CTC-4 Director 21

[SwizzyMan]

I replaced the CRT with a 21FB that is a bit stronger. It displays a beautiful picture with all colors strong except for red which is weak. This has do to a problem with the circuitry driving the red cathode. I have been tracing back through the circuit and have been finding resistors that have gone off. I think I will tackle this problem before I continue on the color sync issue.

[SwizzyMan]

Im starting to really think the replacement crystal may be bad since it does have a big dent in the side of it (Must have occurred during shipping) and I cant seem to get the color to lock no matter what I do. With the last crystal I could get the color to lock I believe. I will swap the crystal once I can find one. Work has been slow this whole year and I admit I have been lazy with the restoration of this set and have not worked on it as much as I should have. Summer is coming up soon so I hope to have the set finished by August. Slowly but surely this set is shaping up!

[old_tv_nut]

They're cheap - get one or a few
http://www.newark.com/raltron/a-3-57...49u/dp/96F2798

[SwizzyMan]

Cant go wrong at 58 cents. Ill pick one up soon and go from there. I now have a whole lot of time to work on the set now. I hope to get it wrapped up by august.

[SwizzyMan]

New crystal is in and I can see a bit of improvement. Still cant get color to lock. But I can faintly see color through the rolling bars. Black and white picture is perfect I just cant get this pesky color to lock. I have tried putting caps across the crystal but I cant seem to get the frequency below 3.57900 (with a cap across the crystal). Reading through Phil's article on his 4 reveals that a 100pf cap can be put across L142 I believe. This TV wants to produce color, it is so close! Should I add a cap across L142?

[old_tv_nut]

Originally Posted by SwizzyMan

... I have tried putting caps across the crystal but I cant seem to get the frequency below 3.57900 (with a cap across the crystal)...

Did you mistype the frequency? 3.57900 is too low - should be 3.579545.

Edit: oops - I see you meant 3.57966 - still high.

[SwizzyMan]

Originally Posted by old_tv_nut

Did you mistype the frequency? 3.57900 is too low - should be 3.579545.

Edit: oops - I see you meant 3.57966 - still high.

Yes right, my bad. I can get it down from 3.57966 to 3.57900 with a cap across the crystal.

[old_tv_nut]

More C across L142 is easy and worth a try, I think.

[old_tv_nut]

What size cap across the crystal? It's probably too big if it pulls it 545 Hz too low. It needs to free run close to correct so the reactance tube and coil can pull it either way.

[SwizzyMan]

Originally Posted by old_tv_nut

What size cap across the crystal? It's probably too big if it pulls it 545 Hz too low. It needs to free run close to correct so the reactance tube and coil can pull it either way.

I seem to be mixing up my results here. What I get with the crystal across the cap is 3.5760. The target is 3.57545. I am not putting the right results here. Let me start over now. The closest I can get the oscillator to run at is 3.5766 without a cap across crystal. With a cap across the crystal I pull about 3.5762 or thereabouts. the capacitor across the crystal does not pull down the frequency much at all. I would venture to guess the cap was maybe 5pf.

[old_tv_nut]

I don't have the alignment procedure, but I imagine at some point you are instructed to tune the reactance coil for zero beat. If you can't make free-running frequency correct, the reactance circuit has little chance to pull it in.

[old_tv_nut]

Are you getting tired? You seem to be missing a 9 this time. I think this time the numbers you meant to type were something like:
crystal across cap: 3.57960
target: 3.579545
without a cap: 3.57966

If that's right, the cap is pulling it 60 Hz, which is a nice amount of pull, so it seems something else is wrong. Which capacitors in the reactance tube section and the 3.58 MHz oscillator have you NOT replaced? Do you know for sure the reactance tube is good? Is the plate voltage 5 volts lower than the B+ supply as the schematic says? Time to look for anything that is not right.

[SwizzyMan]

Originally Posted by old_tv_nut

Are you getting tired? You seem to be missing a 9 this time. I think this time the numbers you meant to type were something like:
crystal across cap: 3.57960
target: 3.579545
without a cap: 3.57966

If that's right, the cap is pulling it 60 Hz, which is a nice amount of pull, so it seems something else is wrong. Which capacitors in the reactance tube section and the 3.58 MHz oscillator have you NOT replaced? Do you know for sure the reactance tube is good? Is the plate voltage 5 volts lower than the B+ supply as the schematic says? Time to look for anything that is not right.

Yeah I was up a bit later than usual last night.. Sorry about that. Your numbers are right just know that the lowest frequency is a bit rounded. To be exact I get about 3.579620 which is a bit higher than 3.579600 but it shouldnt really make much difference. The 6AN8 reactance tube is confirmed good. I'll check the voltage on the plate of the pentode of the 6AN8 next.

[SwizzyMan]

There must have been some intermittent connection in the socket of the reactance tube because now the color is solidly locked!! Frequency is on the dot! But I do have the wrong colors for sure and the hue/tint control changes the colors but doesnt give me all the right colors. I do know that I can do a touch up by adjusting the coil that is controlled in a way by the hue control (the control seems to act like a variable inductor?). But i think I should do a color temperature setup first. Your thoughts?

[old_tv_nut]

By the way, too much capacitance across the crystal will lessen the effect of the reactance tube, so, since you see the frequency being pulled a good amount by the added cap, it may be better to remove it while looking for other causes.

I'm going to bed now, will check in tomorrow to read the latest. Good luck!