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Electric shocks (was: 100V appliance on 110v power supply)
When I said "I've got a Japanese Akai S1000 sampler", I actually meant "I'm
selling a Japanese Akai S1000 sampler for someone else". As a result, I didn't know much about the unit and its condition. But I asked the owner what she used to do with regards to power supply and she gave me the transformer that she had been running it off for the past 7 years or so. Surprise surprise - it's a 240V to 115V transformer, and she said the Akai always worked fine despite being labelled 100V. In other words, she'd been using an incorrect transformer for years, but it worked anyway. A buyer emailed me today from eBay asking if the screen was still bright or if it had gone dim with age, so I plugged in the sampler using aforementioned 115V transformer and promptly got an electric shock from an area on the sampler's case where a bit of the paint had been scratched off, leaving bare metal. It is worth bearing in mind that I was barefoot and standing on a concrete garage floor, but nevertheless, this shouldn't happen. I plugged it in again and the same thing happened. However, when turned on, the sampler worked fine - it just gave me a shock whenever I touched the case (a sizeable electric shock, not like static). The owner said that she'd never experienced this before despite using the sampler with the same transformer on a UK mains supply. One thing I noticed about the unit was that it used a 2-pin power lead with apparently no earth. As in, the socket on the machine only had 2 pins, so there was no option to use an earthed cable (even though the transformer had earthed sockets). What's the deal with this? Can anything be done? Obviously I can't sell a unit on eBay in Very Good Condition if it shocks you when you plug it in, even if it works fine otherwise. Is my only option to sell it as-seen with a buyer warning? Thanks, -- tj hertz |
#2
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"TJ Hertz" wrote ...
When I said "I've got a Japanese Akai S1000 sampler", I actually meant "I'm selling a Japanese Akai S1000 sampler for someone else". As a result, I didn't know much about the unit and its condition. But I asked the owner what she used to do with regards to power supply and she gave me the transformer that she had been running it off for the past 7 years or so. Surprise surprise - it's a 240V to 115V transformer, and she said the Akai always worked fine despite being labelled 100V. In other words, she'd been using an incorrect transformer for years, but it worked anyway. Generously-designed equipment can likely take a 15% over- voltage although it may run warmer (and may reduce its expected lifespan.) But lots of modern equipment is designed on the very edge of acceptable ranges, so I wouldn't try it as a rule. A buyer emailed me today from eBay asking if the screen was still bright or if it had gone dim with age, so I plugged in the sampler using aforementioned 115V transformer and promptly got an electric shock from an area on the sampler's case where a bit of the paint had been scratched off, leaving bare metal. It is worth bearing in mind that I was barefoot and standing on a concrete garage floor, but nevertheless, this shouldn't happen. I plugged it in again and the same thing happened. However, when turned on, the sampler worked fine - it just gave me a shock whenever I touched the case (a sizeable electric shock, not like static). The owner said that she'd never experienced this before despite using the sampler with the same transformer on a UK mains supply. PLEASE DON'T do that experiment again. We would miss you if you electrocuted yourself! Seriously! There are SAFE ways of testing for this that don't put your life or limb at risk. One thing I noticed about the unit was that it used a 2-pin power lead with apparently no earth. As in, the socket on the machine only had 2 pins, so there was no option to use an earthed cable (even though the transformer had earthed sockets). What's the deal with this? Can anything be done? Obviously I can't sell a unit on eBay in Very Good Condition if it shocks you when you plug it in, even if it works fine otherwise. Is my only option to sell it as-seen with a buyer warning? Now that you know about it, and especially now that you have revealed it in public, you really have no ethical choice but to disclose it to any potential buyer. If somebody bought it and electrocuted themselves full disclosure would be your minimum defense. If it were me, I would be tempted to fit an IEC power connector on it (like the kind used for computers), with the green-wire ground securely bonded to the metal chassis. But mains wiring is not a project for amateurs. I would think that most consumer equipment service shops ("TV Repair", etc.) would be equipped for and experienced with testing and fixing this kind of problem. Ironically, it may be working just as it was designed back when it was first sold. But you can't get away without telling bidders about the hazard today IMHO. |
#3
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One thing I noticed about the unit was that it used a 2-pin power lead with apparently no earth. As in, the socket on the machine only had 2 pins, so there was no option to use an earthed cable (even though the transformer had earthed sockets). What's the deal with this? Can anything be done? Obviously I can't sell a unit on eBay in Very Good Condition if it shocks you when you plug it in, even if it works fine otherwise. Is my only option to sell it as-seen with a buyer warning? If you sell this product, even with a warning, you are opening up yourself to servere liability issues. An electric shock can be painful under the best conditions and potentially deadly under the worst conditons. It's likely that the transformer that the person you bought this from was providing isolation and hence their claim of no shocks may have valid. Beachcomber |
#4
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"Richard Crowley" wrote in message ... "TJ Hertz" wrote ... One thing I noticed about the unit was that it used a 2-pin power lead with apparently no earth. As in, the socket on the machine only had 2 pins, so there was no option to use an earthed cable (even though the transformer had earthed sockets). What's the deal with this? Can anything be done? Obviously I can't sell a unit on eBay in Very Good Condition if it shocks you when you plug it in, even if it works fine otherwise. Is my only option to sell it as-seen with a buyer warning? Someone pointed out the online manual. It has specific mention of earthing in certain regions. You might want to take a look. Maybe something there will be worth knowing. j |
#5
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Richard Crowley wrote:
"TJ Hertz" wrote ... When I said "I've got a Japanese Akai S1000 sampler", I actually meant "I'm selling a Japanese Akai S1000 sampler for someone else". As a result, I didn't know much about the unit and its condition. But I asked the owner what she used to do with regards to power supply and she gave me the transformer that she had been running it off for the past 7 years or so. Surprise surprise - it's a 240V to 115V transformer, and she said the Akai always worked fine despite being labelled 100V. In other words, she'd been using an incorrect transformer for years, but it worked anyway. Generously-designed equipment can likely take a 15% over- voltage although it may run warmer (and may reduce its expected lifespan.) But lots of modern equipment is designed on the very edge of acceptable ranges, so I wouldn't try it as a rule. A buyer emailed me today from eBay asking if the screen was still bright or if it had gone dim with age, so I plugged in the sampler using aforementioned 115V transformer and promptly got an electric shock from an area on the sampler's case where a bit of the paint had been scratched off, leaving bare metal. It is worth bearing in mind that I was barefoot and standing on a concrete garage floor, but nevertheless, this shouldn't happen. I plugged it in again and the same thing happened. However, when turned on, the sampler worked fine - it just gave me a shock whenever I touched the case (a sizeable electric shock, not like static). The owner said that she'd never experienced this before despite using the sampler with the same transformer on a UK mains supply. PLEASE DON'T do that experiment again. We would miss you if you electrocuted yourself! Seriously! There are SAFE ways of testing for this that don't put your life or limb at risk. One thing I noticed about the unit was that it used a 2-pin power lead with apparently no earth. As in, the socket on the machine only had 2 pins, so there was no option to use an earthed cable (even though the transformer had earthed sockets). What's the deal with this? Can anything be done? Obviously I can't sell a unit on eBay in Very Good Condition if it shocks you when you plug it in, even if it works fine otherwise. Is my only option to sell it as-seen with a buyer warning? Now that you know about it, and especially now that you have revealed it in public, you really have no ethical choice but to disclose it to any potential buyer. If somebody bought it and electrocuted themselves full disclosure would be your minimum defense. Yeah, I know, and that's probably what I'll do - I was just asking if there were any ways of fixing it. Obviously if the problem remains I will warn any buyer. If it were me, I would be tempted to fit an IEC power connector on it (like the kind used for computers), with the green-wire ground securely bonded to the metal chassis. But mains wiring is not a project for amateurs. I would think that most consumer equipment service shops ("TV Repair", etc.) would be equipped for and experienced with testing and fixing this kind of problem. Ironically, it may be working just as it was designed back when it was first sold. But you can't get away without telling bidders about the hazard today IMHO. I'll take it into a repair shop methinks. Thanks for the help. TJ -- tj hertz |
#6
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"TJ Hertz" wrote in message
k... When I said "I've got a Japanese Akai S1000 sampler", I actually meant "I'm selling a Japanese Akai S1000 sampler for someone else". As a result, I didn't know much about the unit and its condition. But I asked the owner what she used to do with regards to power supply and she gave me the transformer that she had been running it off for the past 7 years or so. Surprise surprise - it's a 240V to 115V transformer, and she said the Akai always worked fine despite being labelled 100V. In other words, she'd been using an incorrect transformer for years, but it worked anyway. A buyer emailed me today from eBay asking if the screen was still bright or if it had gone dim with age, so I plugged in the sampler using aforementioned 115V transformer and promptly got an electric shock from an area on the sampler's case where a bit of the paint had been scratched off, leaving bare metal. It is worth bearing in mind that I was barefoot and standing on a concrete garage floor, but nevertheless, this shouldn't happen. I plugged it in again and the same thing happened. However, when turned on, the sampler worked fine - it just gave me a shock whenever I touched the case (a sizeable electric shock, not like static). The owner said that she'd never experienced this before despite using the sampler with the same transformer on a UK mains supply. One thing I noticed about the unit was that it used a 2-pin power lead with apparently no earth. As in, the socket on the machine only had 2 pins, so there was no option to use an earthed cable (even though the transformer had earthed sockets). What's the deal with this? Can anything be done? Obviously I can't sell a unit on eBay in Very Good Condition if it shocks you when you plug it in, even if it works fine otherwise. Is my only option to sell it as-seen with a buyer warning? Thanks, -- tj hertz It appears that the original usage was 240V to ground and the transformer is an autotransformer. Using this transformer with a North American 240/120V system could put the case at 120V with respect to ground. If this unit is to be used with a transformer, it will require an isolating (2 winding) 240/120V transformer and then the case can be grounded. However, why use the transformer? Why not connect directly to the 120V outlet. It will be necessary to determine which lead is the neutral. You will need a voltmeter. If the case is at 120 or so Volts to ground- reverse the wires to the plug. Check again-you want a small or negligable voltage between case and ground. Then set up the plug and leads accordingly (replacing the cord and plug to a 3 prong (hot, neutral and ground) is the best way. If you have any doubts, a competent electrician can sort it out for you in a short time- or you warn the potential buyer that it appears that the case is tied to the neutral and you don't know which wire is neutral and leave the correction to him/her. You don't want to be responsible for avoidable injuries. -- Don Kelly remove the urine to answer |
#7
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Don Kelly wrote:
"TJ Hertz" wrote in message k... When I said "I've got a Japanese Akai S1000 sampler", I actually meant "I'm selling a Japanese Akai S1000 sampler for someone else". As a result, I didn't know much about the unit and its condition. But I asked the owner what she used to do with regards to power supply and she gave me the transformer that she had been running it off for the past 7 years or so. Surprise surprise - it's a 240V to 115V transformer, and she said the Akai always worked fine despite being labelled 100V. In other words, she'd been using an incorrect transformer for years, but it worked anyway. A buyer emailed me today from eBay asking if the screen was still bright or if it had gone dim with age, so I plugged in the sampler using aforementioned 115V transformer and promptly got an electric shock from an area on the sampler's case where a bit of the paint had been scratched off, leaving bare metal. It is worth bearing in mind that I was barefoot and standing on a concrete garage floor, but nevertheless, this shouldn't happen. I plugged it in again and the same thing happened. However, when turned on, the sampler worked fine - it just gave me a shock whenever I touched the case (a sizeable electric shock, not like static). The owner said that she'd never experienced this before despite using the sampler with the same transformer on a UK mains supply. One thing I noticed about the unit was that it used a 2-pin power lead with apparently no earth. As in, the socket on the machine only had 2 pins, so there was no option to use an earthed cable (even though the transformer had earthed sockets). What's the deal with this? Can anything be done? Obviously I can't sell a unit on eBay in Very Good Condition if it shocks you when you plug it in, even if it works fine otherwise. Is my only option to sell it as-seen with a buyer warning? Thanks, -- tj hertz It appears that the original usage was 240V to ground and the transformer is an autotransformer. Using this transformer with a North American 240/120V system could put the case at 120V with respect to ground. If this unit is to be used with a transformer, it will require an isolating (2 winding) 240/120V transformer and then the case can be grounded. However, why use the transformer? Why not connect directly to the 120V outlet. It will be necessary to determine which lead is the neutral. You will need a voltmeter. If the case is at 120 or so Volts to ground- reverse the wires to the plug. Check again-you want a small or negligable voltage between case and ground. Then set up the plug and leads accordingly (replacing the cord and plug to a 3 prong (hot, neutral and ground) is the best way. If you have any doubts, a competent electrician can sort it out for you in a short time- or you warn the potential buyer that it appears that the case is tied to the neutral and you don't know which wire is neutral and leave the correction to him/her. You don't want to be responsible for avoidable injuries. So basically, you're saying find out which way the thing should be connected in order to let the case be neutral, replace the mains end of the cable with a 3-pin plug so that it can't be connected the wrong way, and glue/fix the sampler end of the cable into the sampler so it can't be reversed (or label which way it should go)? And this would fix the electric shock problem, but still leave the unit unearthed? I'll let an electrician deal with it because I have neither a volt/multimeter nor any spare 3-pin plugs (you don't see many in the UK), but I'd like to know what's going on anyway. Thanks -- tj hertz |
#8
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"Don Kelly" wrote ...
However, why use the transformer? Why not connect directly to the 120V outlet. Are those common in England? I've never seen any. |
#9
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On Tue, 31 May 2005 18:29:35 -0700, "Richard Crowley"
wrote: "Don Kelly" wrote ... However, why use the transformer? Why not connect directly to the 120V outlet. Are those common in England? I've never seen any. On the shaving mirror in hotels G. I just would not plug good electronics into it :O , _ , | \ MKA: Steve Urbach , | )erek No JUNK in my email please , ____|_/ragonsclaw , / / / Running United Devices "Cure For Cancer" Project 24/7 Have you helped? http://www.grid.org |
#10
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Ioslation transformer must still have the secondary (the 120
volt side) connected back to the building safety ground. If not, then the appliance will 'float' - can become electrically hot. If the transformer is properly designed, then either it has such a connection OR it has a dedicated grounding wire terminal to make that necessary connection. TJ Hertz wrote: Yeah, I know, and that's probably what I'll do - I was just asking if there were any ways of fixing it. Obviously if the problem remains I will warn any buyer. ... |
#11
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"w_tom" Ioslation transformer must still have the secondary (the 120 volt side) connected back to the building safety ground. ** Making it no longer an "isolation " transformer. If not, then the appliance will 'float' - can become electrically hot. ** The appliance's AC supply wiring will float - but nothing else since it is all insulated from that wiring. If the transformer is properly designed, then either it has such a connection OR it has a dedicated grounding wire terminal to make that necessary connection. ** A step-down / isolation transformer ought to have a ground terminal on the outlet that connects to the METALWORK of the appliance via the third pin of the plug. ........... Phil |
#12
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In article , w_tom wrote:
Ioslation transformer must still have the secondary (the 120 volt side) connected back to the building safety ground. If not, then the appliance will 'float' - can become electrically hot. If the transformer is properly designed, then either it has such a connection OR it has a dedicated grounding wire terminal to make that necessary connection. No, that's the point of isolation. Because the appliance floats, it can become "hot" but the leakage current has no reference to the building ground so if you touch the hot case, no current will flow through you. Not that a safety ground isn't _still_ a good idea, mind you. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#13
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Yes, that's why in all around the world the neutral of LV distribution
transformers is earthed (so I learned in my studies) so that you get schocked and know that electricity is dangerous (no joke) AND because in a neighborhood e.g. someone would be touching a live phase and someone else another, so that both would be exposed to the line to line voltage which is 380 V in Europe (220 V in USA).However this happens only in LV, in MV, HV and EHV there's no need for a reference to ground, because the windings of the substation transformer are in delta, ungrounded.This doesn't make the voltage not dangerous, I was told some horror stories back in Kozani. -- Tzortzakakis Dimitrios major in electrical engineering, freelance electrician FH von Iraklion-Kreta, freiberuflicher Elektriker dimtzort AT otenet DOT gr Ο "Scott Dorsey" έγραψε στο μήνυμα ... In article , w_tom wrote: Ioslation transformer must still have the secondary (the 120 volt side) connected back to the building safety ground. If not, then the appliance will 'float' - can become electrically hot. If the transformer is properly designed, then either it has such a connection OR it has a dedicated grounding wire terminal to make that necessary connection. No, that's the point of isolation. Because the appliance floats, it can become "hot" but the leakage current has no reference to the building ground so if you touch the hot case, no current will flow through you. Not that a safety ground isn't _still_ a good idea, mind you. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#14
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"Dimitrios Tzortzakakis" wrote in message
... Yes, that's why in all around the world the neutral of LV distribution transformers is earthed (so I learned in my studies) so that you get schocked and know that electricity is dangerous (no joke) AND because in a neighborhood e.g. someone would be touching a live phase and someone else another, so that both would be exposed to the line to line voltage which is 380 V in Europe (220 V in USA).However this happens only in LV, in MV, HV and EHV there's no need for a reference to ground, because the windings of the substation transformer are in delta, ungrounded.This doesn't make the voltage not dangerous, I was told some horror stories back in Kozani. -- Tzortzakakis Dimitrios major in electrical engineering, freelance electrician FH von Iraklion-Kreta, freiberuflicher Elektriker dimtzort AT otenet DOT gr --------------- In LV, MV , HV and RHV. the transformer windings can be and often are in Y.- .. The most common connection is Delta Wye with the HV side in Wye with direct or impedance grounding. There are good technical and economic reasons for that. The next most common connection is probably Y-Y -delta for supplying EHV lines . Note that even at 4160V distribution the supply transformer is Y on the 4160V side. Ground faults are the most common faults on transmission lines. This means that the unfaulted phases will see overvoltages- not good. In addition, protective relaying problems are increased and arcing faults which are not detected and often undetectable can occur because of capacitive coupling. The grounding eliminates these problems as well as problems due to the line floating up and down due to atmospheric effects (thus stressing the insulation). The use of a Y system makes life a lot easier. -- Don Kelly remove the urine to answer Ο "Scott Dorsey" έγραψε στο μήνυμα ... In article , w_tom wrote: Ioslation transformer must still have the secondary (the 120 volt side) connected back to the building safety ground. If not, then the appliance will 'float' - can become electrically hot. If the transformer is properly designed, then either it has such a connection OR it has a dedicated grounding wire terminal to make that necessary connection. No, that's the point of isolation. Because the appliance floats, it can become "hot" but the leakage current has no reference to the building ground so if you touch the hot case, no current will flow through you. Not that a safety ground isn't _still_ a good idea, mind you. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#15
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Sorry, given that it was e-bay, I didn't cjheck the origin. The solution
that I suggested was for North American usage. The key in the UK case is to pitch the original transformer and get an isolation transformer (2 winding 120/240V) -- Don Kelly remove the urine to answer "Steve Urbach" wrote in message ... On Tue, 31 May 2005 18:29:35 -0700, "Richard Crowley" wrote: "Don Kelly" wrote ... However, why use the transformer? Why not connect directly to the 120V outlet. Are those common in England? I've never seen any. On the shaving mirror in hotels G. I just would not plug good electronics into it :O , _ , | \ MKA: Steve Urbach , | )erek No JUNK in my email please , ____|_/ragonsclaw , / / / Running United Devices "Cure For Cancer" Project 24/7 Have you helped? http://www.grid.org |
#16
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On Tue, 31 May 2005 14:44:52 +0000, TJ Hertz wrote:
... promptly got an electric shock from an area on the sampler's case where a bit of the paint had been scratched off, leaving bare metal. It is worth bearing in mind that I was barefoot and standing on a concrete garage floor, but nevertheless, this shouldn't happen. This is correct. Standing barefoot on a concrete garage floor while dicking around with anything plugged into mains should never happen. Good Luck - you'll need it. Rich |
#17
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On Tue, 31 May 2005 09:15:40 -0700, Richard Crowley wrote:
"TJ Hertz" wrote ... shock whenever I touched the case (a sizeable electric shock, not like static). The owner said that she'd never experienced this before despite using the sampler with the same transformer on a UK mains supply. PLEASE DON'T do that experiment again. We would miss you if you electrocuted yourself! Seriously! There are SAFE ways of testing for this that don't put your life or limb at risk. Nah - we'll just nominate him for this year's Darwin award. Cheers! Rich |
#18
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On Fri, 03 Jun 2005 15:24:55 GMT, Rich Grise wrote:
This is correct. Standing barefoot on a concrete garage floor while dicking around with anything plugged into mains should never happen. Word up. |
#19
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"Rich Grise" wrote in message
news On Tue, 31 May 2005 14:44:52 +0000, TJ Hertz wrote: ... promptly got an electric shock from an area on the sampler's case where a bit of the paint had been scratched off, leaving bare metal. It is worth bearing in mind that I was barefoot and standing on a concrete garage floor, but nevertheless, this shouldn't happen. This is correct. Standing barefoot on a concrete garage floor while dicking around with anything plugged into mains should never happen. Good Luck - you'll need it. Rich NOTE: this experience happened in the U.S.A. and other countries may differ a friend of mine had a phonograph player in his basement. the unit operated fine, but if you touched a metal part of the player, and a metal support post in the basement, you would get a mild shock (about half of what I've gotten from touching 110v mains by accident) Later on in life, I found out that if you attempt to bypass the safety feature of polarized p,ugs for non-grounded equipment, or if the electrical outlet was wired incorrectly, this happens. as you are on a foriegn system, I cannot be sure, but I'd advise to switch the live and neutral lines. and also put an earth line in there also. -- Tater President of MARS Club (NAR #660) www.mars-rocketry.com KC9ESF NAR #79654 L1 EAA #703312 remove spam spelled backwards to reply |
#20
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tater schuld wrote:
NOTE: this experience happened in the U.S.A. and other countries may differ a friend of mine had a phonograph player in his basement. the unit operated fine, but if you touched a metal part of the player, and a metal support post in the basement, you would get a mild shock (about half of what I've gotten from touching 110v mains by accident) This is because it was a hot chassis player. That is no longer acceptable in the US, but it was very popular for many years for cheap consumer electronics to operate without a power transformer and use a hot chassis. For almost any cheap table radio, record player, or TV set made before 1970 this was the case, and for a lot of TV sets well into the eighties it remained the case. Later on in life, I found out that if you attempt to bypass the safety feature of polarized p,ugs for non-grounded equipment, or if the electrical outlet was wired incorrectly, this happens. That just makes the problem worse, yes. as you are on a foriegn system, I cannot be sure, but I'd advise to switch the live and neutral lines. and also put an earth line in there also. Grounding is a good idea, but if there is chassis leakage, that is bad and it should be fixed if possible. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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