Two birds with the same stone on this one? :beatnik:

http://www.ebay.com/itm/NOS-Zenith-S...p2054897.l4275


Zenith branded for true authenticity, and you no longer need to worry about heater juice. Sounds like a good deal to me. :yes:



(No affiliation with seller.)

Have you ever tried a solid state replacement? My only experience is watching a video by one of our members on YouTube where he tries one and the set absolutely would not operate correctly with that type rectifier in it. He went back to the vacuum tube and all was fine.

I just suspect that the arching that went on in more than one place with my old socket got the best of the tube. Months ago before any of the socket issues developed I put and International Servicemaster in the set and it only lasted a few minutes. The one that I just pulled out and tested bad was used before that and up until the socket issue of late. Hopefully another decent quality tube will take care of things.

For the price including free shipping, I would definitely give it a try if the set was on my workbench. The advantages of the solid-state replacements are: reduced loading on the horizontal output tube and flyback, as there's no filament to heat up, and you can drastically simplify the connections to the socket. Literally all you need is the connection to the anode lead/HV regulator tube coming out the bottom. I'd unhook the filament loop, insulate the ends, and tuck them away in case they're needed in the future.


The voltage withstanding and current handling capability of the S-3AT2 replacement exceeds the specs for the normal 3AT2 (A/B) series.

Send me a PM with your email address and I can send you the full resolution pictures of the schematics. Upload to this site compresses the heck out of them and makes them look really fuzzy. A quick look at http://www.vacuumtubes.net/Prices%200A1%20to%203Z4.htm
shows they sell 3AT2s for $3.00. Other places are probably similar prices. I usually get two of each tube I order to have a spare and in case one is not so good.

Actually, a bad 3AT2 matches the Goodman description of the burnt resistor problem.

Dave

The only time, I used a SS replacement, was when the filiment loop was punctured through and arcing. I cut it short or tried to remove it completely.
Never had any problems. Usually on an RCA or one of the clones.

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.

IIRC, the original 3AT2's were made by GE. The Zenith replacements were made by Sylvania.
You should've mentioned the 3AT2. I could've included a good used one or two. :thmbsp:

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.

Ken-Rad was one of the oldest tube suppliers out there. Their tube stood up as well or better, than a lot of the other brands. :thmbsp:

For the sake of this thread's information being accurate I must correct what is quoted above. My set's chassis is indeed a 25LC30 and the model is 5111. I don't even know where I came up with 25MC30 being what mine is. I am guessing that the L & M identifiers must have to do with production year. Mine should be the 1964 and the MCs should be 1965 and the last of that style plain metal cabinet round crt TV production.

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....:thmbsp:

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!

Have you tested all the tubes in the color section? If not I recommend doing so. My set had no color, then I tested the tubes in the color section, and found most were testing bad to very weak. After replacing all the color tubes that did not test decently the color section came back STRONG.

Are you familiar with the color killer adjustment?
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.

Great hear you got the HV problem solved and the set operating again. Good tubes and caps can make for big improvements.

Dave

I did test the tubes a long time ago on my Hickok 6000A. I think I will do it again on my new B & K Precision 747. Oddly, I get color when the set wants to and when I do it is beautiful. It always seems to happen when I use a DVD/VCR combo and run the line E up a bit. Coincidence perhaps.

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.

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.

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.

The color killer has nothing to do with convergence. If the set has color fringing from imperfect convergence, the color killer will not make that go away even if cranked to the B/W only end. Use a test pattern to get the static (center) convergence perfect, then adjust the killer so that the perfectly converged portion of the screen (center) has no confetti (ie color snow), and ignore any fringing from mis-convergence elsewhere on the screen.

Sorry, I need to watch my terminology a bit better and give more precise descriptions. I will edit my post a bit. I did realize that the fringing would be there either way as far as the color killer went. When I mentioned everything (at times) being as it "should be" I meant when the color actually has worked and worked well. The fringing I mention is due to myself or someone turning the convergence clover several degrees.

Shouldn't I do a purity setup before any convergence?

If the purity is good one can often adjust the convergence without having to mess with it.

You mean to say, they don't know Thevenin and Norton's theorem either? :D
I'd have to get back to the books! It's been years. :sigh:

No they don't. Ohm's law would be the only thing that a modern JR college curriculum would include and perhaps Kirchoff's Law; and that would be very limited. I don't mean to put the younger techs down for what they were never taught. I just think that it's a shame that what was once a respectable discipline that was pretty darned involved and anchored in the roots of the science of electricity/electronics has like so many things been dumbed down so, yet the students attain the same credential as students of old who I feel had to work harder to get what they got.

I have been told that my mindset on this suggests that I or anyone else should attend a university. I say that's wrong because you are not going to perhaps get through a high school trades course and then get a couple of years of college under your belt to find yourself beginning the theories and the math to prove them which is the foundation for all of what we do when completing your Bachelor degree which at that point would be electrical engineering. I guess there are better and worse JR college programs and a lot of what I remember was a bit of a joke. And that's back when it was a lot harder than today.

I remember an exam question on the definition of voltage. The correct written answer was "a force." Sure, it's a force. So was a big part of Star Wars! Just an example. I am told now that they have almost completely converted the focus to what is known a Mechatronics. Basically automation, so some factory can get you to be the grease monkey and the electronics tech. The I.T. guy gets an office! So the college tossed a truckload of oscilloscopes, function generators, Variacs and other great tools in the dumpster one day. You couldn't even buy them as they were government property to be destroyed. I won't bother going into grading most tests based on the lowest grade so basically nobody flunks out. Money!!!

Update pics for 65 zenith
 

OK folks, as promised; here is where I stand. I didn't want to post pics until I had a decent color picture. I think I found and tested 10 6GH8 tubes before I found one even marginal one one of the two tests for that tube. The rest were LOW emissions. I have heard that the 6GH8s were lousy tubes and my B & K Dynajet 747B sure proves that. I notice that there are some common subs like 6U8 and 6EA8 that may work, but I had none on hand. Anyone every tried any other subs?

But as for the whole HV rectifier project; it looks like a wrap. Very stable and still using a slightly reduced line voltage I can maintain less than 200mA at the horizontal output's cathode. The fly seems to be running cooler than it was when I had the old socket and corona hiss. I absolutely love that silence and a cool fly.

I am really surprised at the generally good color picture with really no alignment. Not proper anyway. I did set the service switch and touch up the guns to get as good a white line as I could, but there really wasn't much to do there. Next comes the use of the same age RCA dot bar generator as up close there are obvious alignment issues. I think it will be stunning when I work those out.

Thanks again everyone for the help on this!

Tube

Lookin' good!:thmbsp:

Good job!:banana:

Heck, I learnt sumpthin' too.. the resistance wire used for the 3AT2 filament.:o

Nice work.:thmbsp:

Thanks to Electrronic M, Zenith6S321 & Old_coot88 for the kind words. I tell ya; one thing about messing with old TVs (especially color) is that there is always a new mystery or maybe some adjustments around the corner. The lovely pic of Ray Charles was actually taken with the set on it's side for service next to (of all things) my Frigidaire.

So, I'm finally ready to set her down for normal viewing and powered her up; color gone. And my black and white wasn't so black and white anymore. The intermittent color I deeply feel is that darned 6GH8 Chroma Reference Oscillator that I mentioned in an earlier post. What is up with these 6GH8s?!?!? Anyway, I think the rest of my impurity is a magnetized C.R.T. or simple purity adjustment as I had moved the rings some while it was on it's side.

I may be able to dig a couple of healthy 6GH8s out of my tube stock for you if you need them.

When I first started on my 29JC20, the color would work but then quickly fade away as it warmed up. Is that what you see, or is there no color when its powered up cold?

Make sure you test any used with something like a B&K 747. I have so many tubes from Zeniths, I sent Greg a variety of tubes for his set that tested great on my emission tester and they failed on his.:no: Since I now have three of these Zeniths, Im really paying attention so I can maybe solve some of these riddles for the benefit of all.

Anything octal/loctal or newer I test on a B&K 606 (it works good so it is all I use where applicable).

That would be cool; really cool. Even one good one would be nice. Also, as it was brought up, I use a B & K Dynajet 747B these days for the most part or sometimes a Hickok 6000A, so I have little fear of mis-testing. I have seen it on a plain emissions tester that I have by Accurate Instrument Co. Almost all tubes test good. Weird! :scratch2:

Also, I found a bad 6KT8 last night and sort of ended up in the same situation with a bunch of bad ones. Several were the ones that Dave sent me and a few were my own. I have one more box to check for others, but may need one of those if plentiful. Let me know what you find Electronic M. Thanks!

No, I don't see the former, but I do see the later. My set often (more than not) starts off in pure black and white with the exception of impurities now that my Frigidaire magnetized my tube or possibly other adjustments like purity rings need to be adjusted. Anyway, no color until after quite a bit of warm up. Maybe 20 minutes or so. Once it's there, then it's there to stay normally till I shut her down.

As previously mentioned, I am working with more than one marginal at best tube in the color circuits. That may be the whole thing. I hope so because I want to get this thing stabilized and get my same vintage RCA color dot bar generator hooked up and do her up right! :thmbsp:

(Edited cause I forgot this is not a 29JC20!)

It still could be an effect of the Zenith automatic control control/color killer that caused my color fading issue. One way to see if that's it is to disable the color killer. If your color comes back then its not the 3.58 MHz oscillator that is causing the problem.
Dave

That sounds like a good idea. I will keep it in mind. Tonight I powered it up and it almost seemed like color wasn't going to come in. I started tweaking the killer and the tint and the color just came in. I REALLY need to get into some purity and static convergence when I get stronger tubes in there. I tested my 6KT8s on my Hickok and the Accurate Instruments for comparison. All good on the Accurate and all weak on the Pentode test with two having marginal triode tests. I used the stronger one of course. I think that the color takes so long to come in due to the marginal emission and a usually reduced line voltage causing slower. I have noticed that I can bump up the line voltage and shortly thereafter the color will come in; then I can back off to ensure the 200mA horizontal output cathode current and the color will remain.

Question: When I am setting up my convergence clover, is the black line on the crt's gun an index as to where the plastic edge of the clover should go to have it directly over the beam converging pole pieces? Some of this has been moved and I want to have it dead on so I can slide the yoke back and work my purity rings for a red center; then move the yoke back till I achieve the best red screen possible. This of course with the other two guns extinguished.

Ignore the test point from my previous post. I was thinking this was a 29JC20, so your test point is probably labeled differently.

Here are pictures from Goodman of the CRT pole piece positioning for roundies.

Wow, small world. I have those two shots in a (one of many) book I have called "Color TV Servicing Made Easy" by Wayne Lemons and Carl Babcoke. It's a Sams publication and is wonderful. Guess that makes me look pretty bad, but there is a method behind my madness.

The book simply says to position the clover "directly over the convergence pole pieces." It even shows what that is as seen in the electron gun breakdown. My question was derived from the fact that the area is blacked out where you don't see the pole pieces. The blackened area clearly ends about where the clover should be. I thought perhaps the black line could be a reference point placed as the pole pieces can't be seen. I'm not sure of the distance toward the yoke that this black area goes.

I am trying not to move things a lot as I have pretty decent color. I have moved the clover enough to see that it's placement forward or back even a small distance makes a big difference in alignment. I guess I may as well just slide everything back and see if I can view the pole pieces. After all, I could be having to put in a new crt and be removing all of this stuff anyway. I just thought that if this were an indexing mark it would be nice and useful too.

I went ahead and just placed the plastic edge of the clover right at the metal disc for the pole pieces which is all you can see. I loosened the yoke and pulled it back and turned all but the red screen down and tried to move the rings to get a red splotch somewhere near center. Unfortunately, I can't get a red splotch at all as I have seen in some good YouTube videos by a member of VK. It seems I can conjure up all kinds of combinations of colors and even almost totally blue, but no red center.

So I just got it as red as I could and slid the yoke back. Definitely more to do there. I had to just further manipulate the rings at that point to get a somewhat uniform red screen. I really think that I need to get a degauss-er for one thing. I wonder if some magnetization could keep me from achieving the red center on that procedure....

Manually degauss, and if that fails move the yoke farther back (even if you temporarily have to slide the convergence yoke back a bit to make it work).

OK, that sounds reasonable. I will try moving the yoke back as you said and see what happens. I don't have a degaussing coil, so I may as well try whatever I can. Those weak tubes I feel still have me waiting a long time for color, but at least I know that it will usually come in.

I have an RCA WR-64A color dot bar generator that I hooked up just for the heck of it and the thing worked for a few minutes and then my sync started going whacky. So I put it on my daily watcher and the same thing happened, which to me was good as it told me that it wasn't some issue with my old Zenith. I smacked it on the side (generator) and the sync problem went away. SO, I probably need to clean up some tube pins and sockets and I will have that rather handy unit ready.

Never a dull moment in this saga! BTW, I know they make DVDs now for alignment. I'm sort of a fan of vintage test/setup equipment and it was a gift, so I may as well put it to use.