RCA CTC4: the barberized Seville

[Glenz75]

Far out - What a set Seeing that chassis makes working on black and white sets seem rather basic Good luck with your restoration of this beast! Cheers.

[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!!!

[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...

[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 !

[timmy]

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

[ChrisW6ATV]

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

[Electronic M]

Okay! I'll start with the questions....

Is it necessary to replace the seleniums before a power up?

And to those whom have installed 1N4007s in place of the seleniums what if any added series resistance value did you use?

And to those who have used newer CRT types than the 21AXP (Nick...) how did you connect the HV button on the CRT to the HV connector on the HV cage? I've got my fingers crossed that this can be safely done without cutting the HV plug off the plastic CRT cover as I entertain the hope of someday having a good 21AXP22 to install......

Also which tubes are supposed to have shields on them?

As for progress......

I've disconnected the Doubler and B+ from the transformer and done a power up to confirm that the power xfmr is still good. The fillaments lit so it would seem that my power transformer is still good.

I'm presently variacing the set with only the doubler caps and seleniums connected to the B+ winding on the xfmr (I unsoldered the B+ lines) so I can reform 3 of the lytics and check the seleniums under power simultaneously.

I've been continuing to clean the chassis as well.
I thoroughly cleaned the inside HV cage including removing the HV rectifier cup for a cleaning.
The place where the HV rectifier cap connects to the fly was missing most of it's wax and kinda loose so I took some dripped wax and built up the wax around it for added support. I was concerned that the the connection on that lead was open so I checked the resistance between it and the HOT cap lead and got within 10% of what sam's lists that resistance value to be which is a good sign. I also for the briefest of moments touched the barrel of my soldering iron to the wax on the HV winding of the fly to melt the outer layer of wax in order to fill in some small cracks in the wax coating.
I replaced the HV cage lytics as well. I replaced the 20uF 25V caps with 22uF 250V replacements, and the 5uF 25V with two 2.2uF 63V Radio Shack "how the heck can new caps have some ESR???" specials connected in parallel (I'll likely change these turkeys later for a better part).

Here are some pictures.....More can be found in the link from the first post in this thread....












EDIT: yes the title is a me using a word play on the title of the opera "The Barber of Seville" as a pun....Glad one a' ya uncultured swine (I'm joking here) gets it. And NO I'm not a fan of Opera (classical aint bad, and I like most popular music from the 50's to the 80's, but Big Band/Swing is what I really LOVE).

[miniman82]

Originally Posted by Electronic M

Is it necessary to replace the seleniums before a power up? And to those whom have installed 1N4007s in place of the seleniums what if any added series resistance value did you use?

My CTC-4 came with modern silicon rectifiers already in it, I just run it a little low on input voltage and read B+ till it's correct. I toyed with resistors before, but they dissipate a ton of heat.

And to those who have used newer CRT types than the 21AXP (Nick...) how did you connect the HV button on the CRT to the HV connector on the HV cage?

The HV tower uses the exact same connection as a Tektronix o-scope, that's where I stole my lead from. I had to desolder the original wire, then soldered on a HV cup with a longer wire that matches the connection on the CRT (the type with a silicone cup). I think I might have given the one I made to Bob or Mark, you can make your own the same way if you get your hands on one of those leads.

Here's an Ebay link, but $70 seems pretty steep for just the wire: http://www.ebay.com/itm/Tektronix-pn...item43ac0df518

Perhaps you can cannibalize a broken scope?

Also which tubes are supposed to have shields on them?

Just the ones that have grounding fingers attached to the chassis.