CTC 7 advice needed

[droptop]

Hey everyone. I’m looking for guidance with my CTC 7 so I thought I’d ask the experts. It’s fully re-capped and displaying a picture with a visible drive line. None of the usual horizontal adjustments will remove it. With the brightness control turned completely off I have a picture much brighter than it should be and out of focus. I found that all the screen controls had been turned fully on. After some approximate adjustments following the instructions good focus is still unobtainable even with 22 KV registering on the CRT. The set has new HO, HOT, damper, regulator and HV rectifier tubes. I’ve also replaced several resistors that were off value in these circuits. What I need is advice on what to expect the brightness control to do and where to start with the setup. I have the service literature outlining the horizontal sweep adjustments. Can or should these steps be performed with the brightness issue unresolved? Were the early color sets designed to go completely dark at minimum bright/contrast settings? Thanks guys.

[Zenith26kc20]

I would check the voltages at the cathodes and control grids on the picture tube. The CTC should go dark with brightness and contrast at minimum. Do you have retrace lines?
Check the low side of the screen controls also. I don't have my schematic for that chassis here at work. Does it have CRT bias and if it does, is it adjusted properly?
Chek the drive to the horizontal output tube but be careful, there is a good bit of signal on that grid and it may give some of the newer digital voltmeters a bad time and mess up readings.
I use a VTVM on the older sets. It stops me from buying new meters over and over.....

[Zenith26kc20]

Did more research last nite. I looked at a CTC 9 so the info may be a bit off. First, remove the CRT socket and turn on the set. If the high voltage comes on OK, the tube is saturated and drawing too much current.
If this is the case, check all voltages on the color output plates (6FQ7) for around 350 volts or more. The cathodes must be a good deal more positive than the control grids (grid #1) to cut the tube off.
If HV is still low,
Check all connections around the flyback and look for a capacitor on the flyback off value. I recently went thru my TS-14 Motorola and found a .005 mfd new cap at .008 mfd upsetting the vertical. keep us updated

[droptop]

Thanks for the information. I spent the better part of the evening going over the chassis and found a number of resistors that had been replaced long ago in the blanking stage- none of which were the correct values. Once this was corrected the brightness control action now seems correct and the HV adjustment now functions. The schematic indicates 20.5 - 21.5 KV. At that setting the focus still seems soft but the convergence is a bit off which might be part of the problem. Also there is a drive line in the raster about 2 inches to the left of center screen and the video is squeezed quite narrow but not folded over. The H-linearity control alters it slightly and at one setting causes the line to go black with a gap in the raster. With minimum drive setting it’s still visible in the photo. The width adustment (swapping leads) at the yoke has no effect on it. The wave form is correct off the plate of the HO and at the grid of the HOT. Socket voltages of the HOT, damper and regulator agree with the schematic. Ideas?

[marty59]

Is that just a bright line or is there some foldover within that line? Could still be damper/retrace related..

Is the horizontal linearity still a problem too? Can you display a round (like a B/K Analyst) pattern? See if you're getting any "pie crust" effect.

Just to be on the safe side, make sure your HOT current is ok.

[Zenith26kc20]

It looks like there is a small amount of insufficient width on the left side. Check the ceramic caps in the damper circuit.
What is the negative voltage on the control grid of the horizontal output tube?

[David Roper]

I had a black and white set with very similar horizontal symptom. Turned out to be a shorted width coil.

[old_tv_nut]

just a dumb question - have you tried more than one new HO tube and damper tube?

[droptop]

Interesting. I have tried another damper tube but will have to locate another HOT. Replacement of the caps in the yoke made no difference.

[Zenith26kc20]

was looking at notes on my schematic. Has this sets flyback been replaced by an aftermarket? My notes show "use RCA only flyback" on them. I do remember CTC11's being picky also.
Also, does the flyback get hot?

[droptop]

The flyback appears to be the original. This is a low hour set and the overall condition of it seems to indicate that to be true. The flyback doesn’t overheat- runs just warm to the touch after 30 minutes and shows little wax leakage- certainly looks normal compared to many I’ve seen. The insulating tire is clean and soft where they usually harden with heat. The high voltage indicated for the CRT is easily obtained and regulates well within rated cathode current for the regulator and HOT. The resistance of the winding feeding the yoke measures 7.2 ohms. The schematic indicates 9.4. Anyone out there with a flyback they would loan for sub purposes? The RCA part # is 106359 and the following numbers were found on the flyback itself- 1106862-2 and 274825.

[oldtvman]

try replacing the horz output tube and damper tube.

[old_tv_nut]

A thing of beauty, indeed! Congratulations!

[jr_tech]

Very nice!
Another lovely vintage color brought back to life... was the '7 the first RCA color set with remote?
jr

[holmesuser01]

Nice color on that set.

Bewitched always looks great on a roundie.