About two months ago my TV started to display a solid white background with no retrace lines. The sound works fine along with all menus and tv features. Ex: I can change the channels and the channel number will pop up in the upper right hand corner in full color or the menu system will display in the spectrum of colors as intended. Sometimes the tv will lose the white screen and display the correct image, however this is rare(It works for minutes, days, or weeks at a time on rare occasions). PIP works well and it displays the seperate images PIP is supposed to look, however when PIP comes on the background other than PIP turns from white to a medium gray. The Svideo(90) and other inputs are also white.
The TV is less likely to display full color when its been sitting and its cold. There is no smell or visible trace of burnt components.
When I first started reading your post I thought video amp on CRT board. But reading the rest, it sound as though your jungle ic has gone south or going that way
"Other than power supply problems, this is the second most common circuit to give people problems on our sets made in the last 5 years. If you have high voltage and vertical deflection (as you indicated) the unit is probably in what we term as 'IK blanking'.
The jungle IC sends a 60us pulse in the vertical blanking area in order to monitor CRT cathode current, thus maintaining white balance. Each color drive output has its own pulse in this area (Red=line 17, Green=line 18, and Blue=line 19. These pulses are them matrixed and returned to the jungle IC to be monitored. If one or more of the pulses does not return (or is very low) the jungle IC will keep the video off. Bad video drivers, weak CRT cathodes or faulty IK pulse return circuits will cause this symptom".
Here's how to find the cause: Even though the video is off, the Jungle IC is sending the pulses to the CRT board. Measure each of the cathodes with a scope. At vertical rate you should see a 60us pulse at each cathode about 20-50 volts in amplitude. What we're looking for is one of the cathodes to either have an extremely large pulse (in comparison to the other two) at about 150 Vp-p or having no pulse at all".
If one cathode has no pulse, troubleshoot the driver circuitry for that color.
If one cathode has a very large pulse, the cathode is weak or the return pulse is not making it back to the Jungle IC. To tell if the CRT is bad, turn up the screen control and see if you get a raster with one of the primary colors missing. It should be the color that you saw the large pulse on. If the raster is white or is slightly dominant in one of the primary colors, the CRT is probably OK. Troubleshoot the IK return buffer transistor and associated components for that driver.
If all 3 cathodes have a large pulse (150VPP) Then check the following:
The IK buffer transistor which is sending the combined pulses out of the CRT board (all three must be present here and at least 700mvpp).
The screen control is turned too low.
G1-G2 short or leakage. this will be evident by G2 voltage dropping drastically while the CRT board is mounted on the tube and raising when removed."
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