This is a 90's 25 inches tv set model Z25X22S (GX generic chasis) it came with horizontal retrace lines as if G2 screen control would be too high, I checked and it was normal, I changhed the video B+ capacitor and it make no effect, then I checked all video and smps B+ waveforms and all seems to be normal, I really don't know what I'm missing, I know that this is an old tv set but maybe someone of you expirienced guys had have the same problem and know this case, any posible help is really apreciated, thanks.
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Re: zenith tv, video retrace lines.
How is the 200 volt supply to the video output transistors??
measure the collector voltage of the video output transistors with the crt board on and off the crt. if voltage goes up when crt board is off then crt shorted
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Retrace lines. If you wish to get some details; check the site linked here. Pull up older posts. Surf the site with patience. http://electronicshelponline.blogspot.com/
Search the site with keyword 'retrace lines'
Most "modern" CRT TVs have automatic color biasing which means a complete of manual control. Depending on how your set is manufactured, it may have a control for each color located on the neck board for adjusting the drive to each of the CRT guns.
What you're seeing is called 'retrace' and you're correct that this has to do with color blanking. The most common issue causing 'faint' retrace is too much drive to one of the CRT guns. Hopefully, your set has an adjustment to back off the drive for the green gun. If not, this can be the result of a bad capacitor or leaky transistor in the green circuit.
If all else fails, locate the SCREEN of G2 knob on the back of the flyback transformer and back it down a touch; sometimes this is all it takes.
1st set Brightness and Contrast settings to 50% at tv menu.
You need to cover 2 CRTs with any thing like thick paper while adjusting 3rd CRT.
For example, lets adjust Red CRT G2 volts, Select audio-video input 1 and cover green and blue lens with paper note-book and rotate Screen control up to level where you see retrace lines on projection screen, now decrease screen volts (G2) so retrace lines disappear and projection screen should be blank.
Now do same process with green and blue adjustment while other lenses should be covered.
Im not sure I conveyed it to you properly or not because English is not my 1st language.
This is a problem with the vertical circuit. If you can solder, you should be able to fix this. With teh unit unplugged, open up the back and locate the vetical IC. This should be a small flat IC attached to a heatsink with about 9-11 pins. It may be marked LA7837 or something similar. Try resoldering hte pins. If that fails to resolve the problem, replace the IC. I will look up your specific model and try to get more details.
On the inside of the TV, there will be a knob with a RED cap on it, labeled vertial position. (it actually looks like a variable inductor)
With an allen wrench (possible 1/4) give it a half turn in either direction and see what happens. On the Z25x22S model, the vertical and horizontal position adjustments should be right next to eachother, but on the model i worked on, there was no variable pot for the horizontal position.