A quick CTC 16 question
 

I recently picked up a CTC 16 it's in amazing condition. The cabinet looks nearly new and so does the flyback. First inspection shows some odd stuff. The UHF knob doesn't turn at all, the pilot light for the VHF knob is blown, the cups in the picture tube look brand new, the chassis just has some light dust on it mostly close to the picture tube, all the tubes look to be original RCA, the flyback looks very good, but I see the tube has a parallel isolater on it. I can't tell if it's low hour or high hour? All the screws are still in the set, the Yoke isn't over heated and brittle. It's odd. Now the bad. I the previous owner had it for 20 years and was saving it with the intention of "Doing something Crafty" so she never used it. When she did decide to sell it she plugged it in and got a blue raster. Considering I dont know enough about my test jig to use it, I went to my storage unit and plugged it in to see what happens. After wiggling some tubes the TV fired right up like I was using it last night. Albeit with a dim blue screen. The bias switch was set to the bottom and the grid controls were set to about a 1/4 turn from off. I tried running the set without the Isolation Brightener for a second and the picture was the same with no difference in brightness. Unfortunately my B&K 465 doesn't have the adapter to test the tube. I'm thinking of buying a brightener and seeing if I can make an adapter, but I don't know the G1 and G2 settings for that tube. Is there anyway to gauge the health of this set before I start recapping the chassis?

Don't put on a brightener or otherwise "clean" or boost the tube with a tester.

Put the service switch into the service position and advance the G2 controls to get a dim line on all three colors (just extinguished is better). Move the bias switch if you need to in order to get a line across the screen. if you can achieve this, put the switch back to normal and you should have a raster.

If you can't get a service line with your three G2s up or you can but aren't getting a raster, you need to troubleshoot this and not just guess that the tube is weak. For all we know, the last guy put the booster on it for the same reason you think it needs one - it may not.

John

Honestly I don't know if it needs a booster. But I turned the service switch and got 2 lines I forget what color but I didn't see red. I want to say it was blue and white but I'm not 100%

I am getting snow on the screen and it changes with turning the dial.


I would like to make a test adapter if someone could help me out with that. This way I can tell if the guns are infact weak.

OK, you've got a raster. From what you're saying, there's a high probability it's got a weak tube. For the service line, the "screen controls" (I called them G2 in my last post) should give you a red, green, and blue line. White is most likely the green and blue superimposed. Normal procedure is to advance them until they light, then back off until they just extinguish. If you didn't see red, the red gun might be very weak.

Best thing to do if everything else seem good and there's no smell of something getting hot (btw, check the filter cans - none of them should be much more than room temp) then let her run a few hours. If the TV hasn't been run in 20 years it might pick up emission.

Regarding a tester, you can make a universal adapter using color coded clip leads that will work on any tube. I did this on my B&K 467 during the last of the RPTV years when I kept running into new projection tubes and B&K no longer supporting the 467.

What kind of CRT machine do you have?

EDIT: oops, didn't see you had a 465.. Those adapters are fairly easy to find and cheap enough, but while the 465 is a good tester, it's *brutal* on the tube for any restore functions.

John

If that's an isolation brightener and not just 'brightener', there's a chance it was installed due to a heater-cathode short. In any case, you need a decent tester to be sure what you got.

[EDIT.] If the britener has a switch, what position was it in?

Follow JohCT first with isolation on. You can follow almost any delta tube directions. We did the "just gone line" method.
Isolation is for H-K short. When it happens its usually int. When it shorts the bad guns cathode gets pulled to GND. This makes the screen BRITE of that color
with streaks & retrace lines. You can often LIGHTLY tap the CRT neck
to make it come & go.
SO try a set up & see if you can get a B&W raster. If you cant check the
CRT voltages on the K's, G1's & G-2's for next step.
BTW you can make a universal adapter. You need checker
schematic, cable connector, & those hook on test leads. It can check almost
any jug.

73 Zeno

i'm not sure, but this may be the right one for your tester.

https://2024onlineshop.ru/product/275218033090


its also on e-bay for more $$$

i'm not sure, but this may be the right one for your tester.

https://2024onlineshop.ru/product/275218033090

nope, not it, what is the number of the right one?

One thing on the CTC-16 is the jumper wires on the chroma board tend to corrode open and they can kill individual guns and mess with HV regulator behavior...A number of newer chassis also have this and it's something to be aware of.

OK..
THIS looks like the one.

If you really want to test the tube that is,

https://www.ebay.com/itm/12630797673...Bk9SR4689I7qYw

And, someone nabbed it!

I actually Just bought it!

Thank you I wasn't aware of that. So I should be able to probe that plug and see if the voltages are missing right?

I don't see any retrace lines, other than being blue it's a good picture. I'm wondering could I turn off all the colors then bring up one color at a time to see if all the guns work?

I didn't see a switch, and it looks like it just does isolation not brightening. It would be nice of it was a chassis problem that someone tried to fix with the isolation transformer. Wouldn't the cups the dark if it was shorted? Like wouldn't it need to be a high hour tube?

Also surprisingly the filters didn't really get hot

Not only can the jumpers on the color PCB be a source of pain on the 16, but also the ground points can come lose and cause issues, got to make sure there is no fractured solder at any on the ground points.

An issue I had with my CTC-16XL was the the orange drop capacitors near the Y-amps, these tend to get very hot and toasted and prone to failure.

shameless promo! :D

https://www.youtube.com/watch?v=7V3etX2NsS4

deleted

I worked on a TON of these back in the day.
First things first. Do a visual and check for the obvious; poke around and look for overheated components, wires, etc. Go under the chassis in the power supply section. If the set has any time on it you will find corroded solder joints, bad/ ready to fail solder terminals, resistors, etc. Those power resistors generated a LOT of heat. It’s best to remove the power resistors from the terminal strip, sand the leads clean and clean the terminal strip lugs. If you’re lucky you’ll succeed. If not, replace. Replace or re-stuff the canned electrolytics. If they are the originals they can (no pun intended) go at any time. As previously mentioned, re-solder every circuit board’s ground lugs. Without a good power supply you have nothing.


Also, have you checked the tubes?

Once sure the basics are present, you can tackle the rest.

Certainly, that's the way we accessed the condition of those tubes back then. Turn all screens down and advance each one. They should roughly be the same but be aware that due to the color spectrum, the green will be the brightest, the red close but not as bright, and the blue (even with a strong gun) won't look as bright and crisp and the green and red.

If your blue looks good, the red and green should look better. From your description, you have a soft tube. It might perk up if you run it a few hours continuously.



We don't know who worked on it and we don't know why he tried it or if he even knew what he tried was simply an isolation "brightener" (he may not have know the difference between a brightener, and isolator, or a combo device).

I worked on tons of those when they were daily drivers and while soft guns were common (I must have changed several hundred 21" roundies), heater to cathode shorts were not all that common in these tubes.

My guess is that they correctly diagnosed a weak picture tube and added the isolator thinking it was a heater boost brightener.

John

WOW, this BBS sure has been glitching out a lot lately! :yes::sigh:

I’m getting this message a lot!
“The server is too busy at the moment. Please try again later.”

jr

Me too

like this, it's borderline unusable :(

Back in the day we tried an isolator a couple of times. It smeared out fine detail in the pic due to parasitic capacitance-to-ground (since video goes in via the cathodes). Don't recall ever trying it on a rectangular tube, though it might do better due to the unit's smaller size.

What does an isolator do really?
Cause it seems that the CRT already has it's own winding off the main power transformer separate from everything, save for a pull up to 200-300v, is it not already isolated by that heater being powered that way?
Or is this isolator removing that path to the pull up and any ref to ground through it?

OK I didn't read your post well enough. Separate winding on power xfmr. Dumb senior moment! DOH. :screwy: Parasitic capacitance would still be a problem though.

The CRT filament usually shared its power transformer winding with the 6BK4 high voltage regulator tube. There was usually a .1 cap to ground from the semi- floating filament circuit. When needing an isolation transformer because of a heater to cathode short in one of the guns, removing that .1 did help with the smearing issue sometimes.