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  #1  
Old 02-13-2011, 09:09 AM
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colortubeman colortubeman is offline
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Problema NTSC ZENITH 16Z8C50

Hello everyone, I apologize if the text is difficult to understand because it is filled with a translator.
I'm an Italian collector of old color TV (colortubemania in youtube) and now I'm trying to fix the chassis ZENITH 16Z8C50.
Unfortunately, the TV has been tampered with and many components have been removed on the decoder to match the NTSC color system PAL Italian with an external adapter that I did not.
Now, as the video source in Europe you can remodel in NTSC I would reconstruct the original.
Unfortunately the schematic I would not find that here in Italy if you can help.
Now I have a similar schematic to the frame 15V6C15 but definitely not the same because the NTSC does not work .
The TV was not used much and I think that the valves are in good condition.
The image changes color in the sides of the screen while it is ok in the middle
Can you help me find the schematic and see where the problem lies?
Thanks so much for any advice that I give.
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  #2  
Old 02-13-2011, 09:23 AM
DaveWM DaveWM is offline
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have you tried doing a purity setup?
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  #3  
Old 02-13-2011, 10:23 AM
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No the purity end the b/w image is ok the problem is located in the NTSC decoder..........
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Old 02-13-2011, 12:20 PM
ctc17 ctc17 is offline
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That is defiantly purity, its an adjustment not something you need the schematic for. It comes from moving the set around.
First check the degaussing circuit and make sure you have no magnetic sources nearby like big speakers.
I can make a video on how to check and adjust the purity later, i have a zenith here that needs it bad.
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Old 02-13-2011, 12:38 PM
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high purity and controlled using only the white raster with red cannon.
I have also demagnetized with an external demagnetizer.
The problem is that I have reconstructed on the circuit and without the layout of the model can not run well.
Surely theres a problem on the piloting of the burst may signal the horizontal oscillator is not ok.
I've tried in many ways even with capacitors applied but you get only a mismatch of color, but the problem remains.
I'm sure that if I do well in the scheme just to make it work maybe some else is missing capacitor but I can not figure out where.
I copied the scheme to rebuild it is another model of ZENITH and certainly is different even if the valves fitted.
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Old 02-13-2011, 12:57 PM
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Just an observation for us here trying to be helpful..Look close at the screen shots and see the wavy pattern that all the colors are following? If it was just a purity issue the screen "impurities" would be more "blotchy" with no real pattern. See what I mean or am I off here?

I believe the initial approach would be to observe the screen with no signal input what-so-ever and see what we have. What does a blank raster look like? And the color turned down all the way/off.
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Old 02-13-2011, 01:07 PM
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miniman82 miniman82 is offline
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Looks like the local 3.58mhz oscilator is drifting to me.
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Old 02-13-2011, 05:03 PM
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marty59 marty59 is offline
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Quote:
Originally Posted by miniman82 View Post
Looks like the local 3.58mhz oscilator is drifting to me.
I'd kinda agree to that except that color bars will run horizontally...maybe some B+ filtering or some sort of grounding issue around the burst amp/oscillator, something open?
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Old 02-13-2011, 05:47 PM
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First of all thank you all for giving me reply.
I think the problem lies in the stadium at 3.58 but the oscillator waveforms measured with the oscilloscope are the same as those described in the diagram I have schematic of mod.ZENITH 15V6C15.
The filtering of the B + I checked, also for safety I added one capacitor 450v 150mf in +B but nothing has changed.
The color is stopped that you can see how the pictures and does not move up and down of the screen.
is stable are different colors on the sides of the screen because maybe the oscillator operates at a multiple frequency of 3.58 what do you think?.
Unfortunately I need to reconstruct his original scheme of the model otherwise I can not understand it because something is definitely different from the drawing that I used now to restore it.
Please help me with original schematic ZENITH 16Z8C50.
Thanks again.

AscoltaTrascrizione fonetica
Dizionario - Visualizza dizionario dettagliato

Last edited by colortubeman; 02-13-2011 at 06:00 PM.
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  #10  
Old 02-13-2011, 06:36 PM
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Steve McVoy Steve McVoy is offline
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Your set is in Sams folder 1074-3. You can buy it at:

https://www.samswebsite.com/
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  #11  
Old 02-13-2011, 08:39 PM
ctc17 ctc17 is offline
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Ok, yes you are right, was looking at the pix on my phone. It does look like the osc is drifting, maybe something with the color afc?
That could be real challenging yet fun to figure out if its due to modification.
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Old 02-13-2011, 09:28 PM
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reeferman reeferman is offline
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Colortubeman. I have the schematic. I have sent you a private message.
Phil
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  #13  
Old 02-14-2011, 03:35 AM
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colortubeman colortubeman is offline
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hello Phil thank for you interest for help me.
I hope I can reciprocate if you need some European tv schematics.
My mail is :
fabionet71@libero.it

thank you
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  #14  
Old 02-14-2011, 06:51 AM
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reeferman reeferman is offline
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Coming your way. Good luck.
Phil
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  #15  
Old 02-14-2011, 07:34 AM
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Hello Phil you are the BEST.
THANKS
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