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  #61  
Old 02-10-2015, 06:40 PM
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Zenith6S321 Zenith6S321 is offline
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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
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  #62  
Old 02-11-2015, 06:21 PM
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Zenith6S321 Zenith6S321 is offline
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Quote:
Originally Posted by Tubejunke View Post
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.
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
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  #63  
Old 02-14-2015, 07:44 PM
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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.
Attached Images
File Type: jpg Goodman-Overall-Sweep-Response.jpg (113.1 KB, 14 views)
File Type: jpg Overall-Sweep-Response-Result.jpg (117.8 KB, 18 views)
File Type: jpg Multiburst-After-Goodman-Alignment.jpg (119.1 KB, 15 views)
File Type: jpg Before-DelayLine.jpg (120.5 KB, 13 views)
File Type: jpg After-DelayLine.jpg (118.2 KB, 12 views)
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  #64  
Old 02-14-2015, 08:04 PM
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Zenith6S321 Zenith6S321 is offline
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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.
Attached Images
File Type: jpg After-Goodman-Alignment-and-DelayLine-Pot.jpg (128.6 KB, 39 views)
File Type: jpg 100_5004.jpg (63.9 KB, 55 views)
File Type: jpg 100_5016.jpg (70.4 KB, 49 views)
File Type: jpg 100_5033.jpg (64.3 KB, 35 views)
File Type: jpg 100_5022.jpg (66.3 KB, 52 views)
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  #65  
Old 02-14-2015, 08:36 PM
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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....


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Last edited by Username1; 02-14-2015 at 09:13 PM.
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  #66  
Old 02-14-2015, 09:30 PM
old_coot88 old_coot88 is offline
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Quote:
Originally Posted by Username1 View Post
...
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....?
.
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.

Last edited by old_coot88; 02-14-2015 at 09:33 PM.
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  #67  
Old 02-14-2015, 09:39 PM
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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.

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  #68  
Old 02-14-2015, 10:05 PM
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Zenith6S321 Zenith6S321 is offline
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Quote:
Originally Posted by Username1 View Post
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
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  #69  
Old 02-14-2015, 10:12 PM
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Zenith6S321 Zenith6S321 is offline
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Quote:
Originally Posted by old_coot88 View Post
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.
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
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  #70  
Old 02-15-2015, 07:29 AM
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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....

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  #71  
Old 02-15-2015, 05:56 PM
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Zenith6S321 Zenith6S321 is offline
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Quote:
Originally Posted by Username1 View Post
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.
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  #72  
Old 02-15-2015, 06:28 PM
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Zenith6S321 Zenith6S321 is offline
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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
Attached Images
File Type: jpg Best-Align-42.75Mhz-Marker.jpg (119.6 KB, 11 views)
File Type: jpg Best-Align-45Mhz-Marker.jpg (120.8 KB, 13 views)
File Type: jpg Best-Align-Multiburst.jpg (119.8 KB, 14 views)
File Type: jpg Best-Align-Result.jpg (123.9 KB, 43 views)

Last edited by Zenith6S321; 01-21-2017 at 05:33 PM.
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  #73  
Old 02-15-2015, 06:39 PM
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Zenith6S321 Zenith6S321 is offline
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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
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  #74  
Old 02-15-2015, 10:40 PM
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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.
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File Type: jpg scan.jpg (65.5 KB, 26 views)
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  #75  
Old 02-15-2015, 11:24 PM
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Quote:
Originally Posted by damen View Post
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.
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