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ben1990

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  1. Hey guys, bought a 12v 1 amp automatic sealed lead acid battery charger yesterday for a project, cut mains plug off and alligator clips off and hardwired it into a project, left in original case. It worked fine for about 10 minutes and a loud buzzing started. I unplugged it and it stopped. Double checked wiring and polarity, all fine. I disconnected the charger from the batteries and it stops, although a faint hum is still audible from the transformer. I pulled it apart to double check the noise was coming from the transformer, and it is. its a typical laminated iron core 240v primary to a centre tapped secondary, disconnected the transformer from the board, and open-circuit voltage is 42v across the whole secondary and 21v between each end and the centre tap. Anyone had a transformer act like this? Should I solder the leads back to the board and just let it run to see if it goes away? Not real keen on an electrical fire haha. Any help appreciated. Note: warranty is probably out of the question seeing as I cut the mains plug off and the alligator clips. Was only $20 bucks but still, would like to not have to resort to another charger.
  2. Hey guys I have a 13.8 volt, 12 amp power supply in my room running a car stereo hooked to the PC, The fan that was in it failed (50mm) so I swapped it for a new one and it is much noisier than the old one, its still a 50mm, but is a little thicker than the old one and seems to move more air. A good thing yeah, knowing that it wont overheat......but the noise is really annoying..... The stereo only draws around 4 amps at peak volume, if that......so was thinking about a thermal fan controller, thermistor on the heatsink controlling a transistor switch.....adjustable of course.....was just gonna put a switch on the fan but i am worried about frying it of course......fitting the larger fan needed the removal of one heatsink fin already Any ideas?
  3. yeah the amp has low level inputs available, as we are using the hi level inputs from the factory head unit. We can just feed it in there
  4. hey guys, a friend just bought a BMW, we just fitted 4 new speakers and an amplifier, but for fun he wants a circuit that will play a recording of the word Wilkommen (Welcome in German) through the system when the ignition is turned on. I guess i need to rig up some sort of circuit that will take a 12v positive trigger and have it trigger an MP3 player to play the file ONCE, but that will take too much time for the player to load and etc. so if anyone can suggest something that will take a 12v trigger and power supply, allow recording and playback of audio at line level and be able to do it within 3 seconds of receiving the trigger it would be very helpful, thanks.
  5. Hey guys I'm building a portable music desk which runs off of an optima yellow top car battery. Problem is my mixer has a 12v AC input from a plugpack transformer (wall-wart to the US). I was wondering if running 12v dc straight into it would be fine. The desk has 2 pioneer cd/tuner car stereos, the small mixer and a kenwood 2x60w amplifier for output. Its a great little setup once its finished but yeah this is the only hold up.
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