Restoring an RCA CTC-10 "Wynnwood".

[dtvmcdonald]

I agree that we are about to see the end of the radio shack!

Oh what memories!!! The greatest one occurred when they (Tandy)
were building their new headquarters building across from the courthouse
in Ft. Worth. I was watching, when suddenly a gas cylinder flew out of
the construction site, across two streets, and impaled itself
in the facade of the county jail. At one time mom was a receptionist
in the owner's inner sanctum area.

But I do use them all the time ... they are two blocks from my abode.
Today I bought a packet of assorted LEDs as I'm tired of replacing
pilot lamps in old radios. I've bought lots of connectors, cables,
odd batteries, etc. from them.

[Eric H]

Replaced some caps in my CTC10 over the last few days, no filters but I replaced all the caps in the Vert Osc/Output section and now I have a stable vertical and fair linearity.

The problem I'm having is the picture is not very bright and the Green and Blue Drive controls seem to have no noticeable effect at all, shouldn't they change the gray scale significantly?

The Kine Bias and all three screens are turned up full blast, the CRT is a rejuvenated jug but is currently checking 90% on all three guns with good tracking, this same jug was in a Silvertone with a CTC11 chassis before this and it wasn't very bright there either so I'm wondering if it's actually bad despite how it tests?

it's also a 21FJP22 where it should be a 21CYP22 but I don't think that should make much difference.
I have a new CRT but I don't really want to install it until I'm done with the chassis just in case I knock the neck off of something.

Here's a picture but as usual with a digital camera it looks much brighter and bluer than it is in person.
I had a color pattern on it and the color works pretty well, seem like maybe the luminance is too low though.

[DaveWM]

check the voltages at the CRT, all the pins and the HV as well. Generally brightness will be controlled by bias of the CRT and anode voltage.

a lot of times low brightness is caused by a weak video out tube. This happens on sets with directly coupled cathode (common on RCA color sets of that vintage). As the 12BH7 (or what ever the video out tube is) gets weak it conducts less and the plate voltage goes up. This in turn results in a higher voltage on the cathode of the CRT, which effectively cuts off the current flow in the CRT resulting in less brightness.

The grid and screen voltages all come into play as well so a voltage check at the CRT is the best place to start. HV will of course effect brightness as well, so that should be setup early on.

[rcaman]

looks like a worn out crt. why would you do all that work and worry using a worn out and rejuvenated crt. i dont understand that.

[miniman82]

Seems like the crt is to blame, but you won't know for sure till you check voltages at the socket. If the screen and background controls do what they are supposed to, I'd say you found the culprit.

[Eric H]

That's the thing, the screens do what they should but the green and blue drive controls seem to do nothing, or perhaps it's just too dim to see.

The rejuved tube checks like new on my B&K 466 but it could be wrong, I'll check it again with the Beltron or the Sencore tonight and see what they say.

It might just be easiest to put the new CRT in and see what happens, I need to make sure the shadow mask is ok anyhow since it was shipped to me years ago, I don't see any debris inside so I'm pretty sure it's ok.

[DaveWM]

if the voltages are off and the video out tube is good I would look around the service switch and the various power resistors there. Also the coils involved.

try adj the brightness while measuring the red cathode of the CRT, should be 360 and 280 from fully CCW to fully CW

[Eric H]

Retested the CRT with the Beltron, with these results (below) I can't see the tube being the problem.

I found the voltages I measured a while back, Left is what it is, Right is what it should be, controls can affect the results of course.

1--
2-246 205
3-518 510
4-340 275
5-338 280
6-216 210
7-458 450
8-
9-
10-
11-512 510
12-222 195
13-338 280
14-

[DaveWM]

G2
11-630v
7-680v
3-720v

G1=2,6,12 200v

K= 4,5,13 310v

is what I show as correct on the RCA filed service guide

[Eric H]

I was using the Sams for mine, it does show the screen controls connected to the 640 volt Boost, I guess I need to check that and see what i have.

[Eric H]

Okay, I have 680 volts on one end of the screen pots and I can get between 385 to 680 at the CRT pins 3, 7, 11 depending where the pots are set.

[Eric H]

I moved the set to a safer location and swapped in the new CRT, while it did make a big improvement it still isn't right.

I have to put the tuner between channels to get a decent picture, if I put it on ch 3 and try to fine tune it I get a lot of distortion and interference, I also note that the brightness jumps up and down so I'm wondering if the AGC is causing a problem, I set it at a point where it gives the best picture, more and it gets to contrasty, less and the picture disappears.

With the color turned up the bars look pretty good, turn off the color and everything on the left disappears, I think it's just not bright enough or too contrasty to see.
It looks pretty good on a solid color like the DVD splash screen or the bright scene with Shirley Jones, but notice how dark objects have no detail at all.

At least I know my new 21FJ is good! I got the purity and convergence pretty decent for having spent all of a minute on it.

I guess I will continue to recap the chassis and see if it improves, it's full of Maroon drops and those do cause issues in B&W sets not too much older than this one, I bought all the Electrolytics for it also, dreading restuffing those but no choice since there's no room below to put them.

[DaveWM]

super critical AGC was a bad agc filter cap on a set of mine. Scoping the agc will show this. a .1 cap is a filter. I had a LOT of bad maroon caps on my CTC-9

[Eric H]

Finally some progress!

I finished replacing the film caps and restuffed one of the cans shown in the pictures below.

This had a major effect on the picture, it's no longer too dark and contrasty and the AGC control responds much more smoothly.

The Drive controls still have no effect though and to get acceptable brightness I have to have the Screen pots turned up to maximum.
In the service position however I have to turn the screens down or the three color lines are way too bright so perhaps there's something wrong in the circuit around the service switch?

Also there is a lot of herringbone in the picture and I can't get good picture and good color together at the same time, it no doubt needs an alignment since I swapped out the entire i.f. board and replaced the three video i.f. coils.

[old_tv_nut]

My guess: Usual advice is to do alignment after everything else has been tried, but I think in this case since you replaced all the IF coils you definitely need the alignment. That might change the video level completely and fix some of your problems with picture levels not matching setup levels. Would also have a lot to do with sound and color problems.