View Full Version : CTC-5 No luminance.


OS X
01-24-2016, 10:37 AM
I just bought a restored CTC-5 and I'm having a problem with it, I'm getting no luminance but good chroma. I don't know much about color sets so I'm trying to get a idea what might be causing it? The CRT is good so I don't think it's anything with that.

dtvmcdonald
01-24-2016, 10:45 AM
There is both chroma and luma drive in those pictures, in approximately
correct ratio. The CRT screen and brightness and drive (per color) adjustments
just need correct adjustment, assuming of course that nothing broke between
restoration and your buying it.

OS X
01-24-2016, 11:00 AM
There is both chroma and luma drive in those pictures, in approximately
correct ratio. The CRT screen and brightness and drive (per color) adjustments
just need correct adjustment, assuming of course that nothing broke between
restoration and your buying it.

Thanks :) and I'm hoping that's all it is. I guess I need to start with feeding it a direct signal from a DVD player or I might even try and get a signal pattern generator. For how good the CRT tests I do have the brightness and contrast turned up pretty high to get that picture I wouldn't be surprised if the drive controls got bumped somewhere along the line. Also here's a video of it https://www.youtube.com/watch?v=EY3R3IIlJas

SwizzyMan
01-24-2016, 11:25 AM
Check the delay line or the 12by7a tube or parts associated with it.

OS X
01-24-2016, 12:13 PM
Check the delay line or the 12by7a tube or parts associated with it. I believe this set has all its original tubes so it very well may be weak. I guess if I can get my hands on a NOS 12BY7A I'll give that a try to start. Also does anyone have the service manual for this set they would like to sell?

Kamakiri
01-24-2016, 12:17 PM
I gots NOS 12BY7As :)

Electronic M
01-24-2016, 02:23 PM
I believe this set has all its original tubes so it very well may be weak. I guess if I can get my hands on a NOS 12BY7A I'll give that a try to start. Also does anyone have the service manual for this set they would like to sell?

Might be time to buy a tube tester.

Kamakiri
01-24-2016, 04:46 PM
Pretty sure he's got one, but I don't think it does many of the post-1960 tubes. We have to get together anyway, he has a GE color portable for me from his recent trip to Detroit :)

oldtvman
01-24-2016, 08:59 PM
That should be fairly easy to trace down with a scope. Straight forward video problem

OS X
01-24-2016, 09:49 PM
Might be time to buy a tube tester. I do have one and its a rapid tube tester model 82A it pretty much only tests emissions but works ok for a low end tube tester, After looking online for around a hour today I found the tube setup list for this tester as mine is missing at least 1 page and sure enough the 12BY7A is on there, I tested it and it is weak it's on the hi end in the middle questionable area on the tester. I'll try to test all the tubes in this set the tester supports :)

I gots NOS 12BY7As :)

Look's like the CTC-5 will need one :) I was able to test it after all and the 12BY7A test weak. And I'll bring your GE over for you as well :) I got side tracked with the last minute road trip to get the CTC-5 and didn't do much of nothing this past week Lol.

That should be fairly easy to trace down with a scope. Straight forward video problem unfortunately I don't have a scope :( I'm still building my collection of test equipment, right now I only have the very basics. Hopefully a new 12BY7A will help, If not I guess I'll have to get a scope.

old_coot88
01-25-2016, 01:39 AM
I just bought a restored CTC-5 and I'm having a problem with it, I'm getting no luminance but good chroma. I don't know much about color sets so I'm trying to get a idea what might be causing it? The CRT is good so I don't think it's anything with that.
Just to make one point clear: Luminance or 'Luma' refers to the B&W video component of the picture. That is, if you turn the color completely off, there'll still be a normal B&W pic.
Luma doesn't refer to brightness of the raster itself.

miniman82
01-25-2016, 08:35 AM
Though if the video (Y) amp tubes are weak, a dim raster can be a symptom.

Kamakiri
01-25-2016, 08:47 AM
Look's like the CTC-5 will need one :) I was able to test it after all and the 12BY7A test weak. And I'll bring your GE over for you as well :) I got side tracked with the last minute road trip to get the CTC-5 and didn't do much of nothing this past week Lol.

Test all the tubes in the sets you just got and tomorrow you can come shopping.

old_coot88
01-25-2016, 11:44 AM
Though if the video (Y) amp tubes are weak, a dim raster can be a symptom.
Right you are. :yes:

wa2ise
01-25-2016, 04:30 PM
All the unobtanium parts appear to be working fine (CRT, flyback, power transformer and such) and what is broken should be easily obtained.

OS X
01-25-2016, 06:16 PM
Well finished testing the rest of the tubes there's a fair amount that are weak. Both 5U4's are weak along with a almost dead 3A3, (2) 6AQ5A's,6CB5A and the 12BY7A. Unfortunately now there's a biger issue when I was removing the 6AW8 (and I was being very carefull) The tube socket just crumbled into pieces :( it was the only tube in the set that already was replaced, being it is the tube directly next to the 5U4's I'm guessing the extra heat did not help it.

SwizzyMan
01-25-2016, 06:24 PM
Those cheap phenolic thin wafer sockets do not like heat. Gets to a point when no matter how gentle you may be they are just too brittle and they break.

miniman82
01-25-2016, 07:02 PM
You can still get PC mount tube sockets on eBay.

Electronic M
01-25-2016, 07:22 PM
I've had sockets where a few pins no longer were in contact with the remaining phenolic....I was still able to plug tubes into them and have the set work fine.
Electricity don't care how good something looks or how complete the mechanics are, as long as the paths it is supposed to follow are conductive and the ones it is not supposed to follow are not conductive, it will keep flowing the same way it has for decades.

Just be careful not to bend the socket contacts when removing and inserting the tube and it should be fine.

Arcanine
01-25-2016, 08:39 PM
Well finished testing the rest of the tubes there's a fair amount that are weak. Both 5U4's are weak along with a almost dead 3A3, (2) 6AQ5A's,6CB5A and the 12BY7A. Unfortunately now there's a biger issue when I was removing the 6AW8 (and I was being very carefull) The tube socket just crumbled into pieces :( it was the only tube in the set that already was replaced, being it is the tube directly next to the 5U4's I'm guessing the extra heat did not help it.

3A3 tubes always test bad. The testers don't generate the voltage that goes though those tubes. It's still good. Don't sweat it. Get a spare, yes, but even NOS will test bad, too.

OS X
01-25-2016, 09:37 PM
Thanks everyone :)I'll probably get a new tube socket being there still available. How hard are they to replace? My soldering skills are not all that good yet but I have worked on replaceing caps on a few B&W sets before.

Electronic M
01-25-2016, 10:09 PM
Thanks everyone :)I'll probably get a new tube socket being there still available. How hard are they to replace? My soldering skills are not all that good yet but I have worked on replaceing caps on a few B&W sets before.

Unless you have a 70W+ soldering iron AND good solder sucker (or have mastered the tricky art of using solder wick) don't bother replacing it....You'll just end up lifting the traces and messing it up real bad. Socket removal is not easy with a good iron and sucker, and becomes a royal pain with out both on hand....I only do a socket change when I can no longer clean a socket's contacts, it's gotten too damaged to use, or I've tried everything else to fix an intermittent associated with a tube.

dtvmcdonald
01-25-2016, 10:30 PM
Another idea, if its not an RF tube, is to install a socket saver in the afflicted socket,
and leave it there forever. That's expensive, but this is a reasonably valuable set.

old_coot88
01-25-2016, 11:44 PM
... The tube socket just crumbled into pieces :( it was the only tube in the set that already was replaced, being it is the tube directly next to the 5U4's I'm guessing the extra heat did not help it.
If all the lugs are still solidly in place, couldn't you fill in amongst/around them with some silicone?

andy
01-26-2016, 04:59 PM
I agree that it should be fine as it is, but if you do replace the socket, break up the rest of the phenolic and remove one pin at a time. After the pins are out, you can remove the solder and install a new socket.

Electronic M
01-26-2016, 07:47 PM
I agree that it should be fine as it is, but if you do replace the socket, break up the rest of the phenolic and remove one pin at a time. After the pins are out, you can remove the solder and install a new socket.

If you do that be sure the solder terminals match up with the ones of the original that go through the board (i.e. make SURE it fits) before you crunch the old one....Otherwise you may temporarily be SOL.

Kamakiri
01-27-2016, 06:32 AM
Welp, he was here yesterday and we tested his tubes. Shunt regulator was dead as a doornail. I think 5 or 6 tested weak. Hooked him up with all new tubes. Hopefully he'll report back in when he makes further progress.

miniman82
01-27-2016, 07:52 AM
Welp, he was here yesterday and we tested his tubes. Shunt regulator was dead as a doornail. I think 5 or 6 tested weak. Hooked him up with all new tubes. Hopefully he'll report back in when he makes further progress.

Not that it needs a 6BK4 or anything, they struggle to make HV even with it disconnected. Hopefully he checks the HV with a probe to make sure it's not running too low, a 5 with a dead regulator is an unlikely situation.

Kamakiri
01-27-2016, 08:09 AM
I was puzzled by that too.....

OS X
01-27-2016, 02:38 PM
I'm finishing up recaping a B&W RCA set first, I'm 95% done with that I'm just short 2 caps I forgot to get, once I finish up that I'll get back to the CTC-5 :)

ChrisW6ATV
01-28-2016, 02:55 AM
I'm just short 2 caps
People have called me "a couple of capacitors short of a whole TV set" myself. :D

OS X
01-29-2016, 12:28 AM
Well bad news with the CTC-5, put all the new tubes in it put everything back toghter powered it up with the variac running it at 115V and got sound and the 6AW8 was glowing so I'm assuming the tube is making contact. But now the big thing is NO HV I let it run for a minute and nothing so I went to get alittle closer to the HV cage to see if I can hear the HV and just as I was going to do so two big flashes came from it talk about a scare! I jumped back and immediately unplugged the set, nothing looks fried and filter caps and transformer where still cool I double checked everything and all the tubes are right and every thing is in place. I'm pretty sure this set hates me! I just even bought a NOS channel selector knob for it I'm into this set for around $500 now with not much to show. At this point I would be willing to trade the CTC-5 for a good working later round screen color set. I like the 5 but it's becoming 1 issue after another Lol :(

rca2000
01-29-2016, 01:01 AM
If I am not mistaken...the 5 has an un-pluggable anode lead...I THINK it plugs into the HV rect socket. MAYBE..that has become loose...and arcs every once in a while. Such would explain BOTH the flashes and the NO hv problem !!

OS X
01-29-2016, 01:09 AM
If I am not mistaken...the 5 has an un-pluggable anode lead...I THINK it plugs into the HV rect socket. MAYBE..that has become loose...and arcs every once in a while. Such would explain BOTH the flashes and the NO hv problem !!

Already checked that and it's not loose, The set was on for around 2 mins before the flash so the HV should have came up before then :( also it was only drawing around 200 watts from what the kill a watt meter says, when it was working with hv before a few days ago it was useing close to 300w.

Electronic M
01-29-2016, 01:22 AM
If you changed any horizontal/HV tubes just prior to that power up try going back to the previous set.

Color TVs don't like to go a year without malfunction under regular service, that is life.

OS X
01-29-2016, 02:00 AM
If you changed any horizontal/HV tubes just prior to that power up try going back to the previous set.

Color TVs don't like to go a year without malfunction under regular service, that is life.

All of the tubes got changed in the HV area the old ones where weak or completely bad. And that's understandable I expect some problems but just not evey single time I turn on the set Lol

Kamakiri
01-29-2016, 03:40 PM
Welcome to early tube color television ownership :D

They're like old cars. You have to expect everything to break or go bad until all the marginal parts are replaced.....sometimes you don't see them till it's getting used regularly.

miniman82
01-29-2016, 10:11 PM
Ditto. A lot of the time the trouble is with the horizontal section, because it's got the most stress to deal with. But once you get it straightened out, they run for years.

Electronic M
01-30-2016, 02:27 AM
All of the tubes got changed in the HV area the old ones where weak or completely bad. And that's understandable I expect some problems but just not evey single time I turn on the set Lol

It don't matter if the tubes are bad! If last time it worked was with those bad tubes PUT THE BAD TUBES BACK IN and see if you get it to produce HV. If it works with the bad tubes back in then try the "good" tubes one at a time powering up between each one, until it don't work. The last good one put back before it craps out is a bad tube....If it don't work with the old bad tubes or the good new ones then the problem is likely elsewhere. The horizontal stages put voltages and loads on tubes that NO tester comes close to accurately approximating so NO tube tester CAN tell you with certainty that any horizontal tube is 'good' or 'bad'....All a tube tester can do in the case of horizontal tubes is give you a crude qualitative guess as to good it is.

miniman82
01-30-2016, 12:19 PM
Exactly. Ever a mutual conductance tester that actually passes some current though a tube won't tell you how it will behave in a given circuit, frequently a tube will work in one circuit well and fail miserably in another. Hence the expression 'tube rolling'.

ChrisW6ATV
01-31-2016, 01:41 AM
I think I see a couple of wax/paper capacitors in your set's HV box. Those should be replaced before other tests are done.

DaveWM
02-03-2016, 09:28 AM
what the others said (use the old tubes, replace those paper cap in fly cage) AND check the fuses. also use the correct fuses if not already doing so.

consoleguy67
02-03-2016, 11:24 AM
Oh, what a frustrating and rewarding hobby we're in.

OS X
02-04-2016, 11:43 PM
Well took a break from working on this set, before I did I got HV to come back although still have to measure how much HV it's putting out, unfortunately no raster but that may be due to the bad tube socket as I believe it's a video amp tube. Going to replace the wax caps in the HV cage before anything else, I believe I found someone with an extra tube socket that will work I just need to wait for it to get here before I start working on it again :)

Hagstar
02-08-2016, 11:31 PM
Hmmm- interesting. I got into early color sets for the same reason people get into British cars- style, certainly not reliability. My first mentor made me SWEAR I'd never leave the room while a CTC7 or earlier was running even for a moment. My CTC4 draws an arc at the drop of a hat. It took me years to build up the courage to tackle it. One slight error in wire dressing- ZAP!

SO I suppose part of it is one's point of view. These sets should probably not have been sold until 1960 is mine. I have vivid memories of our Zenith's flyback in flames even in 1968. Perhaps that prejudiced me.

John H.

Electronic M
02-09-2016, 01:36 AM
Zenith flyback failure (aside from the 1948-1951 portholes) is fairly rare let alone a flaming burnout.....It's like getting hit by lightning on a sunny day.