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Thread ID: 98358	2009-03-22 00:43:00	trying again. 12volt power supply putting out 20 volts???	Colpol (444)	PC World Chat

Post ID	Timestamp	Content	User
758379	2009-03-22 00:43:00	Hi Guys. Trying again as previous thread not well written. The transmitter for my cordless headphone stopped working. No LEDs. When you plug the transmitter in the lEDs flash once then go out. Mesured voltage from the 12 volt power supply- 20 volts. Is that what you would expect? Is the unit sensing over voltage and turning off to protect itself? Cheers Colin	Colpol (444)
758380	2009-03-22 03:55:00	Certainly sounds dodgy to me, I'd be unplugging it.	pctek (84)
758381	2009-03-22 04:20:00	depends on if power supply is AC and if its regulated or not.	tweak'e (69)
758382	2009-03-22 05:16:00	depends on if power supply is AC and if its regulated or not. Transformer input is 220 VAC 50 Hz 7W Output is 12VDC 200ma 2.4VA Dont know about regulated?	Colpol (444)
758383	2009-03-22 09:10:00	Hi Colpol You have fallen for the old power supply trick . Never measure a power supply or battery without a load . The best way to think about it is this, imagine you have a flat car battery . Out comes the voltmeter and there's at least 12 volts there . Start the car, no one's home . What's the hell is going on? The problem is the car battery was measured without a load . This is just a variation of what you have done . The correct way to measure your power pack is to test it at it's load rating of 200 ma . If my Ohm's Law and Mathematics serve me correctly this means you will need to connect a 60 ohm/2 . 5 w resistor across the output . These are cheap . Find them at Dick Smith Electronics . May have to buy a 5 w one instead . About $1 . 00 each . Now measure the voltage with the resistor across the output . My guess this will cause the output to drop to near zero . In this case your power supply is stuffed . Get a new one . Hope this helps BURNZEE	Burnzee (6950)
758384	2009-03-22 19:44:00	Hi Colpol You have fallen for the old power supply trick . Never measure a power supply or battery without a load . The best way to think about it is this, imagine you have a flat car battery . Out comes the voltmeter and there's at least 12 volts there . Start the car, no one's home . What's the hell is going on? The problem is the car battery was measured without a load . This is just a variation of what you have done . The correct way to measure your power pack is to test it at it's load rating of 200 ma . If my Ohm's Law and Mathematics serve me correctly this means you will need to connect a 60 ohm/2 . 5 w resistor across the output . These are cheap . Find them at Dick Smith Electronics . May have to buy a 5 w one instead . About $1 . 00 each . Now measure the voltage with the resistor across the output . My guess this will cause the output to drop to near zero . In this case your power supply is stuffed . Get a new one . Hope this helps BURNZEE Thanks Burnzee . What you say may explain the fact that the LEDs flash once when power applied . Will get a new PS and cross fingers . Cheers Colin	Colpol (444)
758385	2009-03-22 22:09:00	Thanks Burnzee . What you say may explain the fact that the LEDs flash once when power applied . Will get a new PS and cross fingers . Cheers Colin Actually - what he said was to TEST it and then make a decision . Diagnostics are so easy to skip and then you just toss money at the problem when it may NOT be the trouble at all . Test first - buy later if need be .	SurferJoe46 (51)
758386	2009-03-23 02:08:00	Actually - what he said was to TEST it and then make a decision . Diagnostics are so easy to skip and then you just toss money at the problem when it may NOT be the trouble at all . Test first - buy later if need be . OK- went DS to buy resistor and could not remember ohms(Uncle Al visiting) . Will have to go back . Whilst there I checked out their 12 v power supplies . The only one they had was 700 MA . Mine is a 200 MA . My question is what effect will the MA rating have . Will it stuff the whole deal .	Colpol (444)
758387	2009-03-23 09:09:00	Hi Colpol Yeah, do a test before throwing money at the problem . You just might learn something along the way . That said, if you decide to buy a new power supply then a 12 volt @ 700 ma is ok . Amps or in this case milliamps are/is an indication of the maximum current the power pack can supply . As 700 ma is greater than 200 ma then the new power supply will have no problems providing just 200 ma . Hope this helps BURNZEE	Burnzee (6950)
758388	2009-03-23 09:30:00	Hi Colpol Yeah, do a test before throwing money at the problem . You just might learn something along the way . That said, if you decide to buy a new power supply then a 12 volt @ 700 ma is ok . Amps or in this case milliamps are/is an indication of the maximum current the power pack can supply . As 700 ma is greater than 200 ma then the new power supply will have no problems providing just 200 ma . Hope this helps BURNZEE Thanks Burnzee . Now I must wait to get that resistor . Will post how I got on . Cheers Colin	Colpol (444)
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