the set can do!

About how many hours of actual operating time does that represent? :scratch2:

jr

This set gets occasional weekend use, mostly on Sat ( not every one ), from 30 min to an hour, and periods up to 2 hours or more on Christmas eve, there are of course other brief times that it's on, but those are the regular use it sees.

I've been fighting the comvergence on my 16X lately too. Some sets converge up nicely, while others fight you every step of the way. My 16X is the latter example. I replaced the recitfier block and it helped, but after 3 hours of going around and around, my back was aching and I got it "good enough."

I have gone thru this as well. Always wondered if it was the geometry of the shadow mask itself? Eg maybe it is slightly warped over time?

Same with my Motorola some days the convergence is good other days it’s alittle off as it may be static in the rug it sits on.

Mine has always been a fight as well, round and round to try and get it as best as I can, always seems worst on the right side :(

Shadow mask warping would ruin the purity long before affecting convergence. In fact, convergence is supposed to make the beams coincide at the faceplate, not at the shadow mask.

Long term drift most likely is due to circuit components, not only in the convergence circuits but in the horizontal and vertical size and linearity.

Of course, some sets just never will have all four corners optimum at the same time (and if you're really picky, maybe all sets).

Some time ago, thinkering and playing with my delta gun TV (a "last generation" delta-gun; the only delta in my small collection), I almost created a thread for the convergence issue, but then I found that the TV certainly dropped, and purity is not consistent also.
This affected one side; the left side converges scary unbelievably good, basically textbook perfect, but right side, the G is not || to the R+B (coincides with bad puruty)... this is strange; normaly I see people complaining about R or B not converging to the others... this G lost even don't make sense to the convergence panel adjustment descriptions.
So, I think I can need to live with it, until I found another set.

Or, is worth to try to play a little with it?

PS.: this tube also have another problem, but I think is about the socket: is very inconsistent with focus. But, I dunno why the image is more dim when focus is wrong, go figure... (well, I never worked with delta gun CRT, so I dunno if it is a normal behaviour, or...)

Besides Trinitron, I had a Samsung 32" widescreen that lost purity with a little impact... ouch... very sensitive it seems

There are things you can do. First thing I would try is using an external service degaussing coil to try and get the impurity to go away, then if it doesn't I would go through the purity adjustments and see if I could adjust it out. (Edge purity is highly dependent on deflection yoke position so doing a full by the book purity may fix it). If that doesn't fix purity maybe try a refrigerator magnet on the bell near the bad spot as a last ditch.

EDIT: to keep from going off topic others mentioned some sets are a pain to converge... I've found 2 things influence that bad convergence board parts (R,C and diodes), and convergence yoke placement and warping. Sometimes the yoke needs to be back or forward ~1/4" from where it's at to either have more range or overshot less, I've also seen some plastic yokes where one set of petals is angularly closer than it should be due to plastic degradation... That's not easy to deal with.
What probably gave me my worst headaches until I realized was a 19" metal cabinet Zenith a respondent to this thread sold me a while ago...I spent a bunch of time troubleshooting the board because of top hat diodes that looked like they'd been soldered in by Ray Charles, then finally realized that the convergence yoke was installed BACKWARDS and the red yoke petal was over the green gun and vice versa....It got really good when I fixed that.

The biggest question that I always had was exactly WHERE to place the parts on the neck of a 21fjp22(a), convergence clover, ETC, cause of the internal markings, you can't see where it goes like you can on later rectangular delta types, on which you can very easily see where to put it.

But I can never find a definitive answer for the rondies saying it goes, HERE!

SO, I have it placed exactly as it was on my GE CTC-15 clone set when I first got it, down to the mm. in placement.

So very true! With my 21AX, I did a lot of fiddling, looking for the position with maximum effect and then comparing with the un-dimensioned illustrations in the service literature, readjusting, round and round. The results I get for both purity and convergence on this rebuilt tube suggest to me that the replacement gun may be slightly rotated from nominal position.

Down to the mm is getting pretty serious!

Well, i took a ruler, and measured how far every part was on the clone was from the socket cap, and place that same distance on my RCA.

http://suzaku.live-evil.org/GE-ctc-15-clone.jpg

http://suzaku.live-evil.org/rca-ctc-16xl.jpg

that is assuming they were correct on the clone in the first place! :tears::D

My default is over the giant focus element that the 3guns go into at the end of the gun...some tubes leave it exposed, others you can peak under the dag , some have a red band and others you have to guess.

Perhaps +/- 0.25 inch would be adequate (for placement of neck convergence parts) :scratch2:

https://frank.pocnet.net/sheets/168/2/21CYP22.pdf

jr

As +/-0.25" is the range of adjustment, convergence can be within a few mm. on the edges and smack on in the center.

Great, thanks! So there is some hope.

Too bad, the service for this model have the complete setup only for the in-line CRT (at least indicates the preferred sequence for the convergence board adjustments), so I need to apply/use the "generic" delta gun alignment then... What is the most preferred documentation for learning that (if extra degaussing not solve the problem)?

About EDIT: inspired by the simple "Convergence?" thread title, I ended posting about it just here... ;-) but if moderators prefer to change this postings to a independent thread, I'm also happy :-)

So, I guess I will try and touch it up this Sat, gonna have to get to it soon anyway as one of the fans I have on the back is starting to make noise and has to be lubed, most likely due to the cold.

So I'll assume the parts on the neck are correct for now.
As mentioned, the biggest pain I have with it is the nonlinearity of the R/G horz lines on the right side, always been a pain on this set. :(

As suggested, gonna start with vertical height and linearity, and perhaps vertical and horizontal centering if needed, before going to convergence, however my test generator has no output to do height and linearity, I do have the Digital Video Essentials DVD, and hidden deep in a horrid to navigate menu system is the right tools and screens to do so, it's just a nightmare to find it!