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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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TV shuts off if any input signal is connected.
Sharp 25R-M100 27" CRT, from 2002
Got it last week through work, from someone who broke off the antenna and tried unsuccesfully to fix it. They already had a better one anyway, so they were going to junk it. I fashioned a new coax jack from a connector and a twist tie (for the center pin) and soldered them in place. For several days it worked 100% (well, it could use a de-guassing, but its minor) Then, all of a sudden, this morning upon turning on, it made the usual noise and flash of a CRT first turning on, and then immediatly shut off again. The power strip it plugs into is shut off at night to save electricity, so there is no chance that any part was too warm or that it needed to be reset via disconnecting the power. I have found that this only happens when the antenna is plugged in (actually the coax line is from the ReplayTV, which in turn is plugged into a 12v amplified roof antenna via coax) If it is on channel "input" then it shuts off if there is a signal at the composite input. With coax and composite unplugged, I can go through all channels, I get the normal blue screen, and I can access the built in menu. Therefor there is clearly nothing wrong with its capacity to display an image. But as soon as I plug it in to an incoming signal, it shuts off. I can generally see an instant of what would be on the screen, and for that instant it looks normal. Once it has shut off, it must be unplugged for a few seconds before I can turn it on again. Once I have done that it will operate from either the front controls or the remote (assuming I unplug the signal again). I have searched the forums, and while there are several entries on spontaneous shut down, none mention that it only happens if the antenna (or cable or whatever) is plugged in. Hopefully that condition will make it much easier to narrow down the problem. Thanks |
#2
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TV shuts off if any input signal is connected.
Jacob Aziza wrote:
Sharp 25R-M100 27" CRT, from 2002 Got it last week through work, from someone who broke off the antenna and tried unsuccesfully to fix it. They already had a better one anyway, so they were going to junk it. I fashioned a new coax jack from a connector and a twist tie (for the center pin) and soldered them in place. For several days it worked 100% (well, it could use a de-guassing, but its minor) Then, all of a sudden, this morning upon turning on, it made the usual noise and flash of a CRT first turning on, and then immediatly shut off again. The power strip it plugs into is shut off at night to save electricity, so there is no chance that any part was too warm or that it needed to be reset via disconnecting the power. I have found that this only happens when the antenna is plugged in (actually the coax line is from the ReplayTV, which in turn is plugged into a 12v amplified roof antenna via coax) If it is on channel "input" then it shuts off if there is a signal at the composite input. With coax and composite unplugged, I can go through all channels, I get the normal blue screen, and I can access the built in menu. Therefor there is clearly nothing wrong with its capacity to display an image. But as soon as I plug it in to an incoming signal, it shuts off. I can generally see an instant of what would be on the screen, and for that instant it looks normal. Once it has shut off, it must be unplugged for a few seconds before I can turn it on again. Once I have done that it will operate from either the front controls or the remote (assuming I unplug the signal again). I have searched the forums, and while there are several entries on spontaneous shut down, none mention that it only happens if the antenna (or cable or whatever) is plugged in. Hopefully that condition will make it much easier to narrow down the problem. Hi... Fashioned a new coax jack from a connector and a twist tie for the center pin? Don't understand what the twist tie does, but I'm scared Start by getting ahold of a proper connector, and installing it properly. Then try it again. Take care. Ken |
#3
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TV shuts off if any input signal is connected.
the connector is a coax male-male adaptor, for connecting two cables to each other. It was built assuming that each cable would have the little wire in the middle. The TV side of it was broken off with the original connector. The twist tie (with the paper stripped off) just serves as a thin piece of metal to go in the middle. I don't think that is the problem (wouldn't make any sense.) As to installing it properly, how would you connect the coax jack except with solder? It needs to be a secure electrical connection. If I had something designed for this purpose, would it not be essentially the exact same thing, (except for a lot of money), and wouldn't it still be soldered in place? I thought of the possibility that I had shorted the coax by having a bit of solder crossed between the two, but in that case, why would the same thing happen from the RCA composite input even with the coax unplugged? The RCA jacks aren't routed through the coax, they are entirely different types of signal. Any particular reason why building the part would cause this problem but buying it wouldn't? Ken Weitzel wrote: Hi... Fashioned a new coax jack from a connector and a twist tie for the center pin? Don't understand what the twist tie does, but I'm scared Start by getting ahold of a proper connector, and installing it properly. Then try it again. Take care. Ken |
#4
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TV shuts off if any input signal is connected.
"Jacob Aziza" wrote in message ups.com... I have found that this only happens when the antenna is plugged in (actually the coax line is from the ReplayTV, which in turn is plugged into a 12v amplified roof antenna via coax) Sounds like you are grounding the set out - this is very bad and possibly dangerous. |
#5
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TV shuts off if any input signal is connected.
Could you explain what this means, what it would cause, and how I can
fix it? Why would it happen only when connected to a video source? The same exact wires plugged into my other TV set works 100%, so they are not grounded. But if it were grounded internally, it shouldn't matter if a video source is plugged in or not. Right? Homer J Simpson wrote: "Jacob Aziza" wrote in message ups.com... I have found that this only happens when the antenna is plugged in (actually the coax line is from the ReplayTV, which in turn is plugged into a 12v amplified roof antenna via coax) Sounds like you are grounding the set out - this is very bad and possibly dangerous. |
#6
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TV shuts off if any input signal is connected.
"Jacob Aziza" wrote in message oups.com... Could you explain what this means, what it would cause, and how I can fix it? It may mean that you have a live chassis (which is strange these days) and that you have bypassed the safety system built into the set, which is very dangerous. Why would it happen only when connected to a video source? Because that's when you are grounding the antenna input. The same exact wires plugged into my other TV set works 100%, so they are not grounded. But if it were grounded internally, it shouldn't matter if a video source is plugged in or not. Right? Right. Something is wrong. |
#7
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TV shuts off if any input signal is connected.
Check for voltage between the antenna port and your antenna wire with a
voltmeter. Also check between your antenna and earth for voltage and the antenna port and earth. This should give you some idea where to start looking for problems. - Mike "Homer J Simpson" wrote in message news:Rtu7h.15170$C94.1683@edtnps82... "Jacob Aziza" wrote in message oups.com... Could you explain what this means, what it would cause, and how I can fix it? It may mean that you have a live chassis (which is strange these days) and that you have bypassed the safety system built into the set, which is very dangerous. Why would it happen only when connected to a video source? Because that's when you are grounding the antenna input. The same exact wires plugged into my other TV set works 100%, so they are not grounded. But if it were grounded internally, it shouldn't matter if a video source is plugged in or not. Right? Right. Something is wrong. |
#8
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TV shuts off if any input signal is connected.
Thank you for your responce.
Should there be voltage between any of those places? When you say "earth" you mean the ground wire at the outlet, right? Michael Kennedy wrote: Check for voltage between the antenna port and your antenna wire with a voltmeter. Also check between your antenna and earth for voltage and the antenna port and earth. This should give you some idea where to start looking for problems. - Mike "Homer J Simpson" wrote in message news:Rtu7h.15170$C94.1683@edtnps82... "Jacob Aziza" wrote in message oups.com... Could you explain what this means, what it would cause, and how I can fix it? It may mean that you have a live chassis (which is strange these days) and that you have bypassed the safety system built into the set, which is very dangerous. Why would it happen only when connected to a video source? Because that's when you are grounding the antenna input. The same exact wires plugged into my other TV set works 100%, so they are not grounded. But if it were grounded internally, it shouldn't matter if a video source is plugged in or not. Right? Right. Something is wrong. |
#9
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TV shuts off if any input signal is connected.
"Jacob Aziza" wrote in message ups.com... Thank you for your responce. Should there be voltage between any of those places? When you say "earth" you mean the ground wire at the outlet, right? 'Earth' is British for 'Ground'. |
#10
Posted to sci.electronics.repair
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TV shuts off if any input signal is connected.
Jacob Aziza wrote:
Could you explain what this means, what it would cause, and how I can fix it? Why would it happen only when connected to a video source? The same exact wires plugged into my other TV set works 100%, so they are not grounded. But if it were grounded internally, it shouldn't matter if a video source is plugged in or not. Right? Homer J Simpson wrote: "Jacob Aziza" wrote in message roups.com... I have found that this only happens when the antenna is plugged in (actually the coax line is from the ReplayTV, which in turn is plugged into a 12v amplified roof antenna via coax) Sounds like you are grounding the set out - this is very bad and possibly dangerous. try this unplug your coax and turn the set on, then touch only the shield of your coax connector to the outside of the ant coax, if you see a spark or the set turns off then you indeed do have a ground loop problem...and if so check your ace plug to see if someone might have cut off the ears of the plug, meaning the wide termianl of the plug if so them look closely and replug the plug into a wall outlet making sue the wide term goes into the wide side of the outlet |
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