CTC-7B Basket Case

[sean]

I got this rough CTC-7B from RobtWB a couple of years ago. The original thread about this set is here:

http://videokarma.org/showthread.php...highlight=ctc7

I finally got around to starting on it a couple of weeks back. I had done a preliminary cleaning when I first got it and checked the flyback and the CRT at that time also. Both checked out fine. I started out by re-stuffing the electrolytics and replaced the paper caps and bad resistors in the horizontal and vertical sections as well as the HV section. Last week I powered up the set with the vertical and horizontal output tubes removed just to make sure I could get B+ and get the horizontal oscillator working. Today I hooked the chassis up to the CRT and yoke and slowly brought it up on the variac while monitoring both the line current and the B+ voltage. I was able to get a raster on the screen.



I checked the HV and was getting about 10kV. Adjusting the HV ADJ pot made no difference except when set at one particular spot the voltage would jump to about 20kV. I pulled the chassis again and found the HV ADJ pot was open. I replaced it and powered the set up again. I could now adjust it for a pretty solid 22.5kV regardless of brightness. I thought I would the set up to the cable TV source and see if I could get anything. After fiddling with the tuner I was able to get some images to start coming through but no sound.



I still have a lot of capacitors to replace and resistors to check but at least the set is coming back to life.

[Sandy G]

Kewl! Another old veteran coming back to life !

[bgadow]

This is the fun part! Really great to see that first raster, no matter what it looks like.

[Tom S]

When it's all done and you have your sweat and blood in it, sit back have a beer and enjoy your Tv.

[ceebee23]

oh nice ..very nice indeed!

[Kevin Kuehn]

That's very inspiring seeing that one come back to life.

[RobtWB]

hello mr. sean
happy to see that beast with a raster and
happy to see you have brought it back from the grave ... i simply do not have the patience to tackle an electronic restoration of that magnitude ...

[Sandy G]

You ain't quite "There" yet....But you're gettin' CLOSE ! Another "Glorious Lollipop Color" set...Hehehehehehehe...

[hi_volt]

Excellent! Pretty soon it will be ready for another 50 years of service. Love seeing them come back to life.

[DavGoodlin]

There is nothing like a top-quality color RCA lighting up, step by step, all colors showing...

Go slow, lotsa caps and wires to cross, er check

You fix this one, you can fix anything!

[sean]

I have made some progress on the set in the way of replacing capacitors and resistors but it has not improved things. I have all of the boards finished but have not touched the color section of the chassis. The height of the raster is low, even more so now than my photos above show. I have found that the B+ Boost voltage is low (about 700V when it should be around 820V). The B+ line is about 35V low (350V when it should be 385V). It's probably leaky caps causing this so I'll keep chugging along at replacing caps.

[sean]

Well I have suffered a setback. I was finally able to get a somewhat stable picture on the set. I was adjusting the R,G, & B screen and background controls to try to get the color looking better and noticed that the blue never changed. I pulled the chassis out of the cabinet to finish the recapping in the color section and decided to test the CRT again. Now the filament for the blue gun does not light. I tried re-flowing the solder in the filament pins of the base but it makes no difference. So, does anybody know if the filaments in the 21CYP22 are all connected internally or do the individual filaments come out of the glass and connect together at the base pins? If they are connected internally then this tube is now shot.

[Eric H]

They are connected in parallel inside the tube, if one is out it's not repairable.

[DaveWM]

I had hoped that tapping around the neck while moving the tube around may cause what ever happened to reconnect. I never had any luck with that. On my 21CYP22 it was the red that did this. I still have the tube as 21CYP22's are not common, and the hope is some day to get it rebuilt if a CRT rebuilder ever comes back.

[zenithfan1]

That sucks about your CRT, do you have a 21FBP22 to put in there? The rare earth grey face ones look better than the green sulfide ones do in this era of set, although either will work. Good luck, it's getting close!