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#1
02-05-2014, 08:13 PM
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Cary,
Whatever you do, please hold off on any idea of shooting the CRT with a 'juvinater. It's very easy to wreck the tube, specially if you don't have prior experience using one. If the tube is actually weak (which hasn't yet been proven conclusively), a brightener is the much safer way to go, for a noobster. 
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#2
02-07-2014, 04:48 AM
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Don't worry about the rejuvenator. I'm not even close to seeing one in real life, let alone having one in my hands to fool around with. There's a few other things I'd like to try, involving adjustments and circuitry, first. I'm not even sure I know what I'm doing with that yet...after doing some reading I find I might have gone about adjusting the yoke and ion trap all wrong. And there's a couple of adjustments in the high voltage section that I have no clue about. One is a screw painted red, with a silver screw next to it. I'm going to have to read up some fine print in the Riders and SAMS to see if there's any mention of it.
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#3
02-06-2014, 02:43 AM
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it might be bending at the top because of the tape , tapes have that effect on some sets , the white lines being stationary sound to me like a weak crt , its because you have to push more brightness then required and its showing up .
agreed it wont hurt to try a brightener and if it looks much better you will have your answer , on rare occasions you can run a set with a brightener for lets say an hour , remove the brightener and it might work ok without it after that but that's rare there are series and parallel brighteners , I can't think at the moment but I think you want a parallel , someone correct me if I'm wrong.
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#4
02-06-2014, 12:52 PM
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If your heaters are wired in parallel you want a parallel brightener, if they are series go with series. Don't use one that is an 'isolation' type unless your CRT has a heater-cathode short.
Retrace lines can be an indicator of, but are NOT definitive proof of a bad CRT and can occur in a set with a perfect NOS CRT if the circuits are malfunctioning, poorly adjusted, or poorly designed. The blanking circuit is usually a resistor/capacitor network going from near the output of one or both deflection circuits to one of the video stages. It feeds back the retrace portion of the pulse to the video stages turning them off HARD on the retrace. If those parts have drifted in value or failed it can cause retrace issues. Some sets had the circuit, but it was insufficient or ineffective if the CRT emission changed slightly. If your set has an AGC control (when mis-adjusted it can cause retrace lines) I'd try adjusting it in conjunction with brightness and contrast to see if there is a good compromise that reduces retrace lines. CRT rejuvinators are a mixed bag. The newer/est ones tend to be gentle and some of them are nearly fool proof, but many of the older ones going up into at least the 60's use 'Atomic blast' (modern VK slang) rejuvination circuits that tend to destroy as many tubes as they help...Though dead tubes that the safer rejuvinators can't help sometimes will be fixed by an 'atomic blast' rejuvinators. Rejuved CRT's don't always last some need a mild rejuv every 5 years and it brings them back to like new, others come back to varying degrees and fall back or below what they were at within hours or days.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
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#5
02-07-2014, 04:37 AM
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I took another look at Phil's write up of his DuMont restoration, and saw a photo of the "scan lines", and that is exactly what I'm seeing. Information overload apparently caused brain-fade. I usually remember stuff like that visually.
I also saw how his set suffered from lower-than-normal voltage from the high voltage section, which contributed to a VERY dim CRT initially. His fix involved replacing a bad 270uuf mica cap marked C245 on the schematic. Looking at my order sheet from "JustRadios", I see I ordered a couple of these...and remembered they were just for this purpose. I'll try replacing it in the AM and see what happens. Can't hurt since I already have the cap here.
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#6
02-07-2014, 06:37 PM
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Wow!
I didn't think changing out ONE mica cap would cause such a problem. I had a stable, if slightly dim, picture before. Now I can't get the picture to stabilize for more than a few minutes at a time. Adjusting gets the picture looking great, and then for no apparent reason, I lose it and get..well..the photo will tell the story. So now I have a BRIGHTER bunch of hash. First picture, before the change of the cap. Second picture, after.
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#7
02-07-2014, 08:36 PM
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I'm using factory numbers for the R113 and I am confused as to what your are talking about. Did you change C-245 the 270 µµf mica capacitor that goes between pin 4 of the 6SN7 and pin F of the horizontal transformer Z-210? If so, C-245 will affect horizontal sync, but I don't see any way this capacitor could affect vertical retrace in your picture or the brightness (provided it did not change the width of the image.) Have you replaced the 6SN7 that changed the picture when thumped? This usually is the sign of a shorted tube. If it now is in the sync circuit, it could well be the cause of our problem. If C-245 is the part that you changed, you need to recheck all your changes for a wiring error, wrong value component or an over heated pin on the transformer while soldering, or a cold soldered joint. Once you get the set back to working, for either retrace or lack of brightness on a set without traditional sweep blanking, the first thing I would check is the DC restorer. My first check in the DC restoration circuit would be to measure the 1 meg resistor on cathode and check the voltages on that tube and also try a substitute 6AL5. Where your retrace only shows at the top of the screen, usually this is caused by a wave shape error on the vertical sweep spike, although I've seen a gassy CRT do this. (The spike is the part of the sweep where the beam moves back to the top and if it slows down near the top, it often will be visible.) Jas. Last edited by earlyfilm; 02-07-2014 at 08:42 PM. Reason: corrected sequence of checks
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#8
02-07-2014, 10:12 PM
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You may have a point about me expecting more from the CRT than it was designed to deliver. I don't have any point of reference to compare to since I never have ever seen this set working before. I'm probably expecting too much from 1950! However, that image of the picture is with the brightness and contrast almost all the way up. Towards the middle of adjustment, it would fade to black. And I will say that the photograph does make the picture appear slightly brighter than it is in real life. But I did take that photo this afternoon, with daylight in the room. According to Phil's write up of his RA 113, he experienced a dark picture because he wasn't getting the high voltage required. He states he was only getting about 4000 volts, when the tube was supposed to be getting around 12000, I may have misunderstood what he wrote, but he found the waveform associated with C-245 incorrect, which seemed to be associated with the voltage deficiency. I'm not real knowledgeable in this, so I was duplicating what he did. http://www.antiqueradio.org/DuMontRA-113Television.htm It did seem to work somewhat. I don't have any way at hand to check high voltage, but I do have some old electrical test gear out in the shed that I'm going to dig out tomorrow. I think on of the testers will test high voltage, but I don't remember how high. You hit the nail on the head about the C-245 mica affecting horizontal sync. I found that little "extra" adjustment on the chassis, right next to the 6BG6G tube. Once I made the adjustment and got the picture back, it did seem to be a bit brighter. But I could be seeing things, and it was getting dark outside by then. I don't have any spare 6SN7 tubes yet, nor 6AL5's. I plan on getting a stock together of extra tubes for the set, but haven't had time to to locate and order them all yet. I'll make sure to put 6AL5's on the list of "must haves" too. This sure is a learning experience! You will probably get a kick out of my next post!
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#9
02-08-2014, 08:07 AM
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If the image blooms (it suddenly gets bigger as it dims out) before it goes out, look something restricting the HV current to the picture tube. This is the normal symptom of sudden high voltage drop. The most usual suspects are the 1X2 tubes. And no, you cannot test one 1X2 by switching it with the other one as they work together to form a voltage doubler. * If he image does not bloom, and the image stays close to the same size, look for the problem in either the video output, DC restorer, brightness control or picture tube circuit or the CRT itself. (The latter is not too likely.) * If you had a scope, you could confirm that the waveforms and signal level going into the grid of the horizontal output are correct. You really need a known accurate HV meter before you go messing with the HV adjustments.
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#10
02-07-2014, 10:13 PM
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I agree that first picture is actually really good for an old set in what looks like a very well lit room. Any chance you kept the old mica cap you replaced? If so I'd try putting things back to original.
[edit] oops, I see you posted the cure for your problem while I was typing my message. BTW you've done an excellent job of bringing this set back to life. Not an easy task for a first time TV restoration. Last edited by Kevin Kuehn; 02-07-2014 at 10:18 PM.
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#11
02-07-2014, 10:17 PM
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Here's a good one!
Take a look at the photo and see if you can figure out what's wrong. I've done that TWICE today! ARGGGGGHHHHHHH! Gonna go take it apart again and retrieve the adjuster...again! I did find out there's resistors in there! Another learning experience!
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#12
02-08-2014, 09:56 AM
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Quote:
  That looks like a video IF can. It has nothing to do with horz sync. Hope you can get the slug back to where it was. Hope you haven't turned any of the others.
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#13
02-08-2014, 02:42 PM
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Let me chime in and agree that your picture looks pretty darned good. 60-year old TVs are not like modern plasmas. They were watched in subdued light, not bright sunlit rooms.
It's possible that you are very nearly done. As old_coot88 recommends, I'd be very cautious about turning any adjusters unless you have identified them in the manual and you have a clear plan in mind. The video IF adjustments are critical and you should not touch them unless you have specialized equipment and the experience to use it. Part of restoring a vintage TV is learning how a TV from those days actually works (for better or worse). You might want to sit down in the evening and watch the TV for a while -- give it a little shakedown cruise. How is the stability? Are you constantly jumping up to adjust something, or can you basically sit back and enjoy the show? What's the audio like? How does the TV audio compare to audio in FM mode? (The audio is usually louder in FM radio mode on this particular TV, but the quality should be about the same.) Take some time to get used to the continuous tuner, so you know when you have found the spot where you get the best picture and the best audio. If the best-audio spot is far away from the best-picture spot, then perhaps it would help to tweak the audio adjustments. And so on . . . . Regards, Phil Nelson Phil's Old Radios http://antiqueradio.org/index.html
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#14
02-11-2014, 09:26 AM
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I do agree that I would have preferred to not have to adjust any of the IF cans. But that ship sailed decades ago. When I brought home the set from my grandparents house decades ago, the adjusters had already been tweaked, possibly many times. I found some were turned all the way out, some turned all the way in (hence the one the "fell" into the can a couple of times. It apparently no longer has the "stop" the others do). As a result, the initial picture was not as good as it is now. It was "blocky", and had a lot of "ghosts". My grandfather was a big "do-it-yourselfer", and my mother confirmed a few nights ago on the phone that he tried to fix it himself back in the 1960's, but I doubt he ever had the SAMS or Rogers references to start with. I spent a lot of time with grandfather, and worked with him in the construction biz back in the late 70's through mid 80's. I credit my grandfather for my "gumption" to tackle new tasks. When I was young, faced with some seemingly insurmountable task, and would ask "Can we really do it?", he would say "Somebody built it." or something appropriate, and we would dig in.
I would love to have the equipment to "set it and forget it". I'm hoping to have access to an oscilloscope and signal generator eventually, perhaps borrow them if I can find someone who has them, or even if it means buying them myself. Then I can follow the alignment directions in SAMS and be done with it. In the meantime, in order to get the picture I have, I've had to spend hours looking for the "sweet spots" and learning how the IF adjusters affect picture and interact with each other. Admittedly not the best way, but right now, it's the only way I've got. I also followed the "AGC" adjustment and horizontal sweep adjustments in the SAMS (sans the equipment for the horizontal sweep, thus relying upon my best judgment of picture, of course) and it's all been good. In fact, that alone brightened the picture immensely. It will be interesting to see, eventually, how close I got.) One of my frustrations has been that the test pattern DVD made with files downloaded from the internet works great in the computer's DVD player, but won't play in any of the actual DVD players I've tried it in, so I'm having to make adjustments with static images from shows. We watched a few hours of "Get Smart" last night and I did notice some bright white "blips" along the "scan lines" that faded away with warm up. But after a couple hours, during an episode that had much brighter backgrounds than others, they reappeared. Looks like I've got some more tweaking to do. Also, it seems the "scan lines" appear, quite faintly, against a dark background even when the brightness is turned down quite a bit. Interestingly, in the copy of the original "SAMS" folder I have, on the schematic someone had used a pencil to circle "C2" 50uf cap, and wrote "vert jitter retrace lines". I know this is a long shot, but are there any "old time" do-it-yourself" processes for video alignment for folks who didn't have scopes and signal generators and such? I'm kind of having to make this up as a go along, but maybe I'm "re-inventing" the wheel. And check out that brand-spanking-new eye tube! It's action seems correct, in that it does move maybe a quarter inch up and down when it's slightly "off signal". However, when it's not on a channel at all, it lines up pretty good as well. As I get to a a video signal, it moves either up or down, and then lines up again, apparently when I reach "center" of the best signal. Is that normal? I've read where the action of this particular eye tube is not very "intuitive"..especially considering the left bar's BOTTOM edge is the one that is supposed to move up and down...and I have to agree it's pretty funky.
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#15
02-11-2014, 10:29 AM
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Back in the day there was a shop that had a proficiency test for new hires. The boss would take a set and deliberately throw the vid IFs off. The applicant was expected to re-align it using the full suite of equipment (sweep genny, scope etc.) The fact that you've got a watchable picture on the set is nothing short of a miracle and testament to your Granddad's indomitable spirit and admonition to "dig in and do it." It's virtually fulfillment the Sea Bees' motto: The difficult we do immediately The impossible takes a little longer. My hat's off to you Sir. I would never have even attempted it. The usual symptoms of misalignment are loss of fine detail in the pic, smearing-out and ringing of the vid signal. The best advice at this point would be to not try to "improve" upon what you've got.
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