RCA CTC39XBJ alignment and tweak.

[freakaftr8]

Well I figured I would start a new thread on this one since the other thread title was confusing. heres what I got so far with no Sam's schematic.

I've performed a complete alignment. Purity and convergence is about as best as I can get. honestly I have to give myself a pat on the back on this one. The old CTC39 I had when I was a kid in the late 80s I could never get the convergence perfect. well This one I managed to. Maybe it's the 25V CRT? My old CTC39 had the 23v CRT, which was the early version, was a PITA.

Anyway I started noticing the H width seemed stretched on this guy. So to confirm I hooked it up next to my Sony KV3000r. Sure enough its stretched out.

Does anyone know which coil is for horizontal width?

In the picture you can see the difference between the "LIVE" icon in the top left between the two.

[freakaftr8]

Is the horizontal efficiency coil for the width? This controls cathode current as well IIRC?

[Electronic M]

Efficiency is not width (and should be adjusted for min cathode current if you value your flyback).

I'm not familiar with RCAs after the CTC-20 (except the 25 and some early XL-100s) but many color sets of that time did not have a width control or only had a 2 position jumper wire for normal/increase width.

Back when these sets were new no consumer would complain about overscan (there was no letterboxing or graphics to highlight the effect), these sets had no B+ regulation so if you didn't have enough overscan and line voltage sagged you would get underscan (that would result in a service call), and the output tubes from new to weak enough to merit replacement would change emission enough to cause a substantial reduction in width.

My Zenith 12B13C52 that only has the jumper I've learned to not worry about anything but underscan, non-circular circles (vertical, not overscanned enough to match horizontal), and centering/linearity issues.

By alignment do you mean you adjusted the IF and tuner with a sweep generator? If not your terminology is against decades of convention...Traditionally alignment is only for RF/IF circuits, NOT adjustment of sweep/convergence systems...That is called Setup Proceedure.

[freakaftr8]

I meant convergence and purity alignment. Sorry. Unfortunately if I had access to a vectorscope, I would be all over it, however as far as the naked eye can see, I've been watching for subtle differences between this and my Sony KV3000R. Believe it or not, the RCA seems to handle this very well. Especially when there is fast action moving scenes where I have seen my CTC16 pick color sync slow. One would only assume the IF circuits seem to be well inline after a boatload of new 6GH8's and one weak 6CB6.

I'm impressed how much contrast this set produces! It can produce a really good image. As bright as the Sony surprisingly especially after I have read that the CTC39 gives a soft picture.

On another note, there's a switch on the back that says NORM and HIGH... I'm assuming this is for line voltage? I noticed a subtle difference between the width. Voltage at my house is 119.5v AC. I'm assuming that would put my switch at normal?

As far as I can tell, there is no adjustment for efficiency. At least the fly looks low hours.

[freakaftr8]

By the way this is the very same chassis that got me intrested in this vintage television and radio field.

It all started when I was about 13 years old and I was riding my bike home from school here in California. Our neighbor 2 doors down had his garage door up and inside is garage was a console TV sitting next to the wall with its back exposed. I've noticed this sitting there on and off for the next 2 weeks. Finally I went over to his house when I saw him with his garage door open ask what's up with the TV, he immediately responded with do you want it you can have it his long as you can wheel it over to your house.

Well at 13, I was ecstatic! The only tv we had was a 1973 or so RCA XL-100 in the living room that was always on and used by my stepmom and my brothers. I could never watch my Simpsons.

I plugged it in as soon as I wheeled it across the street with my father and got in my bedroom. Nothing happened, my father explained to me at the time (1989), That this was a tube type television and needed time to warm up. We waited for 10 minutes , nothing happened except for a channel indicator light.

My father said OK son were going to pull out all the vacuum tubes and take them down to Thrifty's and test them with their tube tester. He pulled the tubes because of the high voltage that might be store, and him and I packed them up with paper towels in a Box and brought them over there and tested all of them in which if I remember the Horizontal output and a few others tested bad. And I think the damper and HV rectifier here weak too. All and all I remember us purchasing 8 or so tubes from the machine. (I'm sure alot of them were the 6GH8'S ) lol.

Was one of the bonding experiences I had with my father when we brought the tubes home plug them back into the set turned it on and it came up with a bright and beautiful snowy picture.

From that point forward I learned about convergence and purity adjustments. I had it in my bedroom set up with rabbit ears so I could watch the simpsons and married with children. My life was complete and from that point forward I have always looked for exact same set that my father and I repaired. It was an RCA CTC39XAB I believe. same tv but had the 23v CRT.

I'm now 43, my father passed in 2015 and this is kind of like a relived moment, especially since I had my 6 year old help me test the tubes in this one with my Jackson tube tester to find the bad 6GH8'S.

It's been a really fun experience so far. Now he is telling me he wants this tv in his room... feels like a generational thing. He seems mesmerized by the glow of the vacuum tubes just like I was when I was a kid.

[Electronic M]

Voltage switch can probably be set to normal. You can also set it based on other metrics such as the B+ rail most directly derrived from the power transformer measuring closest to spec(or heater voltage), minimum horiz out cathode current, or if cathode current is well below max safe threshold you could set it to reduce overscan...all depends on what potential issue is the most important to you/proper opperation.

[freakaftr8]

That's what I figured. I have heard that low cathode current can cause the flyback to operate harder too. Is this right?

[Electronic M]

Originally Posted by freakaftr8

That's what I figured. I have heard that low cathode current can cause the flyback to operate harder too. Is this right?

I've never heard that before. Lower current usually equates to cooler happier flyback, or insufficient power to generate sweep and HV if you go too far down.

[freakaftr8]

Ok. I looked back on others previous posts. You are right I think I read some information wrong. I think I got that mixed up with low plate voltage .

The fly cage gets quite warm after being on for about an hour. 122 degrees roughly with my thermal laser thermometer. Of course there is quite a bit of heat that is generated with the HV tube as well. I'm thinking about installing a fan on the cage and drill some holes. I did this on a Magnavox U66 color chassis a few years back. I adjusted it for the lowest current I could achieve on that.

Still like to know what the cathode current should be on the CTC39 and where the efficiency coil is located. honestly I cannot find it anywhere.

I found a few caps with high esr in the vertical circuit that was contributing to the linearity issue, and too much vertical height with the pot turned down all the way. Also noticed green smear on images with red. Replaced a 47kohm resistor in the chroma section that reag 58kohm. Perfect now.

Impressive picture quality I have to say. actually color representation with red are better than the Trinitron behind it, which puts out an orangey red.

It is after I completely Gray scaled the picture it brought up the drives and screens to where I believe they should be, keeping the screens very low. Also had to bring down the brightness limiter. I'm not sure if that was factory or if somebody cranked it up but it sure was extremely bright and the way I like to see a good set up is when you turn the brightness all the way down you can barely make out anything on the screen.

Speaking of picture quality, is this a black matrix CRT?

[freakaftr8]

Couple screenshots so far. Way better color representation now.

Which begs me to ask this question. What does this last tube hybrid set look like stacked up to the same year xl-100 25 inch?
Better chroma/luma and black levels on high contrast images? I noticed this on the vacuum tube sets. When there is a predominantly white raster with black lettering, the image kind of blows out a little. Kind of like AGC is too high but it's not. If that makes sence.

I'm sure the xl-100 would have a more stable HV regulation. When something at my house starts up like the refrigerator or AC, the picture shrinks 8n for a split second. I'm sure the added tripler made this more stable. Ove always noticed vaccum sets have this touchy regulation.

[Electronic M]

Tube sets have no B+ regulation, and sweep and HV reg have a certain amount of reference to B+, add to that B+ is usually stepped up from line voltage 2-4x and any line fluctuation longer than the lytics time constant will be 2-4x on the B+ line.

Thank your lucky stars you don't live within 2 miles of an industrial park like I do. Used to be (and sometimes still is) that at least once every 10 sec my line voltage would sag and sweep would bloom (I could run 2-3 tube TVs at once and watch them do it in sync!). It annoyed the heck out of me then I got hold of a Sola VRT line isolation transformer...they regulate their output voltage and hold it constant with anything from 70-140 as input...they can even compensate for a missing cycle or 2 of AC.

[maxhifi]

Nice TV - you're making me want to fire up my CTC38, you're right, the picture on these old sets really looks nice.

[freakaftr8]

Funny story. We moved into this house in 1996. It was vacant for 6 or so years before that. Built in 1982. When we moved in, we noticed a voltage sag, especially in the summer.. it didn't seem to have anything to do with what we were actually running. The lights in the house would flicker constantly.

So I did a little research. In July 1997, I turned off all 220v breakers disabling AC, refrigerator, etc.. Then I went around and unplugged all other appliances so I was reduced to some bedroom lights only. This was a really hot summer evening, like 95 or so degrees like normal in the Sacramento region.

Long story short, still had the voltage drop. As it turns out, out neighbor to the right, (which moved shortly after this) was stealing power from us. He had a nearly laid out heavy gauge line dug under our side yard and under the fence tied to his house. It was pretty discreet tied to the grid before the meter. The power company was stunned when we all found out.

[Popester]

Those comparison pictures next to the Sony really look very good. Still want you to replace the burned out pilot bulb for the channel indication.

[freakaftr8]

Lol ok. That's next. Having a finicky vertical lock. Wants to roll when first powered on. When warm, picture starts flipping. Vertical locking a bit short. Havent tested V output/osc tube yet. It may be weak I'm assuming. I have repaired linearity and height issue thou..

Other pesky things were a slight purity issue on the lower left. Turns out after trying to adjust it out with the purity rings, and measuring current draw from the degausing coil, turns out the yoke needed to go a tad further in. Problem solved, but had to bring in convergence again. And I'm really finicky about convergence. that was another 1.5 hours.

I notice the top of the screen is slightly brighter than the lower. Dont know what that's about.

Another thing that's ridiculous, RCA placed the can electrolytics extremely close to the transformer. heats them up good. That will eventually become a failure point.