CTC-9 tint control oddness

[DaveWM]

I recently turned on my CTC-9 and noticed the tint control acting "funny"

it had a dead area in the middle that caused the CRT to have no color just a BW picture, rotate it toward purple and the color would come up slowly, like a control control, but no change in tint. rotate back thru the dead zone (about middle till the very end of CW) and you could get a bit of green tint control but very weak color and the fine tune had to be on the ragged edge.

I did not recall having this issue with the set in the past but it had not been on in months, so not sure if it was doing before.

Anyway the fix was in the color killer, I turned it CCW and all was fine. I did not bother to set it up at the time (no color snow on off channel) but will later.

Anyway it confused me the way it would only kill the color when the tint range was in the middle to nearly fully CW (green). I just assumed the Color killer would kill the color completely if not adjusted right. Perhaps it should and I have some defect in that circuit.

[ChrisW6ATV]

That is odd, but I have not adjusted enough color killers to have a good answer.

[DaveWM]

follow up, it does not kill the color any more (or even reduce it) when adj the tint now, BUT I was wrong about it working fine, it still lacks good range, the tint shift is slightly green to normal, but never over shoot to purple.

I tried subbing a new phase detector (6AL5) and chroma ref osc control/chroma osc (6GH8). no change. the set calls for a 6EA8 but it had a 6GH8, although I doubt that could be the problem. I did try a few other 6GH8's no change.

Its not like the range is just too green as the green shift is not that much either. I really am not motivate to pull the chassis so will prob just get some new 6EA8's to be sure its not a tube problem. Even checking the tint pot would require pulling the whole chassis.

[old_coot88]

OOPs! Double post

[old_coot88]

Have you DeOx'ed the tint pot?
If so, I would disconnect one end of the pot and check it with an analog ohmeter for smooth operation stop-to-stop.

[DaveWM]

OC I will def check out the tint pot, its just a bit of a pita right now as I have the set in a tight location.

[jr_tech]

The wiper of the killer pot connects to the killer circuit *and* phase detector circuit through a 10 meg resistor, which is bypassed to ground with a .047uf capacitor...perhaps the cap is leaky, or the resistor has changed value?
jr

[DaveWM]

I will note that and and check it when I pull the chassis. seems likely something is up with the color killer since it was acting odd as well.

[TV Engineer]

Have you done a color afc alignment? All that is needed is a VTVM and color signal, and it will reveal the cause of many problems in a malfunctioning receiver.

[DaveWM]

I have not, but I do have the VTVM and the Sams, so I can do that.

[oldtvman]

I had that problem on the set I just sold and it was nothing more than tweeking the agc control.

[Dave A]

I have a Philco Portacolor clone with the exact same problem. Someday....

[old_coot88]

Originally Posted by DaveWM

I presume you mean the 12AZ7 dual triode...

...what makes you think there is a demod problem?

Well, it seems like blue portions of the chroma information are suppressed or 'not there', hence not able to render purple in the flesh tones.

Meanwhile, luma information appears overly blue due to blue screen being set a tad high.

Have you set the grey scale (i.e., with color turned off, each gun extinguishes at exactly the same screen setting)?

Re. The Portacolor clone (if it's a GE clone), doesn't it use that uber-simple 'ringing burst' in lieu of a referance oscillator?

[DaveWM]

the grey scale seems fine, when I turn down the color I get a normal looking BW pic as I adjust the brightness up and down.

the video is not the best, seems to be messing up the blue (there are times when the screen looks predom blue and its not.

I will get a NTSC color bar signal on it to make sure its working properly.

[DaveWM]

https://www.youtube.com/watch?v=Yr_T0-Em0qQ

color bars showing lack of tint shift.

the plan next will be

exchange color output tubes just so see if there is any change, sub a new demod tube (uses a single dual triode for the X and Z) again just to see if any changes.

if no improvement, I will pull the chassis out some so I can get to the test points. The sams has me grounding the output from the chrroma band pass trans (not sure why, this is point N on the sams) then puttting a vtvm on one of the pins of the 6AL5 phase detecting diode and adjusting the 3.58mhz osc coil for max deflection, then adj the burst trans again for max deflection, lastly grounding point O (the ref voltage from the two matched resistors) and setting the reactance coil for color bars that are still or nearly still. (of course this is with the tint control set to the middle of the range) I have not done the max deflection setup part before so I will measure the coil settings before adj JIC I need to get back to where I am now.