Hi folks. Here are the first pictures from my CT-100. Still need convergence and purity but I do have video. The color lock problem I noticed on the scope reported earlier turned out to be a bad ceramic capacitor in the burst oscilator.

I also lost the 275 volt line during troubleshooting and found that the field Neut. pot protected my newly added fuse. 275ma should not have been a problem for a 30 ohm 3 watt pot. I had it fused at 315ma. I disassembled it and soldered over the break. It has run Ok since then so I am not sure what caused it to fail. I tried to locate a replacement and tapped pots are just not made any more. Hopefully it will continue to function.

I also had a 6AN8 tube fail while the chassis was on the bench. 5th IF. The Pentode section just quit conducting. Filament is OK. I, of course, initially thought some component went bad. Luckily it was just the tube.

I found that most of the dag came off of the CRT so I had to replace it.

I also uploaded a photo of a service tag from 1956, half a century ago!

In the short time I have played with the set tonight after I got it assembled, I cannot get the Red purity to come in as it should. The manual states that the purity coil should be 1/4" from the tube base but I have to have it up against the yoke to have any kind of decent red field and it is still not that good. Any advancement of the the purity control away from full CCW just makes it worse. Not sure yet if I have just not found the sweet spot or if I have a problem. I'd be interested in any experiences in this area.

It is great to see this old girl running.

Tim,

I have some NOS 50 ohm CT pots, if you want one let me know.

Chuck

Wow ! An' ANOTHER one rises from the dead...Great !

The manual states that the purity coil should be 1/4" from the tube base but I have to have it up against the yoke to have any kind of decent red field and it is still not that good.
Congratulations Tim.:thmbsp: My own static convergence/purity assembly clamp sweet spot is 3/4-in. from the tube base, which puts it pretty close to the yoke. Also a reminder. Make adjustments by rotating the black disk while holding (if necessary) the mu metal shield assembly clamped to the tube neck in its proper position (blue static convergence magnet up).

Thanks for the offer Chuck. I'll keep that in mind. Thanks also to Terry for sending me those peaking coils.

I appreciate the advice Pete. I realized that after a while but it still did not seem to be working as it should. Question on the orientation - is the access hole for the clamp on the left? That is where the manual says it should be and where mine is but I saw a photo of a set with it on the right.

I'll get back on it tomorrow or Saturday. We had the family over tonight for Thanksgiving and I learned long ago that alcohol and High Voltage do not mix well. :yikes:

Mine is on the left also. The braided lead seems to be long enough to be dressed over to the right as well. Doesn't matter. Just so one of the static convergence magnets is straight up (that'll make it the 'blue' magnet).

For purity adjustments, I pull the field neutralizing coil plug (three prong) rather than center the pot. And as a reminder be sure you have the yoke back as far as possible.

Hi folks and thanks for the coils Terry.

The repaired field neutralizing pot seems to be holding OK.

I have had some time to work on it and I resolved the purity problem. I discovered that when I installed the fuse I had put the coil wire on one side of the fuse and the pot on the other. The potential difference across the 3 ohm fuse meant that there was always current flowing through the purity coil, even when the pot was full ccw. Moving the wire allowed the purity to be adjusted. I have to remove the CRT again so I did not dial it in 100% but it is very good.

Then I went on to convergence and I found that, after much twiddling, I cannot get the top and bottom as close as I would like. Blue will not converge with the green and red. I have attached a shot of what it looks like. I also have to have the focus control full CW and feel like i'd like it to go a very slight bit more. Focus voltage is 3kv at this setting. I'd be interested in others experiences in this area.

The only other major issue is that depending on content, the HV swings from about 16KV to 20KV. The focus voltage sometimes drops to zero when the HV is minimum and the screen becomes a massive blur. It then recovers when the screen content becomes darker. The focus and HV regulator tubes are NOS and the HV shunt regulator tests good but I do not have another to sub it. Could this be possibly caused by driving it direct from cable and the front end is being overloaded? The test generator also causes this same problem. I have not yet tried another source. Any comments on this phenomena would be appreciated.

The set is very watchable from a distance and I am pleased with the progress so far. I have attached some screen shots. My camera is not accurately displaying the color of the bars though. The Yellow looks more yellow on the screen and the blue is darker than the camera shows. I also cannot see the moire' on the screen that the camera is picking up.

Tim,

Congratulations!

Convergence is a tricky business, as I am sure Pete can tell you. You may know this, but you will find the static and dynamic convergence portions of the procedure tent to be iterative. Once you have done static then dynamic convergence, go back and re-tweak static and then dynamic convergence. You may iterate to a better solution. I assume you have degaussed the set? If not, this may also help with purity and convergence.

The HV performance on the CT100 is always a bit disappointing. When it "blooms" and gets a dark screen with a fuzzy blob, it is an indication your HV supply is overloaded. Reduce the brightness and contrast to a lower level. The tendency is to turn up the brightness and contrast for a good picture, and then when a scene comes with lots of white content, the HV supply cannot meet the demand and the HV and focus drop out of regulation. I do not suspect there is anything wrong with the set, just the irresistible temptation to turn it up a bit too much.

I wonder if this one has a new CRT or a good old one. I guess we still can't rebuild the 15G?

I wonder about those other '54 models that have been discussed here like at least one Motorola and one Zenith. It would be great to see those three sets all working for picture quality. I am guessing they were all pretty equal.

Does anybody have any stories from people who actually had one in '54?

Tim,

Kudos on an outstanding job of troubleshooting and bringing your CT-100 back on line. I agree with John Folsom, that after all is done with convergence, purity set up and degaussing, 100% perfect convergence may still elude you. The moire effect is common with digital screen shots.

-Steve D.

Thanks for the comments guys.

John:

Yes, convergence can be tricky. I just was going around in circles on this with the few handles there are and not making it any better. It was concerning me that I was at the end of the adjustments, including focus, and have no more range. Is it typical for the focus to be up against the clockwise stop?

This HV issue I guess is normal but it is hard to believe it was that way when it was designed, that the owners could not turn up the brightness and contrast without a complete focus meltdown. My brightnes and contrast were set about 75%. Is this a component age thing or is it the belief that this was always that way?

Bobby:
The CRT is probably the original but it still has good emission. The date code of the CRT is the 26th week of 1954. Most of the other tubes in the set are dated the 12th week of 54.

Thanks Steve. It is always good to learn what is considered technically "normal" for a model set. If this is as good as it gets then so be it. Interesting that you mention degaussing as I was considering that but did not do it as this thing was sitting idle for so many years. I have to remove the CRT again before I set it up for good so I'll leave it as it is and try to walk it in better when I get it moved upstairs and degauss it. I guess degaussing would be regular maintenance for this set. Has anyone had any problems using a standard degaussing coil and procedure on a 15GP22?

Great work, Tim. Missed the fun earlier in the day cause I'm in Michigan for a grandson's first birthday.

As John indicated, convergence is something of a skill to be developed. Keep at it. As I see it, what you have will produce a good picture, but there is also room for improvement if you want to spend the time. As for the blooming. Join the club. :D I suspect that RCA/NBC showed off the Model 5's on Jan. 1, 1954 in a dark room to avoid the blooming thing and probably to eliminate reflections from all that glass. I've used a regular '70's-era degaussing coil on the 15GP22 but couldn't notice any particular improvement. I've noticed the resolution of the picture improve as convergence improved, as you would expect. But it really looks impressive, particularly when the source is a live sporting event shot with hi-def cameras, perhaps because, as old-tv-nut has indicated, the hi-def system standards specify camera matrix characteristics.

It's back to NJ for me tomorrow.

Pete

... re the focus control: no, it shouldn't be at the end of the pot of course. Could be the 50-meg resistor in series with the pot or, let's hope not, the vertical convergence transformer could be heading south. That 0.01-uF filter cap on the focus line has no doubt been replaced and therefor is not much of a suspect. To start with, I'd make sure the series string is okay.

*cries*

Glad you had a great time with your family Pete. Have a good trip back East. Thanks for the encouragement and the club initiation.

I appreciate the sentiment Fujifrontier. Hang in there, there is a whole lot of fun in the quest.

Glad you had a great time with your family Pete. Have a good trip back East. Thanks for the encouragement and the club initiation.

I appreciate the sentiment Fujifrontier. Hang in there, there is a whole lot of fun in the quest.

haha, i meant it in much the same vein as a toddler whose ice cream falls to the ground while there sibling munches happily away at theirs :rofl:

Tim,
The moire effect is common with digital screen shots.

-Steve D.

To avoid the moire efects, you'd need to photograph the TV screen at a much higher resolution. High enough that you actually capture all the RGB phosper dots. This also applies to scanners used to scan magazine ads. High enough resolution to capture individual halftone dots. Then using Photoshop or such, do a low pass filter, aka "blur" on the picture. Then shrink the image to the desired final size. Photoshop's shrink is usually preconfigured to do the blur before the shrink for you.

TV camera designers even in the old days had to worry about this. To avoid moire flicker (in interlace mode this really sticks out) they had the TV camera lens designed so it could never make too sharp an image on the pickup tube. The scan lines did a "digital sampling" of sorts of the image in the vertical direction. Have the image too sharp of say a distant window with venitian blinds and some of the slats would fall between the scan lines. And produce moire patterns that don't exist in the real world in person.

hmmm... so what would happen if we fitted a TK-41 with a modern day HD-grade lens? :P

hmmm... so what would happen if we fitted a TK-41 with a modern day HD-grade lens? :P


I suspect a "modern day HD grade lens" is nothing more than a specific style of lens available way back. I don't think modern lenses were any different than the lenses specially designed for the TK-41.

It is really neat to see special stuff like that when it looks so new.

That is wild that the tube is in such great condition.

Has it had that sealer applied to the metal/glass seam?

Could you tell us about the sets history? I guess someone used it for awhile and put it away for years. It would be very interesting to know why it had little use and how you came apon it.

Perhaps it is in another thread?

It must be a very special sensation to be in charge of something so special.

I suspect a "modern day HD grade lens" is nothing more than a specific style of lens available way back. I don't think modern lenses were any different than the lenses specially designed for the TK-41.

well the reason I asked was because w2aise said
they had the TV camera lens designed so it could never make too sharp an image on the pickup tube

and i thought perhaps todays lenses werent like that

Yes, the vac-seal product has been applied to the seam. It is amazing that some of these CRTs are still good but many have gone to air. It could partially be related to the environment in which they were stored. I believe this set was always kept in a controlled environment where there would be minimal expansion and contraction due to extremes in temperature. I am sure there are a number of factors involved, even the day of the week it was made and the exact manufacturing tolerances of the components.

I do in fact know the history of this set, which is an interesting component of any historical item. I am the third owner (custodian) of it and one of my sons will be the 4th. It was originally owned by Budd Lynch who was the radio announcer for the Detroit Redwings and I believe is now the PA announcer for the team. It had at least one service episode as can be seen on the service tag I posted earlier in the thread. This was in 1956 when there was no vertical sweep. I saw no evidence of what was actually done to repair it.

In 1970, the person that I purchased it from acquired it from the Lynch family. He is a friend of the family and remembers the set always being in the downstairs basement rec room when he was a child.

It was used occasionally by him from 1970 to around 1980 and not turned on after that. It was moved from Michigan to Florida around 2002. I purchased it in 2005. My wife and I drove down to Florida, and brought it back to New Jersey.

It will be in the Living Room of our 1917 home on Christmas to display to the relatives.

Tim,
I agree with Pete, the focus control should not be at an extreme end of its range. Check the series resistor (8.2M), and the control itself. And try another focus rectifier, tube testers don't give a very reliable indication of actual circuit performance of HV diodes.

While you will never get the convergence perfect, you should be able to do better than shown in your picture. check the components in the dynamic convergence amp circuit (you probably already have), and keep tweaking it, you will get it better!

The HV performance you are observing is pretty much the way it worked the day it was made. You just have to resign yourself to watching the set in subdued lighting, and NOT be tempted to turn the brightness/contrast up as high as one would expect to.
Keep us posted!

didnt they used to say that you should watch TV in a darkened room anyway? I remember an episode of happy days where mr. cunningham told richie that...

Hi John:

Thanks for the info. It helps to know that that is not normal. I recall the 8.2M resistor was in spec but I do not know what it was. I'll reduce it to the low side of the spec and see what happens.

I have had 3 focus rectifiers in there with the same results. The current one is a NOS RCA. I am thinking that maybe faulty doorknob cap(s) is(are) contributing to the problem? I think I have something I can replace them with as a test. But the replacements I have are old as well.

I have now drunk the potion and adopted the creed of the HV challenged. :sigh:

didnt they used to say that you should watch TV in a darkened room anyway?

My mother always told me I would ruin my eyes if I watched TV in a dark room. :scratch2:

OH no, nevermind, i was wrong. kind of like burning in an image orthicon camera. just that bright TV "square" burned into you retinas.

I had it wrong, I think mr.cunningham was watching a scary movie and turned the lights up because he was scared, and give richie the excuse that "they say you should watch television in a brightened room"

Tim,
Check the series resistor (8.2M), and the control itself.Thanks John for correcting my mistake. It was written just before a 50-mile trip to the airport in a Michigan, lake-effect snowstorm. Okay, that's no excuse but it's the best I can conjure up for flipping the focus and convergence schematics in my head:screwy:

I understand the logic to that idea but does anybody know for sure?
Thanks


Tim, Thanks for the history! How did you come to find the set?

Please excuse me jumping into your thread. As a long time lurker, with little technical expertise, but an abiding interest in early color sets, I enjoy reading about your adventures with dirty tuners, fried coils and accidental zaps of HV.

I spent nearly 30 years in the film and television business and was transfering film to video in the mid-70's on an RCA film chain at Compact Video in Burbank that used a 21" roundie for a monitor.

We always viewed color sets in dim rooms. So dim, you needed small lamps to read and write notes. This was true on film chains, with flying spot scanners, when editing, and when I was ending my work life, when I did high def transfers of 35 mm lo con reversals and color correction of 2K digital film files to HD. CRT color sets (and I believe plasma also) are best seen in dim, diffuse light, almost like a movie theater. At least that is what I was taught, and my eyes told me.

And as far as I know, no one ever went blind watching those sets.

If this sounds preachy, please excuse me, but that was my experience.

If this sounds preachy, please excuse me, but that was my experience.No excusing necessary, or course, and welcome to the 'active' side of AudioKarma. Anything you might be able to share concerning the use of 1953 NTSC color would be appreciated. For example, is there anything today that can drive a '53-color-capable set to its full gamut capabilities?

Yeah, pal, welcome to our little Mad Monks of Ancien' TeeVee Society...

Regarding interlace effects in tube-pickup cameras: the lenses were never designed to reduce this effect. doing so would reduce the over-all impression of sharpness too much. The scanning spot size in the pickup tube, however, was made large enough that it would scan the whole target in one field, that is, the spot was wide enough to discharge the spaces between the lines as well as the lines themselves. If it happened that the spot was too sharp, you would get a fluttering brightness variation as slight variations in the location of the scan lines would lead to an area being insufficiently discharged on some fields and then the excess charge being read out on later fields. In CCD pickups, the moire problem is reduced by reading out rows of pixels in pairs, i.e, on field 1 rows 1&2 are combined, 3&4 are combined, etc., and on the field 2 lines 2&3 are combined, 4&5 are combined, etc. - so again, the whole device is discharged in one field, even though there is a 1-line offset between fields.

Regarding viewing in a dark room: there is a SMPTE standard somewhere, I believe, for monitor viewing conditions, and large broadcast organizations have standard control room illumination specs also. The typical spec is to have no direct light on the face of the CRT, and the picture surround illuminated to a dim neutral value (say 10% of picture highlights? - I don't recall the exact spec). The "no light on the faceplate" rule is less important with modern low-reflectance displays - some LCDs are so good that it is irrelevant since they still appear black even with very bright light falling on them. However, the rule of viewing with dim SURROUND still applies, since this is the condition under which the tonal rendition is judged at the studio.

Regarding high-def lenses, there definitely are such things. Lens designs involve such severe tradeoffs of various parameters that it is very difficult to maintain good image quality with the huge zoom range that is available in current video lenses. The tradeoffs are not only various types of distortion, but important practical things like size and weight. So, a lens that is good enough for standard def may be seen to be deficient under some conditions with a high def camera. There also has been a great change in designs for CCD cameras compared to tube cameras. In the high-end tube cameras with high end lenses, the lenses actually contained circuitry that reported the lens settings to the camera, which then adjusted the scanning to compensate for the lense distortions. Now that cameras use CCDs, that compensation is not possible (at least not without some very difficult real-time digital interpolation). Hence, extra care is needed in the design to maintain low distortion at all zoom and focus settings.

see! :P

I think what was writtten by TVnut confirms the point I attempted to make which is that I expect the technology to make special lenses was perfected long ago and the lenses used in the early high end tube cameras were actually of today's technical standards.
In other words: Like many things, It was good enough by the 60's.
I think there are more important things to tend to on this planet then new TV's that do the same basic thing they did in the 60's.

People today get into details that do more to kill our short time in life than any percieved good.

didnt they used to say that you should watch TV in a darkened room anyway? I remember an episode of happy days where mr. cunningham told richie that...

Of course this explains the wide variety of "TV lamps" that were popular in the late 40's and well into the 50's. These small lamps, usually a porcelain or highly glazed animal figure, graced the top of the family tv. This may have been the only illumination in the room other then the tv itself. The use of safety glass in front of the tube also acted as a reflection magnet, from other room light, on the viewing screen. E-bay always has lots of these lights up for bid, and a '54 CT-100 is a great candidate for one of these relics. Straying off the original topic here, I know.

-Steve D.

No excusing necessary, or course, and welcome to the 'active' side of AudioKarma. Anything you might be able to share concerning the use of 1953 NTSC color would be appreciated. For example, is there anything today that can drive a '53-color-capable set to its full gamut capabilities?

Oh-oh - time for a little more tutorial:

The signal specs for NTSC have never been changed, that is, the I,Q and Y signals have the same range they have had from the beginning. So, existing signals will drive a '53 color set to its full range. However, IF the camera has been matrixed for modern phosphors, it will drive the '53 set to full range on the wrong colors. Example 1: An NTSC-matrixed camera sees a yellowish green (the same as the modern phosphor) - it doesn't produce full G-Y drive,or full (negative) R-Y in the '53 receiver, since it knows the color should be reproduced with some NTSC red in it to make the yellowish-green. Example 2: An NTSC-matrixed camera sees an NTSC-green color - it produces a full strength G-Y and (negative) R-Y and (negative) B-Y, so that pure NTSC green is produced in the '53 receiver. Example 3: A camera matrixed for modern phosphors (essentially a HDTV or PAL camera) sees a yellowish green (equal to the modern phosphor). It produces full strength color difference signals in the '53 receiver, since it is expecting to produce pure yellowish green from the modern phosphor - but the '53 receiver is driven the same way, producing the (wrong) pure NTSC green.

Pete, you are just going to have to get yourself a TK41 camera (and the room full of equipment to support it!

me first

Pete, you are just going to have to get yourself a TK41 camera (and the room full of equipment to support it!Maybe Chuck Pharis will sell me what I need.:D

Could this quest be a near miss?: As in Wayne's example 3 above, the OTA transmitter is capable of transmitting it, but the camera source isn't '53 NTSC, so that doesn't quite fly. Ed's method uses a high-quality vintage recording of a program shot with TK-41's, but it's not going to be transmitted OTA, so the Radio Shack, or whatever, video modulator [DVD -> RF MODULATOR -> CT-100] is unlikely to match a broadcast transmitter spec-for-spec.

Also in question is the capability of a DVD (ostensibly the source of TK-41 based video) to reproduce the original vintage video accurately. I'm thinking of VHS tape. As popular as it was, it doesn't reproduce NTSC in all its glory. What about a DVD though? It's capable of greater resolution than the NTSC standard, so perhaps it can deliver true '53 NTSC color as well.

Hopefully, all the issues are minor and won't aggregate into visible distortion.