a buddy got a CTC-21 combo, nice style cabinet power tuning (vhf goes down vertically). has a decent SS tuner amp that the TV audio goes thru, which is nice. Speakers are a HUGE oval must be 15" by 9" then a mid and a couple small tweets, no horns though.

short on vert about 2" tried a new tube, but my guess is a open cathode bypass cap.

at 1st it had very low contrast and no color. I sub in a few IF and video amp tubes and got a decent pic, better but still lower on contrast than should be. I did not try a new RF tube (nuvistor), but I figured it was ok as there was no snow.

color would rainbow, after trying several 6GH8's I was able to get a color lock but not sure if its permanent (would go out of lock then I would sub some more 6GH8's and it would come back).

CRT was weak on all guns (one gun was just in the good, the others were in the bad on a CR-70 sencore), has a real bad cateract, (molding, brown etc..)
worst I have seen.

25AP22. I picked up a 25VDEP22 today, got home and duh it was a NOS but had a bad cateract (I did not even check) oh well. I am not sure it would fit anyway since I think the 25A is really a 23v size. The 25V I got tested very good for emissons and cut off and tracking. Maybe someday I will try my cat removal skills on it, but for now its going in the attic.

The plan is to replace half dozen or so eletrolytic caps (not the cans, I will test them 1st) and then check around that 6GH8 tube for out of spec resistors. I suppose it could be a weak crystal, but the resistor check out is easy.

if anybody has a 23v they would like to part with, let me know. This guy really wants to put the new tube in it, and I am not real sure I want to try a rejuv unless I have a backup tube.

I think I really hooked him on the retro tv after he came by and saw my meager collection.

Did you try cooking the filiments on 8volts overnight to see if the tube comes back. Some of your low contrast issues could be attrubited to a weak CRT.

25 inch tube without the "v" are 23 inch tubes.a regular 25 inch crt is a 23v.i have a 23v crt i was saving for something later on.go ahead and give it a light hit.its an rca-they seem to restore easy.good luck!

well I went thru it all but one of the ecaps tested fine, I was sure the vert size was going to be a weak bypass cap. Oh well. I tested the .1 coupling cap from the vert osc to the vert out, tested good. I know the lineairity adj can interact with the height (at least on some sets) so I will try adj that a bit to see if I can fill it in. the only issue is the space is on the bottom of the set and IIRC lin generally streatches the top.

I did not check the voltages but will do that when I put the chassis back in the set.

The was one weak ecap section a 50uf off the AGC center lug pot. it was about 10uf (can marked 50uf) since it was not leaking I just tacked a 47uf on and will see if that effect the contrast any.

I have a CTC service manual, but if anyone has a Sams with resistance readings I would appreciate a scan of that sheet.

I did find one stake near the 6GH8 tube that was loose, perhaps will account for the intermittant color sync issues.

there was also a NP 5uf cap in the pin cushion circuit that I tested (looks like a Ecap) with a very high power factor on the eye tube cap tester. But since the pin cushion looks ok I just left it. I have a couple more 6GF7 tubes (dual triode vert osc/vert out) that I could try if the lin adj does not pan out.

I was kinda shocked to find all those tube ecaps to be in good shape, I expected them to be leaky but all test ok.

one thing that looks a little fishy is the vert out tranny, looks very toasty. It sit next to the HV regulator tube so I dont know if that tube gets hot enough to toast the tranny or if the tranny may have gotten hot enough to short a few windings (and there by cause the reduced vert height, geez I hope that is not the case).

Check a 100 ohm resistor goes between the vert height and vert Lin pot. It's a 1/2 ohm. It might be a 150 ohm. Ii bet it's bad

could not find the 100 ohm resistor.

Need some one to check the Pin 3 of the 6GF7 that is the cathode of the vert output. The resistors in the circuit do not match up with the value installed. I have a 330 where a 68 should be, the total resistance at the tube is 1.6k

It looks like the vert uses boosted voltage off the fly. There is a diode in there that did not reg on my diode checker, perhaps its just a HV diode that the DMM cant check. I tested the forward and reverse res 2 meg one way 2.7 meg the other, but that is in circuit.

well I went ahead and popped for a new vert out tranny, so JIC that is the problem I will have one handy.

found something interesting that may have been a cause of the vert. Granted I was not able to check the voltage at the plate of the vert out, but I did trace the primary windings back to its source of B+. There is a big 600 ohm resistor looks like at least 18 watt right off the hot side of the choke (420vdc). this resistor is what drops the 420 down to the 370vdc for the vert plate load thru the primary. Well the wire from the choke to the resistor was nice and green and toasty, and did not even seem to be well soldered (I was able to pull it thru. I am guessing there was a voltage drop right there. I replaced the wire, cleaned up the term strip fluxed and soldered it back. Maybe I will get lucky on this one.

Look for the broken wire before anything else....

I remeber working on my CTC-17 and the wires were corroded from the terminal strip off that choke. Same as you are describing. I had full vertical collapse. Might be on to something. I had to create a new terminal strip and replace a few wires.

I remeber working on my CTC-17 and the wires were corroded from the terminal strip off that choke. Same as you are describing. I had full vertical collapse. Might be on to something. I had to create a new terminal strip and replace a few wires.

hope that does it..

:yes:

I replaced the short wire off the choke, then wire brushed the heated solder on the term strip. there was another wire going off some where that was toasty, i cut off a short pieced, scrapped the oxidation off and was able to get a decent joint (I think). I may end up doing as you did and replace that other lead, I think it went off to the PW700 board, but I lost track of it.

That area gets mighty hot and the plastic shielding on the wires really becomes corrosive to the point where the metal breaks and becomes super brittle. Nasty situation. Resolder all the ground lugs on the chroma board. That caused my intermittant color issue.

re soldered the ground stakes, clipped and replaced the 400v B+ lead to that resistor (actually only clipped about 2 inches worth replacing the brittle burned part). Not sure if I need to bother with those filament lead wires that run on the top of the board. I see some green, but I may just try it as is. Its not my set so I would like to see where it is now. I did replace one other resistor on the chroma board, it was a 470k 10% that was at about 520k, not much off but its leads were green with ruff corrosion. I just did not like the way it looked. Hooking it up tomorrow, will zap the crt and see if it looks any better.

Good luck! Sounds like you hit the critical areas..

Vert and contrast cured. guess that B+ wire was the issue, and i assume the contrast was an AGC issue since that is where I replaced a weak electrolytic cap.

New problem, Lack of blue. I went ahead a zapped the green and blue guns, emmissons are fine now. but the blue seems to have gone away (it was there before the zapping). Its not completely gone but not much, however it did seem to be coming back just as I was leaving so I told him to leave it on for a few hours.

in the service posistion I have to turn the kine bias all the way up and the blue screen all the way up to just barely get a blue line.

I guess the zapping may have effected the cutoff setting (I dont recall if it changed before and after the zap) Used a sencore CR-70 in the auto mode.

I ran out of time to check the pins at the crt for voltages. I was thinking maybe one of the bias resistors off the kine bias pot (3 1.5 meg resistor one for each gun) may have driffed.

Also color lock is still unstable, rainbows, if I turn up the voltage above 120 it will lock, but regular line voltage its iffy. I have a bag full of 6gh8's that i can try subbing, and I have some spare 3.5795 crystals that I may try. But before I do all that I will check the voltage at the tube pins. Just ran out of time.