My CTC-16XL Project. - Page 34 - Videokarma.org TV - Video

Yamamaya42 · #**496** 02-21-2021, 10:16 PM

with them side by side now, i can really see the difference between the 21fjp22 and the 21fjp22A.

In the greens mostly. but I;m not sure if that is just a difference in the color/ video circuits of the CTC-15/GE and the 16XL.

Yamamaya42 · #**497** 03-03-2021, 10:06 AM

About the focus circuit, I have seen it said that the 66meg (6kv) resistor gets hammered a lot and often drifts out of spec, I saw this in the GE-CTC-15 clone, but what about the 130pf ceramic cap? Are they pretty stable, or need attention also sometimes?

Electronic M · #**498** 03-04-2021, 02:37 PM

I've read a case or 2 of that ceramic cap going open-ish (not producing a good null on the eye tube of a restored 60's cap tester). But on average they are pretty reliable.

Yamamaya42 · #**499** 03-04-2021, 03:11 PM

Then I don't think its bad in my 16xl, but I'm sure the resistor is worn, not that I CAN'T bring it into focus, but in order to do so, I'm almost at the limit of travel on the focus coil, so it can use a new one I'm sure.

Just another thing to add to the list next time I take it apart.

Yamamaya42 · #**500** 09-28-2021, 02:20 PM

So far, my CTC-16XL has been going very well with hourly weekend usage, no major problems seen yet, other then the minor annoyances mentioned before.

So, until something pops up to urge me to pull it apart, I wont sweat the small stuff, but I may touch up convergence, it's a bit off again.
As stated before, on the list of minor stuff.

Replace the 66m focus resistor that seems to have drifted a bit.

Restore the grounding of the delay line to factory spec & put in new peaking coil to replace damaged one, ( though it may be OK, never hurts )

Replace resistors and cap on plate of video output, that gives vertical blanking. ( missed them when I restored it. )

That's about it.

DavGoodlin · #**501** 09-29-2021, 09:04 AM

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.

Electronic M · #**502** 09-29-2021, 07:09 PM

Quote:

Originally Posted by DavGoodlin

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.

consoleguy67 · #**503** 09-30-2021, 06:56 AM

Zenith tvs were some of the best.

Yamamaya42 · #**504** 10-28-2021, 10:59 PM

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/2/3..._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.

Yamamaya42 · #**505** 06-04-2022, 08:30 PM

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

old_tv_nut · #**506** 06-04-2022, 11:33 PM

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

Yamamaya42 · #**507** 06-06-2022, 02:01 PM

Quote:

Originally Posted by old_tv_nut

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

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?

old_tv_nut · #**508** 06-06-2022, 02:29 PM

Quote:

Originally Posted by Yamamaya42

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.

Yamamaya42 · #**509** 06-06-2022, 02:42 PM

Quote:

Originally Posted by old_tv_nut

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.

old_tv_nut · #**510** 06-06-2022, 04:41 PM

Quote:

Originally Posted by Yamamaya42

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.