Thanks for the tuner gear tip!

Dave

Looks like a decent pic already, I think you'll find the ghosting is an IF/tuner issue. Probably alignment time.

I wonder if a Velcro strap wrapped around that cloverleaf would hold it in place?

Yep, looks like most of it is in the IF stages. Here is a picture of driving the tuner input to the first IF with 45.75 MHz modulated with video. And another driving composite video into both the sync video takeoff and into just after the video detector. There does seem to be a little undershoot in the video stages, or maybe just from the unterminated VA62 video signal cable I used. My cheap camera white balance changed colors between the two pictures, it looked the same to my eye.
Dave

That would help firm up the angles between the pole pieces. I also see that the green is titled back some. Maybe I need a ring of plastic to hold then in the same plane.

Dave

Before even thinking of messing with alignment, try subbing the last IF tube. It can cause ringing that can be mistaken for misalignment.

On that stripped gear, your shrink tubing collar is a good idea in addition to epoxy. "Belt and suspenders" redundancy.:nerd:

I tried changing each and all of the three IF tubes with some change to the ringing. Three new tubes in place of the originals does have a bit less ringing. I will try an alignment this weekend.

I'm gonna add the epoxy to the gear too.

Dave

maybe some delay line ringing?

I found that all of the Zenith color roundie convergence coils are interchangeable. The latter ones might not aesthetically correct but at least they are better made and more rugged.

The epoxy trick would not fix the broken fine tuning gear on my Zenith. The reason was that the plastic appeared to have shrunk and epoxying it would have left a considerable gap between teeth at the break. What I did was to cut an O from the end of a BIC pen, the inner diameter of which was roughly equal or slightly smaller than the gear when compressed to close the gap. With the fine tuning shaft removed, I heated it with a large soldering iron until it would just begin to melt the gear and then with gear compressed around the shaft, I slipped on the BIC ring to hold the gear compressed.

Fix ensured the gear melted into the splines and there would be no gap between the teeth where the break was. It was bit fiddley to fabricate and install, but the result worked like a charm.

I just tried adjusting the delay line termination potentiometer. It did not affect this ringing.

Post #44 shows pictures of test pattern video driven into the first IF showing ringing and then composite video driven into just after the video detector that does not show nearly as much ringing. Sure seems like it's in the IF stages.

Dave

oh my yes, I missed that. I wonder if all the little ferrite beads are in place etc. on the filament leads? My later zenith (24MC32) has several IIRC on the IF filaments. Mine also has a 22k resistor across the secondary of the IF before the 3rd IF tube. Wonder if maybe that has drifted high? I assume its there to damp out oscillation.

My first two IF stages filaments have a ferrite bead, as well as a couple more beads in the filaments some color circuit tubes. I did check and replace out of tolerance resistors in the IF stages, being careful to match lead dress as close to original as possible.

Before I started to do an IF alignment, I took some pictures of some video test pattern waveforms taken at the input to the first video amp. All the tuner and IF tubes have been tested and swapped with not much difference in the ringing. I used my Sencore VA62 to generate a channel 3 RF signal displaying the single vertical and horizontal line cross. The first video amp input scope picture shows the ringing. I then set the VA62 to generate its 10 section multi-burst which is a set of white and black vertical lines of increasing frequency from 0 to 4.5 MHz. The second picture shows the poor frequency response.

Here is a picture of the SAMs IF frequency response. Figure 1 is the third IF and figure 2 is the first and second response. The next picture shows the third IF response is pretty close to what SAMs shows (you have flip the plot horizontally to match my scope). The next picture is what I got for the first and second IF response. Its way off. The response at the 45.75 MHz marker shown should be much lower amplitude. Following SAMs alignment I tried to adjust A6, the 41.25 MHz trap and found it very hard to turn because its core was coming apart. I pulled the chassis, removed the coil, and removed the core. One end had two small pieces broken off. I tried a shorter ferrite core to see if the coil form was too tight. It was very tight. I ended up finding that a 1/4"-28 tap matches this ferrite core. So I tapped the coil form as shown in the next picture. The last picture shows the shavings removed from the coil form. The small ferrite core now threads nicely though the core. I am trying to glue the two small ferrite pieces back onto the broken core. If they hold, I will invert the core so that the broken pieces will be at the end that is not usually used for adjusting. Anyone know of a place to buy 1/4" threaded ferrite cores?

Dave

I've got a bunch (~ half of a cigar box full) of ferrite cores - how long?

I always pulled the cores from sets I junked - and at my dad's shop, I was the TV stripper/parts puller/gofer. I probably have junked over 300 sets in 30+ years. First we saved everything, then just certain chassis, then just modules, and finally, only good chassis/CRTs. My user name comes from my attitude - if you find it, keep it. Someone, somewhere will likely need it.

Cheers,

Nice. All I could find online were ferrite interference filter beads. I need two 1/4" by 5/8" long cores. If you have them, let me know the cost and shipping charges. Thanks.

Dave

I am just curious as to how this aspect panned out for you. I am working on a similar vintage Zenith and your findings are almost identical to what I was finding in my set except I can't get 190mA. More like 200 or maybe 210 at 110V. My flyback seems hotter than I would like it to be after about 30 minutes of operation. I am waiting on a replacement socket for my HV rectifier which was burned up and the 1W resistor was open (blasted in two).

I had long been searching for the source of a very light HV hissing that was intermittent. It couldn't be seen down inside the insulating cup of course. I think that we should be able to achieve correct cathode current at full line potential. Like you, I used a variable source to control this, but I don't think it would be necessary to use that or alter the line voltage in a healthy set. Also, I found that just having the raster fill the screen is not guite all my set needs. The higher line voltages (above 110V) around 115V or up give a much crisper or clearly defined picture once video comes into play.

PM sent.

I have been attempting to align my IF so my set has been on for up to a couple hours at a time. I still have my Simpson 260 in series with the HO cathode and have been keeping an eye on it. So far it is holding at about 190-195 mA. I turned it off after it had been on for over an hour and felt the flyback. It was certainly warm but not burn you fingers hot. I will use an IR thermometer on it next time I have it on for a while and report the result. If it would help, I can also take some voltage readings. You may want to replace all of the capacitors in the HO section and verify that all of the resistors are within their tolerance. A leaky HO grid cap could elevate your current.

Dave

Thanks very much for your kind help!

Dave

I put my glued together ferrite core back in its coil and put the set back together. Then I tried using the Sams IF alignment procedure. It did help some. The Sams procedure tells you to use a demodulator probe at points after the detector. This did not work for me. I used a normal scope probe and got reasonable waveforms. The Sams also shows three IF sweep curves but the alignment text only refers to two of them. After the Sams alignment procedure I did get rid of the ringing in the video but also lost color. I could not match the curves response in the 42-43 MHz range. I used the VA62 multi-burst and tweaked the IF adjustments to get more color signal frequencies through (3 to 4 MHz) and got the color back. But when looking at a channel 3 RF signal I got a noisy picture.

I looked through the R.L. Goodman Zenith Color TV service manual and found a more detailed IF alignment than the Sams. It showed similar sweep curves but its procedure referred to all of them. So my next attempt will be to use this alignment procedure. The procedure is general to cover several Zenith sets, including the 27KC20 (which has very similar design and is the successor to my 29JC20), so some test point designations require translation to use on my set. I am no whiz at aligning sets, but I am determined.

Dave

You may also want to check the cathode current of the 6BK4. The Sams for my set says to adjust the HV to 24kV and make sure it is at least .9 mA. If I recall right, mine was about 1.9 mA with 24 kV. The schematic showed a 25-26 kV voltage and the 21FJP22A spec has a maximum rating of 27.5 kV. I adjusted my HV for 25.5 kV. I noticed that my HO cathode current went down with the higher HV setting. Maybe you can reduce your HO current by raising the HV, if your CRT and set will permit it.

Dave

I used the R.L. Goodman Zenith Color TV Service Manual IF alignment procedure. It took three iterations but the result matched the sweep diagram pretty well. Here are pictures of the Goodman response curve, the result I got, and the Multiburst response. The alignment got rid of some of the ringing seen on the CRT, but what was left was a dimmer wide repeating pattern. Here is a picture of the video waveform before and after the delay line. I found that the delay line termination potentiometer was open. I opened it and cleaned off the oxidation. I then worked fine, so I put it back in.

Here is a picture of the single vertical and horizontal convergence pattern that had so much ringing when I first powered up the set. The color would initially work and then fade away when I first powered on the set after the recap. I found that the second chroma output was fading. It is gain controlled using a bias from the color killer modulated by Zeniths Automatic Color Control. For now I cheated and just put a resistor in parallel with part of the bias filtering to increase the gain to keep the color working. It still kills the color on black and white video and seems to work fine otherwise. Here are some pictures of video through the tuner. I may make one more pass through the IF alignment and then do the audio alignment. The audio has a little distortion in it at the moment.

That looks really good !

I'm wondering about the blue dipping on both ends at the edge of the screen.....
Could the zip tie around the convergence magnet assembly be changing it's
orientation from a perfect perpendicular to cause the dipping....?

Imagine if the magnet was forced towards the back of the yoke, and not
straight up and down, then if it is trying to make the line straight, but
orientation is wrong, pushing the line lower on the ends.... If the magnet's
orientation was forced away from the yoke would the line go up at the ends
if it's all working correct....?

Or am I all wet, and it's most likely a aging part, or the best it's gunna get....


.

The three coils on the convergence board are blue line adjustments. One of them (I forget which one) is for the horiz blue line.
A word of caution: one of those , if you back the slug out too far, will roast one of the pots. So go easy.

Hi !

Not what I was getting at..... On the first page of this thread a picture is posted of the
3 convergence coils held on the neck of the picture tube with the help of a zip tie.
I was just wondering if this method changes the orientation of the coil, with respect
to the electron gun, and it is either tilted towards the yoke a little, or away from it
and results in the downturning of the blue line in the cross pattern on the screen
in a posted picture on this page of this thread....
Left most picture post #64.

.

Take a look at post #39. I have removed the tie-strap and am experimenting with some springs to try to space the pole pieces closer to correct. The green plastic is cracked and is allowing that pole piece to tilt some. More work will be required to position them properly. I would try to find a Zenith replacement part but this set has already had this plastic piece replaced before and it has failed twice. Also, I have only done a very quick convergence on the set, as I have been moving the chassis between the work bench and the cabinet as I test and fix problems. So yeah, its nowhere near done yet. I just wanted to show the results of the alignment, the delay line terminator repair, and the color kludge. At least it now has a good start on a watchable picture.

Dave

Thanks for the warning. I started my first convergence by trying to center the convergence adjustments. I need to replace a ferrite core in one of those coils, so the convergence you see now is just enough effort for testing and fixing the rest of the set.

Dave

Sorry there Z I guess I missed a few pages in the middle of your story.....
In #39 you have the assembly removed. A possible fix could be laying it down like
you did, put it in as close a position as possible, and tracing out the outside
perimeter of it, and making a plastic holder for it - a big circle - with cutouts
for the "cloverleaf" and silicon glue the plastic circle to the CL - maybe put shims
along the way to get position just right..... Might be more rigid than springs....
and not interfere magnetically..... 1/4" or thicker sheet plastic..... Maybe
even polypropylene, or polyethylene.... A little softer, and immune to a lot of
stuff..... Give it less brittle start....

.

I certainly need something to keep them in place better than just the springs.

I got better results with another alignment. Here is a picture of the sweep with the marker at 42.75 Mhz and 45.0 Mhz. And a picture of the multiburst showing 0-4.5 Mhz making it through the tuner to the first video amp. This alignment also reduced the ringing of the single vertical line, as shown in the magnified scope image in the fourth picture. The last is what this alignment looks like on the CRT. I think this alignment is a keeper.

Dave

I went through the audio alignment which fixed the distortion in the sound and increased the volume a lot.

Neither of the yoke centering adjusting strings would move. I took the yoke off the CRT and was then able to move the strings a little. Working them back and forth a bit seemed to free them up. I put the yoke back on and fired up the set to try to use the centering strings. The strings moved the centering rings but for some reason the image on the CRT does not move. I wonder what I am doing wrong. The image does fill the CRT and the centering is not off by a lot. It still would be nice to get it centered though.

Dave

Your 29JC is looking good. I have the manual scanned for it I could send you a link to if you don't have it. Just PM Me.

I'd be interested in a copy too.

The Zenith are prone to line pairing, I've found you can improve the interlace by fine tuning the Vert hold. They say increasing the integrator resistance also helps.

Could you point out which resistor(s) using the attached Sams diagram? I have not replaced the K1 and K2 networks. I do see that the odd and even horizontal scan lines seem to be offset horizontally from each other when I look at the color bar pattern. If you zoom in on the color bar patter in post #35 you can just see the offset. Thanks.

Dave

I found a note in Goodman about the cause of the centering strings to not adjust the centering. The glue fails and the magnetic rings no longer move. I am going to try to re-glue mine.

Wow, cool! PM sent.

Dave

I took my centering rings out and re-glued them. Here are some pictures. There is a plastic ring at the end of the centering strings. The plastic rings are glued to the magnetic rings. The glue on mine had failed. I used some epoxy to glue them back on. There is a spacer between the magnetic rings and thick paper ring with tabs that holds them in place. The centering strings now work fine.