I have a zenith model sj7765bg almost 20 years old. About 2 years ago i noticed there seemed to be too much blue in the picture. i did a color temperature adjustment and it was ok. shortely after the blue increased again. i adjusted the temp again, but shortly after it was too much blue again so i thought i would just live with it. about a month ago the blue got really intense and then the tv shut off completely. i unpluged it and turned it on again and it came on for 2 seconds and then shut off. now i get no picture at all but sound is still there. i replaced the flyback, hot, and voltage regulator i checked the diodes and capacitors in the horizontal circuits and power supply and they seem to be good. i checked the chopper transformer windings and could not find any shorts or opens. i have noticed a high pitched squeal coming from the board after i plug it in, but this disapears after a few seconds. it never did that before. i was wondering if the picture tube could cause a problem like this
Televison & Video - Zenith
Answers & Comments
I think you may have two separate issues.........the picture tube can arc and cause components to fail.........but it will usually come on very bright ,then shut down. The squeal may be coming from the power supply......that is telling you that it is sensing an over current. Let us start by disconnecting the Horiz out collector.......start the set see if the squeal is gone and do you have 130 v dc at the collector unsoldered pad? If so.........you will have sound now too. Make this check and I will reply with next step to help.......thx!
It could be a bad picture tube, or a bad driver transistor on the blue gun. there are 3 transistors on the crt board that are usually the same type (sometimes all 3 are in 1 big ic). usually before it goes all the way out, you can just swap them around and see if the problem switches to red or green, but since its totally out now, maybe that transistor went bad. look at the resistors hooked to it as well and see if any are burnt up. i'd say that if this transistor doesn't fix the issue, it is probably a bad CRT or blue gun in the CRT and could be the end of the life.. but hopefully its just this transistor. Get the # off of it and try to find a new one
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If its getting too much blue, its probably a bad CRT.. check multiple inputs and check the menu and see if they are effected by the blue issue too. If so, the CRT is probably the fault. A lot of these would go about 20 years and the guns start to wear out and cause issues. If not all of the inputs or menu are effected, it could be back in the video signals somewhere. I believe most of these sets you can get board for still, but the whole board would probably be $100 or so, might not be worth sinking all that into it. Let me know what you find..