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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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My son noticed that the battery area of our TV remote was quite hot. I
immediately removed the batteries, both were almost too hot to hold onto. Sorry, I didn't check to see if the batteries were installed with the polarities correct. They had gotten so hot that the plastic surrounding the negative terminal that connects to the PCB was slightly melted and deformed. A new set of batteries did not cause the remote to function. I disassembled the remote and completely cleaned it. Scraped gunk out of the holes in the remote casing with a small jewelers screwdriver followed with a toothbrush and soapy water. Cleaned the flexible plastic sheet that functions as the button pad with soapy water and toothbrush. Completely dried everything with a hair dryer. Carefully pulled on spring for neg. terminal, stretching it so it will retain a battery, reassembled and put in fresh set of batteries. All is well. What caused the batteries to get hot? |
#2
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powrwrap wrote:
My son noticed that the battery area of our TV remote was quite hot. I immediately removed the batteries, both were almost too hot to hold onto. What caused the batteries to get hot? Dunno, probably an internal short from leaking somewhere, or perhaps some object was sitting on the remote a long time?. Looks like you may have cleared it now. Anyway - please make sure that the batteries you are using in this are NOT of the rechargeable type. If they are, that would explain the high temperatures and deformed terminal. -- Adrian C |
#3
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On Dec 11, 11:29*am, powrwrap wrote:
My son noticed that the battery area of our TV remote was quite hot. I immediately removed the batteries, both were almost too hot to hold onto. Sorry, I didn't check to see if the batteries were installed with the polarities correct. They had gotten so hot that the plastic surrounding the negative terminal that connects to the PCB was slightly melted and deformed. A new set of batteries did not cause the remote to function. I disassembled the remote and completely cleaned it. Scraped gunk out of the holes in the remote casing with a small jewelers screwdriver followed with a toothbrush and soapy water. Cleaned the flexible plastic sheet that functions as the button pad with soapy water and toothbrush. Completely dried everything with a hair dryer. Carefully pulled on spring for neg. terminal, stretching it so it will retain a battery, reassembled and put in fresh set of batteries. All is well. What caused the batteries to get hot? If the batteries were making poor contact with the negative spring, that in itself could have caused localized heating right at the spring. |
#4
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On Dec 11, 1:17*pm, "hr(bob) "
wrote: On Dec 11, 11:29*am, powrwrap wrote: If the batteries were making poor contact with the negative spring, that in itself could have caused localized heating right at the spring. OK that's plausible. I'll stretch the springs out even more. |
#5
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On Thu, 11 Dec 2008 13:33:52 -0800 (PST), powrwrap
wrote: On Dec 11, 1:17*pm, "hr(bob) " wrote: On Dec 11, 11:29*am, powrwrap wrote: If the batteries were making poor contact with the negative spring, that in itself could have caused localized heating right at the spring. OK that's plausible. I'll stretch the springs out even more. I doubt that is it. Remotes draw very little current for very short periods of time. I poor connection would cause eratic behavior, but not a lot of heat. I suspect the batteries were somehow shorted thereby causing the current to be only limited by the battery's internal resistance. That would heat the batteries. |
#6
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#7
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powrwrap wrote:
My son noticed that the battery area of our TV remote was quite hot. I immediately removed the batteries, both were almost too hot to hold onto. Sorry, I didn't check to see if the batteries were installed with the polarities correct. They had gotten so hot that the plastic surrounding the negative terminal that connects to the PCB was slightly melted and deformed. A new set of batteries did not cause the remote to function. I disassembled the remote and completely cleaned it. Scraped gunk out of the holes in the remote casing with a small jewelers screwdriver followed with a toothbrush and soapy water. Cleaned the flexible plastic sheet that functions as the button pad with soapy water and toothbrush. Completely dried everything with a hair dryer. Carefully pulled on spring for neg. terminal, stretching it so it will retain a battery, reassembled and put in fresh set of batteries. All is well. What caused the batteries to get hot? The resistance of the poor connections. |
#8
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My son noticed that the battery area of our TV remote was quite hot. I
immediately removed the batteries, both were almost too hot to hold onto. Sorry, I didn't check to see if the batteries were installed with the polarities correct. They had gotten so hot that the plastic surrounding the negative terminal that connects to the PCB was slightly melted and deformed. A new set of batteries did not cause the remote to function. I disassembled the remote and completely cleaned it. Scraped gunk out of the holes in the remote casing with a small jewelers screwdriver followed with a toothbrush and soapy water. Cleaned the flexible plastic sheet that functions as the button pad with soapy water and toothbrush. Completely dried everything with a hair dryer. Carefully pulled on spring for neg. terminal, stretching it so it will retain a battery, reassembled and put in fresh set of batteries. All is well. What caused the batteries to get hot? The resistance of the poor connections. The connection resistance would be an issue - it was probably the local site-of-generation of the heat which started to melt the plastic. However, I think it's a secondary issue, and not the only source of heat generation - the internal resistance of the batteries would also have been a generator. The real question is, why was so much current being drawn from the batteries (and released as heat)? A remote control, when working properly, is a relatively low-current device (a few tens of milliamperes, I imagine) with a relatively low duty transmission duty cycle, and it shouldn't be drawing more than an infinitesimal amount of power from the batteries when there's no button being pushed. I think there might be several reasons why this overheating might have occurred: - Batteries inserted backwards, in a remote which has a reverse-biased across-the-battery diode at the input to its electronics. The diode could act as an effective short-circuit across the batteries if they were inserted backwards. [Using such a diode, and not having a fuse or a resettable thermal current limiter in series with the battery, would seem like a Really Bad Idea.] - Some bit of metal came loose inside the case (maybe a loose connector, maybe a stray bit of wire) and short-circuited the battery connections. Or, possibly, some conductive liquid (salty broth?) was spilled onto/into the remote, and resulted in a near short circuit. - A cat sat on the remote, it started transmitting continuously, and (due to bad design or some sort of internal circuit fault) it drew so much current that it overheated. I tend to lean towards the second possibility, myself. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
#9
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Dave Platt wrote:
Or, possibly, some conductive liquid (salty broth?) was spilled onto/into the remote, and resulted in a near short circuit. There was mention of a leaking battery. Perhaps the liquid shorted over the base of the LED driver transistor and drove Amps through the thing. -- Adrian C |
#10
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On Dec 11, 3:46*pm, (Dave Platt) wrote:
The connection resistance would be an issue - it was probably the local site-of-generation of the heat which started to melt the plastic. *However, I think it's a secondary issue, and not the only source of heat generation - the internal resistance of the batteries would also have been a generator. The real question is, why was so much current being drawn from the batteries (and released as heat)? *A remote control, when working properly, is a relatively low-current device (a few tens of milliamperes, I imagine) with a relatively low duty transmission duty cycle, and it shouldn't be drawing more than an infinitesimal amount of power from the batteries when there's no button being pushed. I think there might be several reasons why this overheating might have occurred: - *Batteries inserted backwards, in a remote which has a reverse-biased * *across-the-battery diode at the input to its electronics. *The * *diode could act as an effective short-circuit across the batteries * *if they were inserted backwards. *[Using such a diode, and not * *having a fuse or a resettable thermal current limiter in series * *with the battery, would seem like a Really Bad Idea.] - *Some bit of metal came loose inside the case (maybe a loose * *connector, maybe a stray bit of wire) and short-circuited the * *battery connections. *Or, possibly, some conductive liquid (salty * *broth?) was spilled onto/into the remote, and resulted in a near * *short circuit. - *A cat sat on the remote, it started transmitting continuously, and * *(due to bad design or some sort of internal circuit fault) it drew so * *much current that it overheated. I tend to lean towards the second possibility, myself. * No cat, and no evidence of anything spilled on the remote. I do know that the springs on the negative battery terminals had been compressed over the years and the batteries were not snug in the compartment. How about the battery was loosely set in the battery drawer AND the remote was wedged between the sofa cushions constantly pressing down on some buttons. It's been like that overnight. Then my son comes along, pulls the remote out from the cushions and notices it is hot. (?) I'll ask him if the remote was wedged in the sofa when he gets home from school. |
#11
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On Dec 12, 8:40*am, powrwrap wrote:
On Dec 11, 3:46*pm, (Dave Platt) wrote: The connection resistance would be an issue - it was probably the local site-of-generation of the heat which started to melt the plastic. *However, I think it's a secondary issue, and not the only source of heat generation - the internal resistance of the batteries would also have been a generator. The real question is, why was so much current being drawn from the batteries (and released as heat)? *A remote control, when working properly, is a relatively low-current device (a few tens of milliamperes, I imagine) with a relatively low duty transmission duty cycle, and it shouldn't be drawing more than an infinitesimal amount of power from the batteries when there's no button being pushed. I think there might be several reasons why this overheating might have occurred: - *Batteries inserted backwards, in a remote which has a reverse-biased * *across-the-battery diode at the input to its electronics. *The * *diode could act as an effective short-circuit across the batteries * *if they were inserted backwards. *[Using such a diode, and not * *having a fuse or a resettable thermal current limiter in series * *with the battery, would seem like a Really Bad Idea.] - *Some bit of metal came loose inside the case (maybe a loose * *connector, maybe a stray bit of wire) and short-circuited the * *battery connections. *Or, possibly, some conductive liquid (salty * *broth?) was spilled onto/into the remote, and resulted in a near * *short circuit. - *A cat sat on the remote, it started transmitting continuously, and * *(due to bad design or some sort of internal circuit fault) it drew so * *much current that it overheated. I tend to lean towards the second possibility, myself. * No cat, and no evidence of anything spilled on the remote. I do know that the springs on the negative battery terminals had been compressed over the years and the batteries were not snug in the compartment. How about the battery was loosely set in the battery drawer AND the remote was wedged between the sofa cushions constantly pressing down on some buttons. It's been like that overnight. Then my son comes along, pulls the remote out from the cushions and notices it is hot. (?) I'll ask him if the remote was wedged in the sofa when he gets home from school. Have had this sort of thing happen twice over the years...the cause was the same both times: Child who could not keep his fingers out of anything with moving parts; batteries removed and re-inserted more or less continuously for hours on end. Until one of the cells was inserted backwards. Remote survived in one case, did not survive in the other. This is not conjecture...child is now an adult and confessed in detail after returning from a deployment cruise. |
#12
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It happened again last night. I watched the 6 p.m. news, shut the TV
off and put the remote on the end table. My entire family went out Christmas shopping. At about 8:30 my son picked up the remote to turn on the TV and it was hot. The batteries were extremely hot. The negative terminal was melted more than the original episode. Very strange. Obviously the thing is toast. Am now shopping for a new remote. Probably will get a universal. |
#13
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#14
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On Dec 11, 1:33*pm, Meat Plow wrote:
What caused the batteries to get hot? The battery Fairy? * Sorry I find this a bit hard to believe based upon my knowledge of built in saftey by design and my three and a half decades in the industry. Yeah, I've got nothing better to do than make up stories. Would you like me to post a photo of the melted plastic section that houses the negative terminal spring? |
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