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  • Author Author: phoenixcomm
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YouTube video blogger that well got it wrong!!

phoenixcomm

You should know by know that I have a pension for things that well blow up or end badly. You can alway go to the German Safty Test video for your giggles.  He now (1:52 - 2:39) draws and explains a schematic of the power supply of this silly thing. For some strange reason, he puts a transformer after a bridge rectifier. Now when I went to grade school (a long, long time ago, when we did "duck and cover")  and you found out that DC will not make a magnet. You just don't create the magnetic lines of force.  Also, NEVER put a cap between transformer windings. Below here is what he should have drawn:

He gets a big FAIL.image

image

See you soon

image  Cris H.

  • in reply to shabaz

    Yep.

    He didn't do it very well but it certainly is the standard rectify the mains, then chop the resultant DC to get your voltage.

     

    He gets several fails from me.

    1. He knew it was giving an AC voltage but never actually measured it. (It looks like half wave mains by the lamp shown later)

    2. He decided to use some enamalled wire on a mains voltage lamp and relied on that as the primary isolation to stop him getting a shock.

         Yes says he has a RCD (why he didn't want to measure between metalwork and earth) but still it isn't the point when he knows its faulty.

    3. He tried to prove it by removing the transformer rather than cutting the track to prove it. In removing the transformer he has cleared the initial fault.

    4. Using a sharp knife and cutting towards is a NO NO . In my day that was the first thing your father taught you about knives.

    5. The comments about two sets of 'secondary' windings using three parallel wires is incorrect ... these would be the primary winding.

     

    His final conclusion is that the feedback winding was in contact with the primary winding.

    I presume that the 'earth' side of this winding is the output ground, which was then elevated to a mains voltage via diode, which gives the half wave effect observed with the lamp.

     

     

    If I'm not mistaken this has a non polarised mains plug.

    image

    A quick check would have been to reverse the mains connection to see if it stayed live.

     

     

     

    This is typical of these cheaply made devices where they are relying on basic insulation of a key component.

    The exact cause was single insulation failure (the coating only) and may well have survived if the mains was only 115v.

     

    People wonder why we promote safety around Mains Voltages and this is another very good example.

     

    Cheers

    Mark

  • Aren't Y capacitors exactly for this application? Filtering between primary and secondary.

  • Ouch - that multimeter burning video is scary.

    Ordinarily I'd agree, a lot of vloggers are pretty bad, Big Clive is usually very good though. He rushed through the description a bit, but basically he was describing an AC-DC converter (i.e. something like this block diagram), not a linear supply. It was easy to miss though, it was just very quickly sketched just as a box so it was a bit unclear.

    I've not seen the entire video but looking forward to it - curious what the end fault was.