View Full Version : Zenith 14DC16 Colour question/problem


maxhifi
12-20-2010, 01:42 AM
Hi All, new forum member here.

I have a Zenith 14DC16 portable hybrid TV set with single button space commander remote control. Have had it since 1994, when I picked it up for free. I have used it fairly sparingly over that time, and the only repair it has required, has been a replacement of both tubes in the VHF tuner.

I have the sams package for the set, and basic knowledge about how TVs work. Audio/radio have been hobbies of mine for years, but I have only done minor repair work on TVs.

In general the set is in excellent working order - the picture is sharp and free of noise, and the picture geometry is more than decent for such an old TV. The picture is bright, and when the image is a solid colour, it is consistent over the entire screen area.

Question is as follows... when watching certain shows, especially The Simpsons, it's extremely hard to get the tint to stay the same over the course of a show. In one scene, they look yellow, then the next a bit green, and in another a bit orange. In all cases I can adjust it to the right colour using the tint control, but then later on it will be different. Not all programs seem to show this effect, but when it is happening it is really annoying, and detracts from the otherwise perfect operation of the set.

I am targeting the 3EJ7 burst amplifier, and the 9MN8 G-Y, R-Y, B-Y amplifier as possible culprits. If either of these tubes are weak, or operating in some non-linear region, I can see how this would upset the colour. I have no tubes to use as substitutes, so thought I'd see if I could get a second opinion before I start ordring parts. There appears to be no electrolytic capacitors in the colour circuitry, and I am really at a loss as to what else it could be.

Any input from someone experienced with TVs of this era would be greatly appreciated.

ctc17
12-20-2010, 01:58 AM
Does that set have the quad detector diode tube in the color circuit? Also GH8s and KT8s cause issues like this. The bright solid colors in the simpsons really test the old color sets. Their yellowish color seems to be one of the hardest colors and results in red bleed on most of the old sets I see.

maxhifi
12-20-2010, 02:06 AM
Thank you for the quick reply!

So it might be something I just need to live with.

Colour section is hybrid, as follows

3EJ7 pentode Burst amp --> transistor amplifier ---> IC Demodulator ---> 9MN8 tripple triode voltage amp --> RGB grids of picture tube.

And add a number of probably germanium diodes to above

old_tv_nut
12-20-2010, 09:07 AM
Just guessing wildly, but:

Could it be the burst gating pulse is too wide and the color sync is picking up the left edge of the video? If you record and play back some Simpsons, you could try seeing if the variation occurs according to the color at the left edge of the picture.
If this set has a horizontal hold control, try turning it slightly to see if there is a hue variation.

ctc17
12-20-2010, 12:03 PM
If you want to try a 3EJ7 I can send you one.

Chroma alignment is something I want to work on. I have a great magazine article going through the alignment of a brand new Zenith and how much better it can be made.

I have 2 identical rca ctc35 chassis and one displays the simpsons perfect and the other has the red bleed. Thats using the same crt, yoke, convergence etc...so I know its the chassis. I tried switching the tubes between the two chassis and that didnt fix it. Its an alignment or cap issue somewhere.

maxhifi
12-20-2010, 11:07 PM
old_tv_nut:

Thank you for the suggestion!
I am using the TV with a digital cable box - it's strange, the horizontal hold control has almost no effect on anything. When I first got the TV, and was receiving over the air signals, the horizontal hold control was fairly touchy. So far The Simpsons hasn't been on, so I haven't had an opportunity to see what it does with colour. Next time it comes on, I am going to give that idea a try.

ctc17:

Your website is very interesting! I clicked on the link hoping to see what a ctc35 looks like and ended up spending 45 minutes looking at photos of tvs and other stuff. Drove through Death Valley for the first time myself this summer. Anyhow, would appreciate the 3EJ7. Last night I dug through hundreds of tubes, without any success finding one! I think it's at least worth a shot. Another thing about this TV, is my TV-7 tube tester is incapable of testing *any* of the tubes in the set! That's usually my first step in repairing anything with tubes in it.

ctc17
12-20-2010, 11:18 PM
Does your tube tester show a 6ej7? Use the settings for that and reduce the filament voltage to 3.

radiotvnut
12-20-2010, 11:21 PM
If you want to test later TV tubes, get either a Sencore "mighty mite" or one of the many B&K tube testers in the 600 or 700 series. These will test the later TV tubes, as well as older octal, loktal, and miniature radio and amplifier tubes. Also, these testers have a "grid emission" test; which, is very important for testing TV tubes. These testers were made right up to the end of tube TV production and between one of these and your TV-7, you should be able to test most any tube used in consumer electronics.

maxhifi
12-20-2010, 11:41 PM
ctc17:

Why didn't I think of that! Yes, the tester does list 6EJ7. Minimum good reading is 39 -- my tube reads 10!

radiotvnut:

Passed up on one of those B&K testers about 15 years ago and regretted it... this Zenith is my only tube TV, so haven't really had a reason to seek one out, but will keep my eyes open.

ctc17
12-21-2010, 12:16 AM
Ill try and dig one out in the morning. Dont get to excited, good chance it wont make any difference.

maxhifi
12-21-2010, 11:56 AM
ctc17:
It's worth a shot... Not expecting miracles. I thought the TV was worn out before I replaced the 2HA5 in the tuner. Now am adressing the less significant issues.

ctc17
12-21-2010, 02:10 PM
well bad news...I just pulled out the 4 I have and all of them test bad. 20-40%, I know its not the tester because I tried a new 6EJ and it checks 75%.

Grab one off ebay, they are only a few dollars, you can get 5 new ones for $10 so its not a rare tube at all.

maxhifi
12-21-2010, 02:53 PM
hey thanks for trying!
I think i will pick up a full set of tubes for the set on ebay, minus the horizontal output tube. It looks like most of them are pretty cheap and easy to find.

bgadow
12-22-2010, 10:12 PM
For what it's worth, I'm practically up to my ears in NOS TV tubes, if you (or anyone) is ever looking for something. Just send a PM with what you need and I'll see what I can put together.

maxhifi
12-23-2010, 02:57 PM
Thank you for the offer! I wish I had read that yesterday, I just placed an order for a full set of tubes for my TV, minus the horizontal output ($$$)

I have another question about this TV. What is the "peak pix" control supposed to be adjusting? On my TV, when you turn it down, the TV gets blurry, and the picture is best at the opposite extreme.

ctc17
12-23-2010, 03:46 PM
Its just that video peaking. Its like sharping pictures on the computer. I always leave them all the way up.

Does it use a xLF6 for the output tube?

maxhifi
12-23-2010, 04:16 PM
it has the option of 20LF6 OR 26LX6

Currently the set has a 26LX6, with red printing on it, marked Zenith Service, with a 1978 date code. It appears as though the horizontal output, damper, and vertical output were changed when the set was around 5 years old. The set has no symptoms of a bad horizontal output, so I will hold off until either it needs it or I hav e reason to believe it will improve performance

maxhifi
01-01-2011, 05:42 PM
Update on this set:

Have been brushing myself up on TV theory, and discovered some peculiarities about this TV. For one thing, it has RGB screen controls, but not drive controls. It seems to me that this is a design compromise, which makes it difficult to compensate for uneven aging of the CRT cathodes. Specifically, when the screen controls are set for proper white balance, the tint control has to be adjusted fairly far off centre towards red, in order to get accurate skin tones. Is this really a compromised design, or is there another way to go about setup?

Remembered I had another tube tester packed away. It is an EICO model 667, and once I found a comprehensive setting chart online, I was able to test all of the tubes in the TV.

Weak tubes include the final video amplifier, and also the 10Z10, as well as the colour burst oscillator. The only tube which tests in the "red" zone of the tube tester is the aforementioned colour burst oscillator. Luckily the horizontal output tests well into the green zone, at 120%

Out of curiosity I tested the old tuner tubes, 2HA5 and 4GJ7, and both tested in the "yellow" zone of the tube tester. In the set however, they completely ruin performance, the picture becomes overwhelmed with noise and snow. It makes me wonder what effect new tubes will have in other positions which are currently reading weak good, or marginal.

The set is displaying a few symptoms which seem to indicate a weak CRT, according to what I have read. Will reserve judgment until all small tubes are good, but symptoms are as follows:

1. Green appears a bit weaker than other colours, grass is always a bit browner than on other TVs. Nothing awful, but all the same apparent

2. When contrast control is anything above mid level, text on the screen has a bit of a shadow, “blooming” type appearance. It is still legible, but there is a definite loss of sharpness. This effect is worst with text on a dark background, such as movie credits or TV guide, and does not seem to affect normal video.

ctc17
01-02-2011, 05:20 AM
I havent figured that brown grass thing out yet. It seems to be one of the more common chroma issues. When you use a true ntsc color generator the yellow and green are all screwed up. I have 3 identical zenith consoles and one of them does it along with several others so I know its not the chassis design.
Its on the list of issues to figure out but it could be several months. My first step was going to be to sweep the bandpass and see what it looks like. The tint being off center could be a weak osc tube, cap or alignment issue. Most of the sets we deal with seem to have the tint all the way to one end. If your having the same green issue I am you will never get it right.

The Z10s always seem weak. The only difference you will notice is louder sound and maybe less buzz if you replace that one.

maxhifi
01-02-2011, 02:29 PM
Of the three chromacolor consoles, have you ruled out that it could be a problem with the CRT?

I am inclined to think in my case it is not, in my case, because the RGB screen controls are in the middle of their rotation in order to get good white balance. Nothing is pegged. I do not have a CRT tester though, so can't be sure.

Once my set of new tubes arrive, I am going to put some more effort into this. I think in the mean time I need to do more reading about how NTSC colour works.

ctc17
01-02-2011, 03:13 PM
Yes, its defiantly the chassis. I exchanged the chassis of two of them and the brown grass issue followed the chassis.

maxhifi
01-17-2011, 06:58 PM
Tubes for the set showed up last week. New colour burst oscillator seems to have cured problem. Simpsons look great now, tint control is a bit more into the red than I would like to see, but colour is stable and minimal red bleed. CTC17 has a great video about how to dial this out, and at this time I don't have the equipment or experience to do a colour bandpass alignment, but I feel as though I understand the issue a lot better than when I started into this!

Right now am in the process of acquiring an RCA 8PT, and will cut my teeth aligning that before I try it with a colour set. Luckily the Zenith has solid state IF amplifiers, so I didn't throw those out of whack by changing the tubes!

Set has a new problem. Everything is fine with brightness at normal, but when you crank it all the way up, the picture gets larger, and less bright. Why would brightness affect vertical size? Don't remember it doing this before I changed the tubes.

In general though it's back in top shape, have been watching it every day again.

compucat
01-17-2011, 07:53 PM
Set has a new problem. Everything is fine with brightness at normal, but when you crank it all the way up, the picture gets larger, and less bright. Why would brightness affect vertical size? Don't remember it doing this before I changed the tubes.

In general though it's back in top shape, have been watching it every day again.

The problem you are describing is called blooming and is usually caused by a weak high voltage rectifier tube. That tube is often located inside the metal high voltage cage with the flyback transformer. I have seen these tubes get so weak that when the brightness is turned up the picture disappears completely and the screen goes dark. Zeniths are great sets built for long reliable service. Keep at it and when you get the bugs worked out it will be a superb performing set.

maxhifi
01-17-2011, 11:53 PM
Thanks for the explanation! I actually just changed the zenith HV rectifier to a NOS GE, which may be what brought on the problem. I bought a set of tubes for the set, and changed all of them... thought it couldn't hurt after nearly 40 years, even though about half of them tested well into the green on my EICO 667. I'll put the old one back in tomorrow. I hope to keep the TV going until the picture tube becomes too weak to
be useful... at that point I'll have to search for a replacement tube, or a lower hour TV to get one from, which looks like quite a challenge in this day and age. I always assumed I could just have it rebuilt, when needed, so never paid much attention to securing a replacement.

old_coot88
01-18-2011, 10:16 AM
To expand a bit on the blooming problem (no pun intended:D), as the HV drops, it is "attracting" and accelerating the electron beam less and less, allowing the deflection angle to increase to the yoke's full deflection ability. Raster size is actually a balance between the HV and the yoke's deflection power. Since color CRTs draw much higher beam current than B&Ws, they require a much "stiffer", regulated HV supply. Bill(oc)

maxhifi
01-18-2011, 08:34 PM
I put the Zenith tube back... and problem solved. I wonder why the new tube was weak? This Zenith does not have a regulated HV supply, maybe it can get away with it on account of its small size?

Simpsons are on now... I can't believe how good the colour is with new tubes... set has a new lease on life.

maxhifi
01-19-2011, 01:41 AM
This TV is going to drive me crazy, but not before I get it sorted out. I've noticed a new problem with it. On some stations, when there's a lot of white in the picture, it tends to flicker... it's especially noticible with white text, and at the top and bottom edges of the picture when there's a 16x9 program playing. I don't remember it always doing this.

maxhifi
01-19-2011, 01:36 PM
Put the original 6MV8 Zenith sync separator back, and worked the AGC control back and forth a bunch of times to clean the tracks a bit. TV seems back to normal, or at least a lot better. Have learned a lesson here about not changing tubes all at once!

mwplefty
01-19-2011, 07:42 PM
Put the original 6MV8 Zenith sync separator back, and worked the AGC control back and forth a bunch of times to clean the tracks a bit. TV seems back to normal, or at least a lot better. Have learned a lesson here about not changing tubes all at once!

I have a 1972 Zenith 19CC19 (there's a picture in my VK photo album). I'm assuming that your set is a 1973 model judging by the chassis number.

maxhifi
01-31-2011, 12:41 AM
deleted

maxhifi
01-31-2011, 12:53 AM
Was waiting for a tow truck to show up at my house, with family member's car on the hook. Ford's 4.6L plastic intake manifold had decided to crack, and leak coolant everywhere. Shop wanted $1600 to fix, so I said bring it here and I'll do it, etc. Boring sitting around the house, so we decided to watch some TV.

"what's wrong with your TV's colour?"
"nothing, it's working fine, isn't it?"
"the colour is all wrong... look that is supposed to be purple, and it's blue"
"is it? looks fine to me.. uh oh"

Looks like I did the best I could, and got used to it.

OK found a station showing colour bars. Sat my Trinitron beside the Zenith, and no possible position of the RGB and tint controls makes them look the same on both sets. The (1979) Trinitron looks like a photo of a set of colour bars, but the Zenith will get either yellow or purple right, but not both at the same time! When purple looks good, yellow looks green, and when yellow looks good, purple looks red. Back to the bench it goes!

old_tv_nut
01-31-2011, 09:38 AM
1) is the monochrome tracking OK when you turn color all the way down?
2) could you post a pic of the Z and S side by side with color bars?

maxhifi
01-31-2011, 10:23 AM
1. I think it's good, but will check again tonight.

2. Will take some photos when home from work tonight. Should have done that yesterday!

maxhifi
02-10-2011, 12:00 AM
Finally found the charger for my digital camera.
Seems like today I was able to get the two to match a lot closer, but look how far off centre the Zenith's tint control has to be!

Apologies for my extreme lack of skill in taking photos of TV sets displaying a picture.

ctc17
02-10-2011, 06:56 AM
Looks good! Do the color afc alignment procedure in the sams and it will get all the controls centered out. No special gear is needed except that color bar generator. Its usually on the same page as grey scale setup

old_tv_nut
02-10-2011, 07:24 AM
A coupla comments:
1) The zenith looks like it has a little red purity problem (turning greenish) right down the center - I would try degaussing first. If that doesn't help, is the yoke glued on, or movable? Looks like it needs a nudge forward or back.
2) the Zenith has the typical color-correcting demod angles - makes the green bar a bit dim, the yellow a bit orange, and the magenta a bit redder - all designed so that a standard NTSC source will make the best flesh tones with the phosphors in that tube.

maxhifi
02-10-2011, 10:58 PM
CTC17

I'm still trying to get my hands on a test pattern/color bar generator - if I can't get one locally I'll go the eBay or classified ad route. That said, the TV sure looks way better now than it has in ages! I want to pick up a decent VTVM too. The Sams procedure looks quite straight forward.

old_tv_nut

1) The Yoke can be moved, and Sams has instructions for how to do this too.. I think it may be an artifact of the way I took the picture though, as in person red looks fairly even. I'm also afraid of messing up the convergence and not being able to get it back :)

2) Interesting... I've always liked the softer toned picture of this TV's chromacolor tube, but the dim green sometimes makes nature scenes look a bit less vibrant than they do on the Sony.

ctc17
02-10-2011, 11:36 PM
You don't need all that. Use the ntsc generator you show in the picture and just do the part where you adjust for the slowest moving bars and the adjutment to center out the tint control. Don't bother with all the voltage adjustments. Chances are if you get some old color bar generator it will have a drifted burst crystal and youwill align the set to that. Use your camera

maxhifi
02-10-2011, 11:58 PM
The sams procedure says to hook up a color bar generator, and adjust a specific coil to maximize the amplitude of the 6th color bar, and then has a waveform where all the different color bars are labeled. The other adjustments are voltage based, and there's only three coils to adjust with all else being fixed. I am assuming the test is based on the old type of color bar pattern where the bars have space between them, and don't really know how to apply this with the signal I'm getting from my cable box. Actually tomorrow I will scan the instruction page from sams and post it here, so you can see what I mean. Perhaps buying or burning a test pattern DVD would be a better option?

Looking at the picture carefully again tonight, I think old_tv_nut has a point about purity.

ctc17
02-11-2011, 12:15 AM
If you try and do all that you are going to regret it. Scan the schematic and instructions and I will help you thRough it.

maxhifi
02-11-2011, 01:29 PM
Sams info. If you need more of the schematic let me know.

old_tv_nut
02-11-2011, 07:07 PM
The final step with setting bar #6 to max is equivalent to setting for correct hue with the hue control centered - you don't really need a scope or even that particular type of color bars - can do it by eye if you know what the colors should be.

ctc17
02-11-2011, 09:30 PM
Yep, exactly. First thing I would do is remove C135 and C136 and check them. 135 is going to be real critical as to the function of the tint control and it may just be a good idea to replace both of those. Good chance everything will fall in line.
Other option is to put the tint control it center and adjust A24 until the tint is right. You would be compensating for drifted components.

maxhifi
02-11-2011, 11:09 PM
Fantastic... whittled a chopstick into a hex shape (need to order some alignment tools which fit!), A24 did the trick... tint control is in centre for same picture you see above. Thank you very much guys!

Next on the list is going to be getting the purity sorted out.

ctc17
02-11-2011, 11:28 PM
Make sure the degaussing is working. One easy way is to turn the green and blue screen down and the red up. Looks like you only need to move the two rings a tad to get red solid. Be careful because your going to trash the convergence. Dont go any further than moving the rings a tad without having a grid generator. MARK EVERYTHING!

maxhifi
02-11-2011, 11:44 PM
Deguass works. I can hear it when the TV is turned on. It's quieter than a new TV, but can hear the bump sound. Come to think of it, maybe it is too quiet... will check it out with a volt meter.

With that warning in mind I think I better hold off on touching this until I have a grid generator - Murphy's law, etc. May as well enjoy watching some TV before I screw it up again! I can't believe how good the colour is now with A24 touched up.. it seems like a new TV!

ctc17
02-12-2011, 12:07 PM
They can be amazing when working right. I have a zenith console with a funky color issue. No real greens and when I look at the set with the ntsc pattern like you are using yellow and green are pink and brown. Im kind of looking forward to fixing that problem.

If you are interested and working on old sets invest the few extra bucks and get yourself a ntsc patter generator. You can pick up one off ebay, mine are made by Leader.
Most of the tv shop style generators are pretty crappy.

maxhifi
02-12-2011, 12:47 PM
Something like this one?

http://cgi.ebay.com/LEADER-LCG-396-NTSC-Pattern-Generator-Video-Audio-Unit-/380315399681?pt=BI_Signal_Sources&hash=item588c907601

Looks like it has all the correct patterns, and is a bit cheaper than some of the other options. Don't want to comprimise usefulness by being too cheap though.

Once I have my Zenith in perfect shape, I would eventually like to get a tube console for upstairs, and tune it up to perfect operating condition. Would be nice to see a larger screen Zenith chromacolor. The RCA in your chroma alignment video looks like another excellent option. I want to be very careful about getting a console, because I tend to hold on to things forever, and whatever console I buy will be the one I intend to keep going until it's impossible, so it's got to be something capable of high enough performance I won't feel bad about continuing to invest time and money long past its real value.

ctc17
02-12-2011, 01:33 PM
Yep exactly. You cant beat RCA IMO. They do tend to have flyback issues is about all.

maxhifi
08-01-2011, 09:32 PM
Well, after months of good colour, a new problem has come up with the old Zenith.

Brightness was good, colour was good, everything looked great.

For the last while, the picture would occasionally jump in and out of focus.

Now, the TV still has a bright picture, but all the sudden became blurry during Hell's Kitchen. The focus control seems to have lost range... at one end, it's extremely blurry, and at the other still very blurry but less blurry.

Since the picture is still bright, am I right to think this might be the voltage divider at fault, or is this a sign of some other problem?

ctc17
08-01-2011, 09:48 PM
1304-3
Does it have the stick rectifier or the divider in the white tube? Ill see if I have the sams on that one.

maxhifi
08-01-2011, 10:05 PM
I have Sams (yes, it is 1304-3) for it already (actually paid to get it from Sams a few years ago, to fix a different problem) Can scan anything from it which would help.

Divider is white and rectangular, Zenith part 63-9893SE (63-9012) last time I had the back off it looked a little toasty but was still working fine. Looks more like a flat rectangle than a tube. I'll get into it and post a pic if it helps. Sams doesn't give the resistance value for the divider on the schematic.

ctc17
08-01-2011, 10:14 PM
Yea Im looking at it. Moyers should have that, if he has the oem part you may experience sticker shock. NTE made generic replacements that work fine. Its an NTE HVD-3 and it says its 240meg tapped at 40meg

You cant test it without special equipment. Look for the NTE one should be around $12

maxhifi
08-01-2011, 10:27 PM
Email sent to Moyers...

Simpsons are (well, till the focus issue) still looking great... not quite as good as your RCA, but it's looking good.

maxhifi
08-02-2011, 11:38 AM
This morning before work turned on the tv, and after it warmed up, everything came back into focus after playing with brightness and contrast. TV had been on for a couple hours last night when it failed, so may be a temperature related thing.

Focus control is still at extreme position. One odd thing now is when brightness is at full bright position, pic is totally out of focus and very, very bright. I am assuming this is a result of lack of voltage on the focus grid. Moyers has the nte part and i've got one on order. For 12 bucks it's worth a shot!

maxhifi
08-05-2011, 10:58 PM
Just after ordering the NTE from Moyer's, searched in google and got lucky with this one (last one in stock)

Figured I'd place an order since it has the right connector for the focus wire, so now I have two voltage dividers coming.

Looks like this shop might be a useful source for certain zenith and rca parts.

http://www.talonix.com/shop/item.aspx?itemid=13050

ctc17
08-05-2011, 11:10 PM
Thats cool. I have boxes of parts in the garage, I should start listing them all for sale on my site. Maybe I could find someone who needs on now and then.

maxhifi
08-05-2011, 11:51 PM
This stuff isn't getting easier to find - and it would force you to keep inventory of what you've got, possibly saving some time. I know I could have avoided buying lots of things if I actually knew what I have, and where it all is! Have you ever considered selling any of the sets on your site?

ctc17
08-06-2011, 10:46 AM
I have thought about selling some but hate to see them go into hands that will become frustrated with the issues and fish tank them. The truth is they will probably all get destroyed when the economy collapses and the roaming gangs of starving thugs take what they want and burn the rest.

I get emals all the time from people wanting to buy them for things like a part of a display in a vintage clothing store promoting their vintage line of chinese made trash. NO

maxhifi
08-06-2011, 01:13 PM
I see your point there, I don't think a bunch of 45 year old TVs are going to be the low hanging fruit for starving thugs though!

Plus I never liked the idea of mixing a hobby and work... there's no appeal to me in trying to profit from leisure activities, in fact, it'll just turn it into more work, which is hardly the point.

You've got some nice stuff on there, I'm tempted to make an offer on one of the table top colour sets next time I take a west coast road trip. The idea of buying something whose defects are known is very appealing. Gotta fit in the back seat of a Mustang.

ctc17
08-06-2011, 01:37 PM
We can get a console on the roof of your mustang, I have rope. Some of those table tops are on my panic checklist and are going with me to the grave.

Which type do you like? I can keep an eye out.

maxhifi
08-06-2011, 04:14 PM
Now that is funny, going down the interstate at 75 or 80 in the rain, with a console TV teetering on top of the mustang's tiny roof! I should mention I live in Canada! It's a couple days drive to get as far south as you are, but has made a fun trip in the past.

Best type for me is early 70s medium sized portable, 16 - 20 inch, hybrid or all tube. Brand would be Zenith or RCA, but I'm not looking for anything specific. A power transformer would be nice, but sure not essential. Emphasis on (potential for) picture quality above other factors.

maxhifi
08-17-2011, 12:18 AM
New divider came today - installed it. Focus problem instantly fixed.

Used recently acquired knowledge to check purity and convergence. Convergence was okay, purity was awful! Colours actually adjusted to NTSC now, finally accomplishing the original intent of this thread. Thanks to all who contributed.

maxhifi
10-01-2011, 11:13 PM
It's only been a month and a half?

Color has lately become intermittent

It comes on and off, with a gentle tap to the side of the set. Tried to sub all tubes related to color, and even the ones in the tuner and IF, to no effect. Color killer doesn't make a difference either.

Inspected for wires shorting and noticed nothing. Burst xtal? Sometimes even a tap to the coffee table will bring color back, or kill it, if it is working.

maxhifi
10-02-2011, 11:34 AM
OK never mind, I tried to sub the crystal with one from an Admiral console chassis - really messed up the colour, but it stayed on, red was blue, everything totally wrong. Tried to adjust A24 to dial it in without any luck.

Tacked in the xtal from an old Zenith console, and success, color is back, looks great, and no amount of tapping can disturb it. Don't have to hear my daughter asking why the people look grey again.

Electronic M
10-08-2011, 05:44 PM
After reading this I'm contemplating swaping out the crystal on my 71' Zenith hybrid. That darn thing has been slow to warm up it's color circuits for several years now, and has had problems with it's focus divider that at times have coincided in ways that have made me wonder if the two are related. I may change the divider soon so if the color issues continue after that I'll try other crystals while it is "on the bench".

maxhifi
11-05-2011, 06:44 PM
After reading this I'm contemplating swaping out the crystal on my 71' Zenith hybrid. That darn thing has been slow to warm up it's color circuits for several years now, and has had problems with it's focus divider that at times have coincided in ways that have made me wonder if the two are related. I may change the divider soon so if the color issues continue after that I'll try other crystals while it is "on the bench".


Well, it wasn't the crystal :) Sorry for late reply.
It's gone back to intermittent

I think it's something temperature related. It has NEVER lost color in the first 10 minutes of being on, and never with the cover off.

No time to dig into it right now, been messing patching a crack in my foundation before snow on the ground - also been working on new project, '69 Ford F-250 a friend wanted to get rid of. It opens a world of opportunity for getting consoles, etc.

Plus, I'm enjoying how my 6 yr old daughter responds to the loss of color.. before she'd complain, now she turns the fine tuning a touch and makes it work, ever 10 minutes. Somehow that's just enough to get the color osc. going again.

Electronic M
11-05-2011, 07:10 PM
I haven't gotten to my set yet so the reply was actually EARLY by a couple of weeks.

Your daughter sounds like a smart kid, just keep your fingers crossed that she never messes with the grayscale adjustments, etc on the back. When I was two I found a screwdriver and with in minutes I handed my folks the all the screws from the back door knob that I could reach, and so started my spree of dismanteling anything that I was not scared of.

maxhifi
11-06-2011, 12:44 AM
I haven't gotten to my set yet so the reply was actually EARLY by a couple of weeks.

Your daughter sounds like a smart kid, just keep your fingers crossed that she never messes with the grayscale adjustments, etc on the back. When I was two I found a screwdriver and with in minutes I handed my folks the all the screws from the back door knob that I could reach, and so started my spree of dismanteling anything that I was not scared of.

Well, experience is worth more than stuff, I think, even including my beloved Zenith. I can always put it back how it's supposed to be, but I can't force interest in anything. I'm glad she's looking at cause and effect instead of complainiing though, and with that attitude and a gentle touch I doubt anything will be wrecked by touching up fine tuning here and there.

When I was a kid I'd always wait for my parents to go out somewhere, so I could pick something to take apart and get back together before they returned. The only thing I took on which I never could get back together was the sewing machine... they had to get it professionally repaired, and I didn't hear the end of it for a while.

This TV has thrown me for a loop here and there, but I don't want to give up on it. Next step is probably replacing all the caps and checking all the resistors in the burst oscillator circuit. So far have done

-sub osc tube with NOS
-replace xtal
-re-solder connections on coils

Will throw in those parts next time I order from mouser or etc.

ctc17
11-06-2011, 09:13 PM
Hmmm, maybe its not in the color demod circuit at all. Maybe its something in the front end or some kind of interference.

maxhifi
11-06-2011, 10:11 PM
Hmmm, maybe its not in the color demod circuit at all. Maybe its something in the front end or some kind of interference.

Decided to do some digging. The problem had by now got bad enough it was happening all the time, and tapping the side of the TV would toggle the color on or off.

Took the back off the TV, and started tapping things, trying to figure out what is turning the color on and off, and I noticed something.

The color control is connected to the chassis with a shielded cable, which terminates in two crimp on connectors. These connectors slide onto the top part of Zenith's terminal strips. The signal connector was slid nearly all the way off, and barely making contact. This connector is very close to the recently replaced focus divider, and I bet I knocked it when I did that job.

I tightened the connectors with some pliers, sprayed some contact cleaner, pushed them back on their respective terminals, and then powered up TV. Seems that tapping the tv now has no impact on the color at all. Time will tell if I fixed it, but it looks good so far.

ctc17
11-06-2011, 10:24 PM
:thmbsp::thmbsp:

Good Job. Sounds like that could have been it.

maxhifi
11-06-2011, 10:42 PM
:thmbsp::thmbsp:

Good Job. Sounds like that could have been it.

Thanks! Let's hope so. Took me a while, and some wrong turns to discover it.

maxhifi
11-14-2011, 09:20 PM
Quick update - still working perfect, can finally say problem solved. Time for something new.to work on.