Good to hear this is coming along, considering my break from early color 21-fun (till I'm driven indoors by cold) I have nothing new to report.

A video posted by Shang066 https://www.youtube.com/watch?v=caS-GKl19KA highlights the desirability of an RCA CTC16XL and how its easier to diagnose than a Zenith 24NC31, which will requires advanced troubleshooting!~

For my CTC20, a few issues remain including focus taking a few minutes to dial in, sound issue due to PC board connection, it did take a replacement of all the electrolytics to fix the pesky sync issue.

Good to hear this is coming along, considering my break from early color 21-fun (till I'm driven indoors by cold) I have nothing new to report.

A video posted by Shang066 https://www.youtube.com/watch?v=caS-GKl19KA highlights the desirability of an RCA CTC16XL and how its easier to diagnose than a Zenith 24NC31, which will requires advanced troubleshooting!~

For my CTC20, a few issues remain including focus taking a few minutes to dial in, sound issue due to PC board connection, it did take a replacement of all the electrolytics to fix the pesky sync issue.

I always had the opposite experience from Shango. When I get an unrestored Zenith it typically works for the most part as is and just needs a few caps changed and some tweaking to work good.

Most RCAs I've encountered have had bad grounds, burnt jumpers, bad sockets, bad boost rectifiers, burnt flyback tires and various other issues that have to be found by troubleshooting.

Zenith tvs were some of the best.

had a rather lucky mistake at work this week, of the many hundreds of PCBS built, they put the wrong parts on some, rather than a high power NPN transistor, they put a dual diode in, THIS one , https://www.mouser.com/datasheet/2/308/1/MBR40L60CT_D-2315355.pdf.
sice it was powered on and thus removed, it Can't be used in the correct location, and thus MUST be scrapped, and so I nabbed one from the scrap pile, as it seemed to be perfect for a horizontal phase detector when i should ever need one.

It's NOT damaged, Just can't be used as a " new virgin " part.

:D:banana:

did a convergence tweak today.

https://www.youtube.com/watch?v=I5jhol_pSRo

can never et the top R/G vert 100%, and the upper right corner has always been dicey, but the rest is VERY good!
https://i.imgur.com/Oza4xm3.jpg


I think i need new caps in my pattern generator...

vertical linearity is also a bit off :(

Vertical linearity errors can affect the convergence at the top or bottom. I think you will "converge" on better performance bit by bit.
:yes:

Vertical linearity errors can affect the convergence at the top or bottom. I think you will "converge" on better performance bit by bit.
:yes:

Yes, I can see how it can, as its fed directly off the cathode of the Vert output via a cap resistor network, (50uf/5.6k) , but I MAY have screwed the pooch a bit here, :(, I did not replace c4 with an exact 50uf 150v cap like as listed, but with a 56uf 200v.
Will that 6uf throw things off that much?

Yes, I can see how it can, as its fed directly off the cathode of the Vert output via a cap resistor network, (50uf/5.6k) , but I MAY have screwed the pooch a bit here, :(, I did not replace c4 with an exact 50uf 150v cap like as listed, but with a 56uf 200v.
Will that 6uf throw things off that much?

My guess is it's not critical because it's not in the feedback loop for the vertical circuit.
Edit: besides, electrolytic tolerance is so wide it would never be designed into a spot that could have a large influence. It generally just needs to be big enough.

My guess is it's not critical because it's not in the feedback loop for the vertical circuit.
Edit: besides, electrolytic tolerance is so wide it would never be designed into a spot that could have a large influence. It generally just needs to be big enough.

but it does go down (pt 51) to pin 2 on the convergence assy plug, which goes directly to r27 R-G vert lines top, I have always wondered if that 56uf cap was a mistake. :(

but it does go down (pt 51) to pin 2 on the convergence assy plug, which goes directly to r27 R-G vert lines top, I have always wondered if that 56uf cap was a mistake. :(

Again, I think its only job is to be big enough. If you have a spare 50 microfarad of the right voltage rating, you could tack it across C4 to see if even doubling the value does anything.

If I'm following the circuit correctly, the total resistive load on C4 is about 100 ohms. This corresponds to a cutoff frequency of about 32 Hz, which should be good to carry the 60 Hz sawtooth shown on pin 2 of the convergence connector. Increasing C4 should only make it work better.

I tweaked the vertical linearity and it mad a minor dif at the top, right top corner is still worst, may never get that perfect.

THIS time I know the placement of the neck parts are right, as i used the GE CTC-15 clone as guide.
https://i.imgur.com/jN1Qj1g.jpg
CTC-16

https://i.imgur.com/kjHeZ2J.jpg

clone

convergence yoke just inside the black area, purity magnets, red area, blue lat, just beyond that.

I may play with it more this weekend, but i NEVER did replace ALL the resistors on the convergence PCB, caps, the selenium device, but not all resistors, and they DO get hammered, this may be a source of trouble..

Just a note: on my CTC-5 adjusting the V lin could not get it there, but replacing the vertical tubes improved the linearity a little bit and the top convergence quite a bit. No guarantees, but new tubes may be worth a try.

Just a note: on my CTC-5 adjusting the V lin could not get it there, but replacing the vertical tubes improved the linearity a little bit and the top convergence quite a bit. No guarantees, but new tubes may be worth a try.

easy enough to try, its only 1 tube 6GF7A found a NOS for $$9.75.

unlike the HOT, which the audiophiles have driven up to insane prices... :tears:

While I wait for the NOS 6GF7A to come, next week, or so the tracking says, I have decided to re build the convergence PCB (again), THIS TIME, making sure to replace all resistors that were not replaced before with 5% metal film, and all caps with 5% Panasonic, not sure what caps are in there now, this SHOULD make some dif, I hope, not sure why I skipped the 100 ohm & 180 ohm resisters last time.
Over all cost, $13, costing more for shipping 250 miles from Mouser than the parts, nothing new, but they get here in a day most of the time!

And shipped.
that's one of the good things about being so close to Mouser, always next day service!

So there will soon be all new parts on the Convergence PCB aside from the coils and Pots.

new parts are.
ECG120 Color TV Convergence Rectifier (on PCB,got in 2019)

ECQ-E6823JF3
ECQ-E2563KFB
ECQ-E2104JF
ECW-FD2W124JQ
PR01000101000JR500 x3
PR01000101800JR500
PR01000102700JR500

No clue if this will make any difference at all, but you never know.

Definitely a Resistor problem :yes: don't know WHY i did not change them when I put the diode pack and other caps in :eek:

did a quick check while i had nothing better to do.

1 of the 100 ohms checked at 106 (passable) another at 205 FAIL HARD!!
will wait till Friday night to rebuild the PCB, and the start the convergence process all over again, cause no doubt this will change everything.

If i had $1 for every time i have done the convergence process, I'd be a millionaire! :P

I really am curious just how much an overall effect this 1 bad resistor can really have.
https://i.imgur.com/exgm9RR.jpg
I know it all interacts with each other, but will that 1 bad resistor being over 100% off cause the center to be off ( static convergence) by being so far off?
I'm very eager to see how much it's going to change.
R220 was within tolerance, as was R218& R217, could not test R219 in circuit, as they are across coils.

The diodes are meant to keep the center adjustment constant when adjusting left or right, but I don't know how much that is affected when R221 and R220 are so imbalanced. Guess you will find out.

You could test this before you replace R221 - does the center remain constant when you adjust R25 and R28?

The diodes are meant to keep the center adjustment constant when adjusting left or right, but I don't know how much that is affected when R221 and R220 are so imbalanced. Guess you will find out.

You could test this before you replace R221 - does the center remain constant when you adjust R25 and R28?

It always has to some degree if I remember, in fact, SAMs has doing static convergence a 2nd time in the procedure.
So I guess it WILL be changed by quite a bit!
I'm in for a fun night Friday! :)
SAMs steps.

static convergence
R-G Vert lines top
R-G Vert lines bottom
R-G Horz lines top
R-G Horz lines bottom
Blue Horz lines top
Blue Horz lines bottom
static convergence a 2nd
Blue Horz lines right
Blue Horz lines left
R-G Vert lines right
R-G Horz lines right
R-G Vert lines left
R-G Horz lines left
go crazy because you have just spent 2+ hours on this going round and round and you have a headache from looking directly at the the screen 3 inches away from your face because your glasses cause chromatic aberration making it even harder to get the silly thing set right! T_T

Got the new parts today as expected, and it never ceases to amaze me how much resistors have advanced since the 60s, I mean they ARE 1w but they are ¼ the size of what they are replacing, and will most likely last much longer!

WOW, just wow!

"¼ the size of what they are replacing, and will most likely last much longer!"

Also, a certain bridge to Brooklyn is 1/4 the size it used to be, but carries as much traffic.

If they are that much smaller, they will run that much hotter. Its the laws of physics.

Because they are hotter they may well not last any longer than the old ones.

But worse ... being hotter, they are more likely to damage other parts close to them.
You need to space the new ones out so that they are centered exactly where the old
one was. Even then the spot directly above them gets hotter.

In general, if an old resistor is rated more than 1/2 watt, I make sure the new one
is roughly the same size, even if much higher rated. If the old one was 1/2 watt,
I just check and make sure the new one is running at less than 1/3 its rating, and is long enough to take the peak voltage across it. Of course lots of old 1/2 watt carbon resistors were run at far less than 1/2 watt.

https://www.mouser.com/datasheet/2/427/pr010203-1762580.pdf

It's unlikely that heat will be an issue with these at all, I chose “power resistors” vs standard ones, and the rated voltage @ 350 is far beyond the original carbon composites, and even if they do run a bit warmer, they are going to be mounted raised a bit & not flush like the old ones were.

Another thing to keep in mind, the newer ones are much better in dissipating heat than the old carbon composite resistors, and thus are substantially smaller.
I can't find by what factor exactly they have improved, but it seems by being made of better materials, IE glass/ ceramic cores vs doped carbon, and thinner insulation ETC, what physical size resistors that were approximately 1W now are 3w, so on and so forth, this is how they have progressed things.

i put in one new resistor , the one that was worst off, just to see what difference it would make.
https://i.imgur.com/joQpdzx.jpg


and you can see on the thermal scan how much cooler it runs vs the old carbon ones.

also it DID change the center.
https://i.imgur.com/S6HMTfL.jpg

Parts on the convergence PCB changed, the new resistors do run cooler than the old, things made an over all improvement but STILL having a hard time with RG vert top.
Having to adjust R27 to the extreme to get it close, leaving R217 out completely gets it even closer.

All this has made a 15% improvement, parts on the convergence PCB & 6GF7A.
Will mot likely add replacing that C4 with a exact 50uf cap when I ever have the chassis out next and see what does, but done working with it till next time, there is ALWAYS a next time! :O

https://www.youtube.com/watch?v=cURROx6hcv0

all room heaters on at once!

At this point, I think I would try sliding the convergence coils forward and backward a little to see if they are not exactly over the internal pole pieces. It should not be necessary to run R27 to one end. Are any other controls way off center?

R27 is the only one acting that way, and has been ever since the set was gotten working again.

Thus I have been suspecting the 56uf on place of the 50uf at C4 for some time now, I'm not even sure of the status of R106 which is under the PCB, this may be sending a wave slightly too big/small to that circuit on the convergence PCB making it ALMOST in range.


Obviously the 2 resistors from the cathode of the vert output to ground are OK R127/R126 ( also tied to pin 8 of HOT ) as there is no problems with sweep.

https://www.youtube.com/watch?v=XfnvND-Kb5Q

video test after latest convergence

RF input

https://www.youtube.com/watch?v=XfnvND-Kb5Q

video test after latest convergence

RF input

Looks great!

Yes, still working rather well via tuner, given that I got it after a mad tweaker got done with it and lost the cover to the IF section, removed the color PCB and did unspeakable things to it like replacing the color takeoff and bandpass coils when it was not really needed. :/

It's working real well with LD video and unlocked DVDs, but as usual for sets of this era, trying to use a cable box via the tuner ends up in buzz-O-matic city, so rather than trying to readjust the audio section to any given channel I'm trying to watch via cable, I just hit the bypass switch and go direct A/V input.

but it's good to hook up the rf modulator once in a while to see that the tuner / IF is still happy and healthy! :D

On a completely unrelated note, ( to my 16XL) anyway, I now know with relative certainty what was wrong with the Roundie of my childhood , the RCA, CTC-10A "The Sullivan" from our grandparents that my dad gave up on trying to fix and just got rid of.
Although I was very young at the time, I was always watching him trying to work on it and remember exactly the symptoms it had, it would work fine when first turned on, good picture, good color, nice and stable, but as it warmed up it got unstable, jittery.

He spent weeks/ months playing with it before he gave up, replacing tubes, resistors, capacitor NOT electrolytic filers though.

But the one thing this IBM engineer overlooked, and was most likely the fault, the selenium horizontal phase detector.

What a waste...
I wish I had a pu truck and a flux capacitor right about now.