New project - Canadian RCA CTC 38

[Gunslinger]

Originally Posted by zenith2134

You lucky dog. That is in as-new condition!
CTC38s didn't have such a great reputation, I've read. However the picture looks quite good from what I can tell.

Actually I loved the CTC38 and 39's. I knew most of the problems.

Bad news...I no longer have the schematics for them. It appears all i saved were CTC169 and upward.

As far as parts, I may have the fliter cans.

[maxhifi]

The TV has been doing a good job of entertaining me since I got it working... I have it connected to Netflix via Wi-Fi. I've wanted a tube RCA for a while and this seemed like a good one to jump at... I've heard from VK members that tube RCAs have superior colour to Zeniths and I wanted to check it out for myself.

[maxhifi]

Originally Posted by Gunslinger

Actually I loved the CTC38 and 39's. I knew most of the problems.

Bad news...I no longer have the schematics for them. It appears all i saved were CTC169 and upward.

As far as parts, I may have the fliter cans.

I think I may want to pick your brain a bit - what problems are we talking about? Mine came with the high voltage tubes/horizontal tubes all replaced with 1970 vintage made in japan RCA red label tubes, which added up with the RCA factory service sticker from 1970 on the back of the set.

[maxhifi]

After watching the tv all year decided to give it some attention. I adjusted purity, convergence, and grey scale. Then I adjusted linearity and pin cushion. Man, does it ever make a nice picture now! I also replaced the nuvistor in the tuner,
which sharpened up the picture a lot. Only problem is the vertical position seems low (I.e. The black bar on the bottom of a 16x9 picture is narrower than the top bar when size and linearity are correct) and I have no clue how to adjust it. It's still got a bit of a wave as it did before, but I haven't changed any electrolytic capacitors yet. It's almost unbelievable how good the colour is now, it looks better than a lot of newer CRT televisions.

Also another question - an ideas what the blue knob just in front of the purity rings is for? (See pic)

[Gunslinger]

Originally Posted by maxhifi

After watching the tv all year decided to give it some attention. I adjusted purity, convergence, and grey scale. Then I adjusted linearity and pin cushion. Man, does it ever make a nice picture now! I also replaced the nuvistor in the tuner,
which sharpened up the picture a lot. Only problem is the vertical position seems low (I.e. The black bar on the bottom of a 16x9 picture is narrower than the top bar when size and linearity are correct) and I have no clue how to adjust it. It's still got a bit of a wave as it did before, but I haven't changed any electrolytic capacitors yet. It's almost unbelievable how good the colour is now, it looks better than a lot of newer CRT televisions.

Also another question - an ideas what the blue knob just in front of the purity rings is for? (See pic)

Blue knob is blue lateral adjustment. CTC 38's had transistors in the IF stage go bad. They are 4 legged; ECG 161 was listed as replacement but were not a good choice if I remember correctly. The inverter transistors failed also. You will need #124754 and 124753 for OEM parts. I probably still have them. I hve never had to replace a nuvistor tube in a RCA tuner ever.

[maxhifi]

Originally Posted by Gunslinger

Blue knob is blue lateral adjustment. CTC 38's had transistors in the IF stage go bad. They are 4 legged; ECG 161 was listed as replacement but were not a good choice if I remember correctly. The inverter transistors failed also. You will need #124754 and 124753 for OEM parts. I probably still have them. I hve never had to replace a nuvistor tube in a RCA tuner ever.

Hey thank you for the response !

I subsequently figured out that what actually removed the grain from the picture was not changing the nuvistor, as I thought, but disturbing the 300/75 ohm balun on the back of the set. It had a bad connection. What symptoms would result in needing those transistors?

My real concern now is how to adjust vertical centering. I noticed older sets have a control for this, but this one doesn't so far as I can tell.

[zeno]

Most common vert lin problem in most sets is the electrolytic
in the cathode of the vert out. In yours a 50 mfd 150V
its under the chassis near the damper socket. Its also in series with
a 25mfd in front most can.
The IF would cause no pix or snd or a very weak washed out pix.
Also common on the upright RCA portables & YES OEM best !
And yes nuvitars were reliable, think I only changed 1 or 2.

73 Zeno

[maxhifi]

Would a vertical linearity problem extend to vertical centering ? So far as linearity goes I am pretty happy, although the height control I near the end of it's range.

I definitely have a great pic and buzz free sound, and there's plenty of contrast so I don't have a lot of worries about the IF. I am trying to figure out a convenient way to replace the four multi section capacitors without resorting to re stuffing them. Maybe a piece of perf board on stand offs will do it. I don't really care how it looks but it's got to work properly and not introduce any ground loops.

I will pull the chassis and change that cathode cap tonight, I Am pretty sure I have a new one somewhere.

[Gunslinger]

I may have a new filter capacitor. It would be new old stock. I will look tomorrow. Wish I had part numbers in my mind....I think it may be 124791

[maxhifi]

Replaced the two capacitors, C7 and C2D. Both checked okay on radio shack multi meter for value. Still picture is a bit low on screen, and I noticed there's some choppiness to the test pattern at some settings of the linearity control, cleaning didn't seem to help. Here is the latest best effort convergence/ linearity. Notice the choppiness, some horizontal lines even doubling where they shouldn't.

[andy]

...

[Eric H]

You may be expecting too much perfection from this set, that picture looks darn good from here, these old sets often weren't perfect even when new.

Read some old Consumer Reports on TV's, they would often find too much overscan, poor linerity in the horizontal, bad geometery, etc...

What matters is how it looks on program material, a test pattern will show up all kinds of minor tics that aren't a problem in regular use.

[Kamakiri]

I agree, I don't know that you'll get it any better than that.

[maxhifi]

Thanks for the encouragement guys!!

The back is screwed back on to the tv and the SAMs folder filed, I get a little bit obsessive over these things before I can declare victory. This is the "main" tv in my house, and I use it quite regularly. I enjoy the reactions of gusts who have never seen such an "antique" make a great picture.

The convergence was Actually quite badly out before I touched it up though. It's amazing how far I have come with this, in 2010 before I joined videokarma I was absolutely afraid of touching convergence, I was convinced I would mess it up so badly I would ruin a tv instead of make it better.

Originally Posted by Eric H

Read some old Consumer Reports on TV's, they would often find too much overscan, poor linerity in the horizontal, bad geometery, etc...
.

I really would like to read those. I wonder who was "the best". My gut tells me the sony trinitron by a mile, but I kind of like having a tube chassis in the living room.

[zeno]

I agree the screenshots look damn good. You could
do a major recap & change a bunch of slightly off resistors
but not worth the risk. Too much can go wrong with little
reward. At this point it looks as good as they did in the
olden days....

73 Zeno