Need help with a CTC-15 vertical problem!

[Turle]

I’m working on a ctc-15. Everything was going smoothly until I noticed that I can’t adjust the height at all. The picture looks squashed. The height pot is good. All the resistors in the circuit are good, I checked all of the capacitors. Swapped out the vertical output tube and nothing. The grid of the vertical output wants 30 volts, but jumps around between 3 and 5, adjusting the control only changes it by half a volt or so.

Would anyone know what could be causing this problem? I’ve been stuck on it for days now

[Yamamaya42]

you are sure that the convergence PCB is plugged in and working correctly, cause if is not plugged in and working, it wont get the right load/ feedback and you will only get half sweep.

[reeferman]

I know you said you checked the caps, but if it's pulling up from the bottom sub the 50 mike on pin 3 of the output.
It fixed a lot of them 50+ years ago.
But then again that was 50+ years ago.

[zeno]

If the pix has good lin & caps are fresh its usually one of the
high ohm resistors feeding the height control. You have to
lift one end to properly measure them.

73 Zeno
LFOD !

[Yamamaya42]

Originally Posted by reeferman

I know you said you checked the caps, but if it's pulling up from the bottom sub the 50 mike on pin 3 of the output.
It fixed a lot of them 50+ years ago.
But then again that was 50+ years ago.

And is part of the feedback loop mentioned above, the 50uf cap & 5.6k resistor on the cathode is tied to pin 2 of the socket of the convergence assembly, found out the hard way that weird stuff happens when not plugged in and loaded correctly!

[old_coot88]

Most common cause is the electrolytic coming off the cathode of the vert output. Plate load resistor of the vert oscillator often goes 'waay off spec (high) due to being hammered by high level spike.

[Turle]

Originally Posted by Yamamaya42

And is part of the feedback loop mentioned above, the 50uf cap & 5.6k resistor on the cathode is tied to pin 2 of the socket of the convergence assembly, found out the hard way that weird stuff happens when not plugged in and loaded correctly!

3FDB6951-A264-4CC1-9BC1-67A2A281A48D.jpeg

This is not a widescreen program. The linearity looks fine. There is just not enough deflection

[Yamamaya42]

Originally Posted by Turle

Attachment 206077

This is not a widescreen program. The linearity looks fine. There is just not enough deflection

read through this thread, and what he had to do to get full screen back :O
http://videokarma.org/showthread.php?t=271514&page=5

on MINE, a CTC-16xl i had to replace what is R105 & R106 on your CTC-15, the resistors on each side of the height pot, they were way off on mine.

[old_coot88]

You indicate all resistors check good. But double-check R104. It's a 2.2 meg half-watt, going to pin 8 of the 6GF7. It's the plate load resistor of the vert osc. https://www.earlytelevision.org/pdf/...ams_0673-2.pdf

[Turle]

Originally Posted by old_coot88

You indicate all resistors check good. But double-check R104. It's a 2.2 meg half-watt, going to pin 8 of the 6GF7. It's the plate load resistor of the vert osc. https://www.earlytelevision.org/pdf/...ams_0673-2.pdf

It’s measuring about 2.5, I figured it was close enough to being within tolerance that it wasn’t causing the issue

[old_coot88]

Originally Posted by Turle

It’s measuring about 2.5, I figured it was close enough to being within tolerance that it wasn’t causing the issue

Yep. Scratch that one off. A good thing to bookmark though. It's a frequent failure point in designs that run the vert osc from B Boost (not just RCA)

[Yamamaya42]

If you have checked all the resistors involved, and know that they are OK, and same with all the caps that could be causing the issue, cause they often can be a bit sneaky and leak at operational voltage, and hard to really test unless you have a tester that will push it to it's limits like the vintage cap testers would, but if you are sure the caps are good, and the boost voltage is within the correct range, one thing to try is a resistance test of the vertical winding of the yoke, YEL & YEL-BLK terminals, should be about 23.5 ohms.

[Turle]

Originally Posted by Yamamaya42

If you have checked all the resistors involved, and know that they are OK, and same with all the caps that could be causing the issue, cause they often can be a bit sneaky and leak at operational voltage, and hard to really test unless you have a tester that will push it to it's limits like the vintage cap testers would, but if you are sure the caps are good, and the boost voltage is within the correct range, one thing to try is a resistance test of the vertical winding of the yoke, YEL & YEL-BLK terminals, should be about 23.5 ohms.

Turns out it was the 150k between the height and linearity pot. Looked fine in circuit but pulling it out showed that it was measuring over a Meg. I replaced it and the height works fine now

[Yamamaya42]

Originally Posted by Turle

Turns out it was the 150k between the height and linearity pot. Looked fine in circuit but pulling it out showed that it was measuring over a Meg. I replaced it and the height works fine now

Glad to hear it!
That seems to be a common fault, cause as mentioned, it was also just as bad in my set.

[kvflyer]

Originally Posted by Turle

Turns out it was the 150k between the height and linearity pot. Looked fine in circuit but pulling it out showed that it was measuring over a Meg. I replaced it and the height works fine now

Another congratulations that you found it. Gosh, sometimes we just have to scratch our head!