RCA CTC...Something? poor HV output.

[Findm-Keepm]

Originally Posted by Arcanine

It may have been suffering low HV before, but no longer. The new focus rectifier, and the shuffling of tubes... And I also cleaned up some dust build up inside the HV cup on top of the flyback box since there was some arcing in there, and I also changed out the anode lead to the CRT with a 50kV rated wire from an old computer monitor, which took care of all the arcing, and makes a nice connection to the CRT, as well.

(and a minor adjustment to my meter so the needle would stop sticking)



25kV! Now, the Hi-Volt adjust is cranked open all the way, so that could be something else, time will tell once it gets more issues, and caps changed.

Now for everything else. One step at a time. This was a big step for me, very excited to see color, 25kV on the meter, and a bright stable image. This will be a nice set again soon!

Be careful with the HV and a bad/low output focus rectifier. Folks see low HV, crank up the HV, and then have out of focus pix, so they replace the focus rectifier tube or diode, and now they have too much HV, and too much focus current - it smokes the focus coil on these old sets (happened to my CTC16) - it's a no wonder the focus coils were QT parts.

[timmy]

Could be the 1.5 meg resistors around the hv pot, may have drifted.

[Electronic M]

I'm overhauling it for Arcanine. So rather than fill my PM box and keep it hidden, here is a public status update.

I started work on it today. As gotten screen shots:

As can be seen the grayscale was very yellow. I also had to tweak the chroma osc. to get the color bars shot.

I could not get setup lines with the service switch and had to resort to playing with the brightness and CRT bias switch to get them.....The blue was still VERY weak with it's control maxed (had to douse the lights to balance the lines with the G2 knobs)....I'm probably going to test the gun biases later to see if something is messing with the blue.

That got me here:

I decided to verify HV level on my probe. With the set running on 117VAC it's producing 23.5KV, which is within the 22-24KV listed in the sam's.

I removed the chassis and decided to look at the ruined power switch. The shaft of the vol pot/power switch on the donor CTC-20 chassis was 1/2" too short, and the switch was different so that was eliminated as an option.
Opening the original switch revealed that a piece of black phenolic (SP?) that connects the switch contacts to the shaft broke. Attempt to duplicate it failed due to limited tools and lack of knowledge of the shape of the damaged part.
I then remembered I had some spare pots with similar switch shells. None of my spare pots had the right shaft length so I tried to transplant the switch section alone. One had different guts that I ruined trying to adapt to the original. The second was identical to the original switch section and I was able to mount it successfully. It works well, and no one would ever think it was a replacement. The white piece on the original shaft in the picture is what the broken black piece in the original switch should have looked like.


Now that the grayscale is right and the power switch works again, it is on to other work.....Like changing original caps of types I do not trust, going over the vertical circuit, and some adjustments, etc.

[Findm-Keepm]

Looking good! What's the HOT cathode current running?

Always replace the cap attached to the cathode of the 'GF7 - that cap, more than any will cause problems with the vertical. Also go over the ground eyelets on the boards. Vertical / horizontal sync problems are generally caused by resistors way out of tolerance. I've restored three CTC16 sets, and outside of electros, the cathode cap, the sync resistors, and a thermistor or two, I've never replaced a single film cap.

Also clean the pins on the IF tubes - video will suffer If problems there.

Like I said, looking real good!!

[Arcanine]

Oh wow. Those colors are really good. You really managed to get rid of that yellow it was suffering.

Excited to see the progress. This was just one of those things, I was so let down when I got it home and it almost was completely dead, I was so disappointed I didn't find my self wanting to work on it.

I got it as far as proper HV, and color on the screen then passed it on to you.

When we tested my CRT, didn't it show all the guns were pretty good? Seems strange blue doesn't want to play nice.

[Electronic M]

Originally Posted by Arcanine

Oh wow. Those colors are really good. You really managed to get rid of that yellow it was suffering.

Excited to see the progress. This was just one of those things, I was so let down when I got it home and it almost was completely dead, I was so disappointed I didn't find my self wanting to work on it.

I got it as far as proper HV, and color on the screen then passed it on to you.

When we tested my CRT, didn't it show all the guns were pretty good? Seems strange blue doesn't want to play nice.

IIRC it was blue that failed the color tracking test. This could be a side effect of that, or something else could be off in the gun bias circuits.

[Arcanine]

Originally Posted by Electronic M

IIRC it was blue that failed the color tracking test. This could be a side effect of that, or something else could be off in the gun bias circuits.

It may wake up. I have no idea how many years that TV was sleeping and how long that CRT went unused. It seems like it has a hell of a picture.

[Electronic M]

Quick progress. The only vertical stage resistor under 2M I did not check (excluding controls which I skipped last session) was near the controls, and it was wide open....R102 150K .....I replaced it with another one on the top end of it's tolerance (t'was all I could find ATM).

Replacing it got me this.


I can't get linearity quite right though.....If I do the bottom (and sometimes top) is under-scanned, and centering is maxed downwards.....It's progress though.

This is the HO tube that died. I can't find any ID marks on it.

[Arcanine]

Originally Posted by Electronic M

Quick progress. The only vertical stage resistor under 2M I did not check (excluding controls which I skipped last session) was near the controls, and it was wide open....R102 150K .....I replaced it with another one on the top end of it's tolerance (t'was all I could find ATM).

Replacing it got me this.


I can't get linearity quite right though.....If I do the bottom (and sometimes top) is under-scanned, and centering is maxed downwards.....It's progress though.

This is the HO tube that died. I can't find any ID marks on it.

Oh... crap... That's one of my Dentron part numbered tubes. It's an unusual 6LQ6 tube. I tried it in the TV early on, and found it only works in HF amplifiers and not televisions despite being the same number. It's an optimized tube for HF amplification and not television.

Dentron's part number for those is D-50. http://www.radiowrench.com/sonic/so02182.html is what it came out of.

Those... are very expensive and hard to find (At least they were 9 years ago. Not looked in a long time). I forgot it was in that lot of tubes. I need to know if that RCA 6LQ6 tests healthy, if it does I can rearrange the HF amp's tubes and use the RCA as the driver.

If you don't mind test that RCA H-Out tube for me.

Don't worry dude accidents happen. I'm not mad at you. I'm MUCH happier to see a full picture on the screen of that TV then I am upset over a broken Dentron tube.

[Electronic M]

About done.

I went after the vertical linearity issue this past week. I made sure all resistors in the circuit were good and changed any marginally bad testing caps. One odd thing I found is that a cap in the output cathode circuit was listed as a .47, but the original installed part was a .15uF....I stuck with the value was installed after trying a .47 with no improvement.
I'm not proud of my replacement for that .0082 1KV orange drop....The best I could do, since I don't stock new caps over 630V, was to connect a few 2KV rated blue disc caps salvaged from 90's BPC sets in parallel for the correct value as measured on my cap testers.....Not pretty, but it should function well...It's the kind of thing I regularly put in my sets when there is nothing better on hand, but I prefer not to do that in sets repaired for others (looks unprofessional, and I'm not right there laying in wait to replace if it fails).


The vertical linearity issues were watchable, but bad enough to bother me.....After all that passive part verification (with little improvement) I was about ready to give up and say the linearity was not going to get better, but then I remembered that when it still had the under-scan issue tube swapping showed linearity differences....So I swapped the vertical tube and things got better...Much better.


One odd thing that happened is that after around 1 hour on the flyback got rather hot....I know because I started smelling wax, then heard a sizzling noise from the HV cage. As soon as that happened I switched it off and opened the HV cage immediately the sizzling continued and was visually confirmed to be coming from the center of the fly windings, and a drop or two of wax had freshly landed on the small existent wax stalagmites. Many of my sets have evidence of this happening before and during my ownership, but I've never seen or heard it in action before....So I don't know whether to interpret this as normal or a warning sign. I had checked cathode current to be just under 200mA not more than 5 minutes before this happened.....
5-10 minutes after powering it off I powered it back on to do a few adjustments for 10-20 minutes....It worked fine, and it did not sizzle again.
Might be a good idea for you to drill some vent holes in the HV cage and add a computer fan to help cool it.

At this point all there is worth doing is to test all the tubes, test the lytics/replace any bad ones (if present) and reassemble it. The cans were cool after over an hour run time, and it's working like a champ, so I'm not sure the tubes and lytics need my attention.....If you want me to I'll go over them, otherwise I could skip them for speed.

Chroma synch has been reliable, but I make no guarantees that it will hold after a bumpy car ride back to your place, so I'll give you some instructions on how to adjust it when you pick it up.

If you are worried about the fly I could work on the CTC-20 after returning the 16....Then if the 16 dies (and if I can fix the 20) I could swap you a working CTC-20....

Let me know what you think.

[Arcanine]

Originally Posted by Electronic M

About done.

I went after the vertical linearity issue this past week. I made sure all resistors in the circuit were good and changed any marginally bad testing caps. One odd thing I found is that a cap in the output cathode circuit was listed as a .47, but the original installed part was a .15uF....I stuck with the value was installed after trying a .47 with no improvement.
I'm not proud of my replacement for that .0082 1KV orange drop....The best I could do, since I don't stock new caps over 630V, was to connect a few 2KV rated blue disc caps salvaged from 90's BPC sets in parallel for the correct value as measured on my cap testers.....Not pretty, but it should function well...It's the kind of thing I regularly put in my sets when there is nothing better on hand, but I prefer not to do that in sets repaired for others (looks unprofessional, and I'm not right there laying in wait to replace if it fails).


The vertical linearity issues were watchable, but bad enough to bother me.....After all that passive part verification (with little improvement) I was about ready to give up and say the linearity was not going to get better, but then I remembered that when it still had the under-scan issue tube swapping showed linearity differences....So I swapped the vertical tube and things got better...Much better.


One odd thing that happened is that after around 1 hour on the flyback got rather hot....I know because I started smelling wax, then heard a sizzling noise from the HV cage. As soon as that happened I switched it off and opened the HV cage immediately the sizzling continued and was visually confirmed to be coming from the center of the fly windings, and a drop or two of wax had freshly landed on the small existent wax stalagmites. Many of my sets have evidence of this happening before and during my ownership, but I've never seen or heard it in action before....So I don't know whether to interpret this as normal or a warning sign. I had checked cathode current to be just under 200mA not more than 5 minutes before this happened.....
5-10 minutes after powering it off I powered it back on to do a few adjustments for 10-20 minutes....It worked fine, and it did not sizzle again.
Might be a good idea for you to drill some vent holes in the HV cage and add a computer fan to help cool it.

At this point all there is worth doing is to test all the tubes, test the lytics/replace any bad ones (if present) and reassemble it. The cans were cool after over an hour run time, and it's working like a champ, so I'm not sure the tubes and lytics need my attention.....If you want me to I'll go over them, otherwise I could skip them for speed.

Chroma synch has been reliable, but I make no guarantees that it will hold after a bumpy car ride back to your place, so I'll give you some instructions on how to adjust it when you pick it up.

If you are worried about the fly I could work on the CTC-20 after returning the 16....Then if the 16 dies (and if I can fix the 20) I could swap you a working CTC-20....

Let me know what you think.

I honestly never thought I would see that TV produce even a half watchable picture. That is as close to perfect as I'd call a set that old.

I would not worry about your repair. I can source a new cap and replace it if your repair ever fails.

As for the Flyback, I had the same thing happen where it got very hot for no reason what so ever. Judging by the wax build up in there, it's been doing that for a very long time for no real reason. Unless it's acting up internally, like windings have fused or something.

Maybe someone here has a spare CTC16 Fly I can get as a spare.

As for the rest of it, it looks like it has a great picture. Pretty excited to see it's alive and working again.

[Findm-Keepm]

Originally Posted by Arcanine

I honestly never thought I would see that TV produce even a half watchable picture. That is as close to perfect as I'd call a set that old.

Looks great! ElectronicM done you right! Great job!

[Electronic M]

Glad your happy with it. Roundys tend to be a pain in the but to fix for first timers, but often teach them a lot about what can and will go wrong in these sets.

Do you want me to check the tubes and or lytic cans, or should I just bolt it back together and call it done?

[Arcanine]

Originally Posted by Electronic M

Glad your happy with it. Roundys tend to be a pain in the but to fix for first timers, but often teach them a lot about what can and will go wrong in these sets.

Do you want me to check the tubes and or lytic cans, or should I just bolt it back together and call it done?

Yeah go ahead and test them. May as well make sure they're okay before calling it gone be cause I plan to put it in to service and actually watch the thing.

Make sure you find a good 6LQ6, for me, too.

[Electronic M]

Originally Posted by Arcanine

Yeah go ahead and test them. May as well make sure they're okay before calling it gone be cause I plan to put it in to service and actually watch the thing.

Make sure you find a good 6LQ6, for me, too.

Will do.

I have only one good spare 6JS6/6LQ6 in my stocks. I kinda hate to let go of it since that CTC-20 needs one (HO socket is empty), and I have at least 6 working sets that use that tube...

I wish I could trade some other sweep tubes that I have in duplicate++ for some 6LQ6 tubes.