anybodygoing to answer?
Categories: Televisions and Projectors
SOME TIMES IT TURNS ON AND OTHERS, I WHISH IT DID.
IT TURNS ON FOR ABOUT 15 TO 20 MINUTES AND IT TURNS OFF. BUT WHEN I SET A FAN IN THE BACK IT STAYED ONN TILL I TURNED IT OFF, THEN THE NEXT DAY IT WOULD NOT TURN ON AGAIN. COULD IT BE THE TRANSFORMER ? BT00161
I'm sorry you've been unable to get an answer to your question. It's important to note that TechLore is a consumer community, and while I'm sure they all want to help, technical repair questions such as yours are often too difficult to answer. Your question, though a good one, would probably be best answered by a qualified technician.
Perhaps someone with the right knowledge may find your thread and be able to help you. Until then, I wish you the best of luck in solving your problem.
You could have any number of problems. Unfortunately these sets have a total of 15 different 'shutdown' triggers, if any of these is detected the set either refuses to come on or instantly clicks off as soon as a fault is detected. Take heart though, this is for your own good, and the good of the TV, some of these failures could cause fires, permanent damage to the CRT's (pix tubes)and other very expensive parts, or the production of hazardous levels of X-rays.
Now for my standard 3 questions:
1)Do you know how to solder?
2)Do you know what an electrolytic capacitor looks like?
3)Are you aware of the hazards involved in television repair?
If you answered 'NO' to ANY of these questions, DON'T ATTEMPT to repair your TV.
TV's have many componets that are capable of holding nasty voltages LONG AFTER THE SET IS UNPLUGGED! Your SURVIVAL, and that of the television, depend on your ability to identify and handle these componets correctly! This goes especially for Projection TV's.
You have been WARNED and I will not be held responsible in any way for your actions or ignorance of these dangers!
If you are technically competant and have the skills to solder you might try resoldering the convergence outputs, vertical output power supply and horizontal sections. This might solve your problem. If this doesn't work, it's going to take a lot of expensive test equipment, and time, to track down the source of the shutdown trigger.
---------------------WARNING!! ------------------These parts are CRITICAL, improper handling and/or soldering methods can cause PERMANENT and very costly damage to the set.
I'm not trying to be pesky with the warnings here but I feel that since I cannot determine your prior experiance or skill level/training they are completely necessary.
Not always, sometimes they short internally, or just dry out from the heat of nearby componets.
Besides, I only mentioned electrolytics as part of my "3 question tech test" as they hold up to 165Vdc in this unit when the bleeders are open (as they often are) and can pose a bit of a hazard, even when the set is off and disconnected.
The *most* likely causes of thermal shutdown are the Vertical, Horizontal, Switching regulator and convergence circuits. They run the hottest and are likely to have ring breaks at their pins. As they cycle through hot and cool conditions (as the set is left on and off) the solder will break free eventually. Interruptions in feedback signals from these parts induce shutdown (to protect the CRT's, or keep the set from emitting X-rays). Solder them first.
Assuming that you have soldered all the connections that seem suspect and the problem presists.
Spray the above mentioned componets with a circuit chiller (freeze spray) one at a time, and try powering up the unit. The componet that allows the set to come on when it's cold is going to be the one to change.
I have almost never seen a power transformer cause the problem that you are describing (other than the Flyback transformer). Usually the cause of this is a failing semiconductor device or a shutdown triggered by a problem elsewhere (Remember, there are 15 or so of them), and as I described above, that's where things get tricky.
got the same problem with tv on and off for 10 to 15 min got any pictures on hort/ vert/switch reg &con circuits?