Wow, Mike, I didn't know about all your interesting Youtube vids. I just watched the entire video of the Automated External Defibrillator teardown - really interesting! Thanks for all the hard work! Sean On Sat, Jan 7, 2012 at 5:58 PM, Mike Harrison wrote: > On Sat, 07 Jan 2012 15:33:54 -0700, you wrote: > >>Good day to all. >> >>I was looking for some cheap mains-powered mini-USB and micro-USB >>(5V) power supplies a few months back and purchased some from >>eBay. =A0They've been sitting on the shelf until a few weeks ago. >> >>Upon going to use one of these units for the first time, something >>odd caught my eye. =A0Although the input voltage rating is 100V - 240 >>Vac, the output voltage was shown as 4.5-9.5 Vdc @ 800mA. =A0This >>seemed odd but I didn't really pay much attention to it. >> >>I ran one of the micro-USB supplies on the cute little Gabotronics >>micro-sized DSO / MSO units that I purchased a while back. =A0Seemed to >>work OK for that purpose. >> >>When I went to go play with the Gabotronics unit again, the power >>supply was dead. =A0I didn't have another unit with a micro-USB plug on >>it, so I opened the unit up with an eye towards fixing it. >> >>But - I'm not going to bother. >> >>This thing is total piece of excrement. >> >>One each power and small-signal transistors in the front end - and NO >>feedback voltage regulation (!!). =A0It really looks as if this thing >>was designed to supply about 4.5V with 100Vac at the input, rising to >>about 5V with 120Vac input and getting all the way to about 9.5V with >>240Vac input. >> >>In other words, its a fixed ratio power supply with absolutely NO >>regulation whatsoever. >> >>Failure was input fusible resistor open and power transistor >>shorted. =A0Didn't even bother to see if the small-signal transistor is O= K. >> >>I'll use these things as a source of micro and mini USB power cables >>but I'm not going to trust the power supplies to power anything that >>I want to keep. >> >>Just thought that I'd put the word out to keep an eye out for these >>things. =A0I can see someone who lives in a 230Vac part of the world >>being bit rather badly by the 9V or so output when they were >>expecting 5V. =A0Talk about "Ouch!" !! >> >>dwayne > > > Sounds similar to this one I took apart recently, except mine had only ON= E transistor! > > http://www.youtube.com/watch?v=3DT88ej64aXUM > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .