T.v works fine for a while then goes to thin rainbow across
middle of screen. If you turn it off for a while it will
come on and work fine again for a while. It has a thin bar of color all the way across the middle of the screen.
Please help what could be wrong?
The signals on each projector are the same and swappable. you can use a signal cable or plug off of another gun like green to trouble shoot with to see if the red signal is the problem.
also press on any chips or plugs to make sure they are seated good on the board inside TV.
Also on the pc board inside diods and regulators break down with heat when they are going bad.
I have worked on projection displays for about 17 years 20years electronic. and this sounds like a vertical deflection amplifier problem. this is if the lines or the rainbow you said that you see are horizantal.
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Lines going across is a little vague but there is always the problem with the electrolytics (caps) around the vertical, be sure and get the one on the power supply too. Just change all you can find(usually 4-5). Thre are 2 convergence ic's if you didn't change them both, resolder the other one.
Then check the value on R519 for me.
If the lines are thin and close together running horizontally, it may be the vertical driver, but that usually takes out the resistor and sometimes the diode in the B+ for the vert. Also you must replace the caps that caused the problem in the first place.
Sounds like the vertical control IC has gone out. Replace IC N301 (TDA8351) and check or replace R370 (1ohm), R371(33ohm), and R380(1ohm). This shouldn't affect the sound but once you get video you might figure out what is wrong with the sound (control setting).
The TDA8351 crosses to NTE7156 and shouldn't run you more than $10.
I just fixed this problem on my neighbor TV. I don't have a manual or schematic, and didn't pay any attention to the reference designators, so I will just have to describe it. The problem was a bad solder joint. Visible thermal fatigue. Looking at the main board, (didn't even need to slide the cassis out). There is a small, narrow, vertical board in the center, adjacent to the yoke connectors with a funny looking little transformer on the very top. Check the connections on that. -John