#46
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Well, I sort of opt for originality when possible, so I called that supplier that Zenith6S321 posted a link for and have a couple of those and one or two other radio tubes I needed on the way. I inquired about what brands were available and was blown away as the guy named almost anything one would desire or not (International Serivicemaster). They actually had Zenith and put me down as preferring that. As a second option I told them Sylvania. I don't think I can go wrong with either of those.
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#47
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You should've mentioned the 3AT2. I could've included a good used one or two. |
#48
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All is well that ends well with that. They did send me 2 Zeniths, so I will have a couple of good NOS tubes. I haven't had time to try one in my set yet. A third and different tube for a 40s radio was a Ken-Rad. I've had some, but I can't remember how they held out. Shouldn't be a problem. I sent you a PM.
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#49
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#50
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Thinking I had the wrong schematic, I ended up finding a .pdf Sam's folder on the 25MC30 and was happy. Looking over the horizontal output and HV sections of the schematic I noticed that the 6JS6 horizontal output tube was used. I knew that my set employed the 6HF5 sweep tube. That led me to look at all the models covered for that year 1965 on the first page. I saw that the models were all different and mine 5111 was not there. I think instead there is a 5211 which is probably that year's equivalent. From there I opened my original file for the 25LC30 and saw my model and the right 6HF5 sweep circuit In a way I wish that my mistake was correct as I have heard that the 6JS6 H Output tube was a better tube by design (plus I have a few in my useless compactron box). I don't think that they are subs for one another, so I won't even worry about that. The 6HF5 seems to do as well as any. I'm not sure how many other changes that there were in that one year. Most everything I glanced at looked the same. I notice Zenith regularly made small changes such as one or two tubes from year to year. That's the world of engineering for better or worse. I wonder how much better the 6JS6 really is just out of curiosity. Anyway, I think the confusion on my part started with all the talk about the HV rectifier pin #s shown on my LC schematic. They appear to be wrong as pins 1 and 12 are shown to apparently be the heater terminals. Well, they are and they aren't, but you have to have the tube data to see what is going on internally with the 3AT2. Many pins are duplicate or NC. The MC schematic shows the same thing and it thew me off because I expected my set to be wired like the schematic as I would think a factory would adhere to; evidently not so. If anyone here needs a good copy of the 25MC30, I now have it and would be glad to share it with anyone. Just let me know....
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
Audiokarma |
#51
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OK, it's official! My HV is back. The surgery was a success thank goodness. I was a bit nervous of what new surprises may arise, but the only changes were definitely positive. Good, stable HV with no corona hissing and/or related screen anomalies.
I did use Electronic M's advice and paralleled a .47mfd cap across my meter leads measuring cathode current at the horizontal output tube. The readings were the same and unfortunately still a bit higher than I want, or Zenith wanted for that matter. The spec is 200mA and at line potential upward of 120VAC I get about 220mA. So I still run the set on my Select a Volt at about 110VAC and can maintain 200mA. Once an older tech said that they used to dip all the Zeniths at 210mA as a rule, but I feel that I should be able to achieve the spec. Now I do believe that the fly is now running much cooler for whatever reason. VERY happy there! I probably just need to change out the HO coupling cap to get the 200mA. That should be next because for whatever reason I have to throw a bit more line voltage at the set before the color will come in. Once it comes in I can back it down. The color problem has been with the set since I brought it home. Actually, there was no color for a long time and I changed out the 6GH8 one day and had a DVD player hooked up and wa la. Great color! For now though I'm just glad to have a playable set again. Many, many thanks to all for the help on this!
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" Last edited by Tubejunke; 03-03-2015 at 11:41 PM. Reason: mA |
#52
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__________________
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 |
#53
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To set it, you first turn the color control on full, and go to a snowy screen. There should be color speckling in the snow. If not, turn the color killer to the threshold point where color first appears in the snow, then back just a hair. That's the correct setting. Of course this is assuming the tubes are all good. |
#54
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Great hear you got the HV problem solved and the set operating again. Good tubes and caps can make for big improvements.
Dave |
#55
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Old_coot88 mentioned the color killer adjustment. I am guite familiar with that adjustment. Worked with it last night and got the snow and color fringing. I backed off till that went away, and then a little more as some fringing was still there. The idea which follows common procedure is to shoot for the perfect black and white picture which I can achieve pretty much. Once I get the color actually working regularly I will go through the whole purity and convergence procedures using my vintage RCA dot bar generator.
__________________
"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
Audiokarma |
#56
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While chasing the intermittent-color problem, leave the color killer adjustment full 'on', all the way to the stop, while troubleshooting.
In fact, you could leave it full 'on' these days, since everything is broadcast in color. Whereas in the old days when some broadcasting was still in B&W, the color killer circuit served to turn off the chroma to prevent color artifacts in the BW image. It works by sensing the presence or absence of the burst signal. Today, that function is moot unless something is being transmitted in actual (burstless) BW. |
#57
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So if I leave it (killer) on and when everything is as it should be, the snow will more or less go away. I had assumed that not to be the case and setting it too high would be about like setting AGC too high. I fully admit more or less being fairly new to troubleshooting vintage color television beyond that of normal static convergence and other setup procedures.
This is the only vintage color set in my ever smaller TV collection (due to space and sanity). My primary interests have always been in earlier black and white sets and radios. I have owned a number of round tube color sets back when they were available very cheap and made great daily use sets. So bringing one back from decades of dormancy is new to me. Thank God for the incredible pool of great people and knowledge here at VK to pass along what I as an electronics professional consider a lost art in the field that will vanish if not somehow kept alive. These days there are 'techs' who can barely read a meter; and I mean DIGITAL! They could care less about Ohm's Law, Kirchoff's Law,etc. To avoid a rant I will end this now as I must or that is what it will become.
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" Last edited by Tubejunke; 03-05-2015 at 08:49 PM. |
#58
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__________________
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 |
#59
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Shouldn't I do a purity setup before any convergence?
__________________
"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#60
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If the purity is good one can often adjust the convergence without having to mess with it.
__________________
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 |
Audiokarma |
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