RCA CTC4: the barberized Seville

[stromberg6]

Originally Posted by Electronic M

Wow such nice colorimetry. Is yours using a 21AXP22 ?

Thanks for the encouragement all.

A humorous development is that the main power fuse that had a new one jumpered over it was actually replaced by one less than half the current rating of the original, and that device used to jumper it had a cracked rivet causing an open circuit. The replacement fuse was good so I have to doubt that this set saw any use since the time that the original fuse popped.

Yes, a 21AX. It seems to be a very early production tube, as the screen is greenish like a 19VP22 instead of kind of gray like later tubes. Also no "A" suffix in type number. It produces amazing color when set up correctly. Probably would look spectacular in a 21CT55.
Good luck with yours! We all will help any way we can!!
Kevin

[miniman82]

It does look good in a 21CT55, here's my green screen 21AX:




Bob G also has an original production green tinted AX in his CT55, they make a slightly more saturated picture than the later whitish ones. It looks just like a 21" CT-100, which makes sense.

[Electronic M]

Thanks for the explanation Bob!

I remember that Jr_tech wanted to know how the getthers looked. They look silver and dark gray to me....



I decided to pull the CRT yesterday here are some pictures.







I've also slowly been cleaning 57 years worth of grime off the chassis.


I've been recaping too. Here is the completed IF board.

The two ceramic cased ones I managed to restuff, but the rest had "bakelitized" paper tubes the ends of which my soldering iron could not melt or even soften! I had to double up to get two of the values....I replaced a .027 with a .022 and a .0047 in parallel, and I replaced a .056 with a .047 and a .01 in parallel ( I know this not wonderfully exact, but it is an improvement over the .068 maroon drop that was in there).

I also remounted the IF shield after the recap.


With luck in the next couple of days I'll have the recapping done good enough to do a test power up.

I have dug out of my stocks all the tubes this set needs except for the Damper, H output, HV rect., the 6CL6s, the 6AN8s, and the 6AZ8s (I managed to find a majority of RCA branded used and NOS tubes for this set). I'm going to sift through my unboxed tubes and see if I have any. If not I'll see if nostalgiaair lists any sub types that I might have.

[miniman82]

Damn, this thing's gonna come back to life faster than my Director 21 did! Show us color bars!!!

[ohohyodafarted]

Originally Posted by jr_tech

Actually it is even less than that... a torr is 1 mm of Hg pressure, and atmospheric pressure is 760 mm of Hg, so 10 -6 torr is 1/760,000,000 of an atmosphere.

jr

You are corrrect. I always get that confused because most of the scale on our militor meter is graduated from 1 torr to .001 torr and the top end of the scale from 1 torr to 1Atmosphere is only 1 graduation, so I always think 1 torr is 1 atmosphere. Sorry for my brain fart :-)

[Electronic M]

Well since my last post I found replacements for the missing damper, HV rect, and H output tubes, but I have not found the others in my stocks yet....Also it seems that there are no compatible types according to two tube sites I've checked.

I finished replacing all the paper caps, and found that this set more closely matches the riders schematic than the Sam's folder from the ETF.
The only cardboard tubes left under chassis are either lytics or restuffed papers.


I realized that one of the doubled up caps on the IF board I had a single-cap replacement for and decided to swap my first replacement for it as I needed the .0047 that was part of the first replacement elsewhere.


After doing all that it was very late and I decided to call it a night thinking I had reached my goal of ousting all the paper caps, then as my head hit the pillow I thought "Oh sh!t I forgot three! Oh well tomorrow then.", and this morning I swapped them out. Now I can say all the papers are gone.


Now to try to find the remaining tubes and hopefully get enough new lytics in for a test power up.

Yesterday was basically me barely managing to scratch up enough caps to replace the papers, and now it will be the remaining tubes and the lytics. Wish me luck!

[timmy]

so what you are saying is that for a crt like the 21fb,21ax needs10-6 torr of vacuum so what would the hg be for that amount? i ask because i have a gauge that i think has hg on it and is used for vacuum. i only thought vacuum was measured in inches, like in autos.

[jr_tech]

One atmosphere of pressure pushes on us with about 14.7 pounds/square inch. That pressure will support a column of Hg about 29.9 inches high in a Hg barometer... that is about 760 mm of Hg. One mm of Hg is defined as 0ne Torr.

So to go from inches(of Hg) to Torr, just multiply by 25.4 (mm/inch conversion).

jr

[timmy]

so this is physics, wow, so then 10-6 would be what torr because there is 2 numbers. one mm hg defines one torr but what number to use, 10-6, why a dash and not a point.

[miniman82]

It's 10 to the minus 6, scientific notation...

[timmy]

ok thanks... i was never good with math,lol....

[ohohyodafarted]

or in simple terms 10 to -6 torr is .000001 of 1/760th of an atmosphere

(one atmosphere being 14.7PSI) so 14.7PSI * .000001 / 760 = 1.934 * 10 to -8

in PSI it would be 0.00000001934 PSI or as a fraction

1.934
------------- PSI
100,000,000

Someone please check my math to make sure I have all the decimal points correct. I came up with 1.9342105e-8 PSI

[WA3WLJ]

Neon Bulb Time is from 1 Torr to 1 millitorr.
We can't have any spacecraft power on or else the chance of "corona" arc is high !

[ChrisW6ATV]

I see the CRT was rebuilt near the end of 1965.

[Penthode]

Congratulations on the CTC4!

I have a question for CTC4 owners. I noticed that RCA in I believe this chassis only, tried to get away with taking the intercarrier audio directly from the video detector instead of having a separate intercarrier detector. The separate detector for intercarrier sound would facilitate better sound rejection to minimize the 920kHz beat.

I believe this was unique only to the CTC4. Do any of you with working CTC4's see the difference with later sets or actually see any detrimental effect of the possibly greater 920kHz interference?