[mythtv-users] HDPVR problems - power supply again?

Stephen Worthington stephen_agent at jsw.gen.nz
Thu Aug 15 08:32:23 UTC 2019

On Wed, 14 Aug 2019 21:30:10 -0700, you wrote:

>On 8/14/19 11:19 AM, Will Dormann wrote:
>> On 8/14/19 1:23 PM, Stephen Worthington wrote:
>>> If the HDPVR is rated at 2 amps and it draws 15 amps from the PC, it
>>> can certainly burst into flames.  The PC power supply will not be in
>>> an over current situation - it can easily supply 15 amps.
>  One sort of unrelated data point - a lot of the connectors in a typical PC are 
>not fused in any way (video card, hard drives, even MB).
>  Many years ago when I was doing support, one of the computers in the lab would 
>power on.  Doing some debugging, I pulled one of the hard drives and the user 
>asked me how I know it was that hard drive.  My answer was that I could see see 
>smoke coming off its circuit board.
>  It just seems to me that there are potentially a large number of ways anything 
>powered by a computer PS could go up in smoke, so I'm not sure why one should be 
>more concerned about the HDPVR vs a hard drive or other component.

There are usually fuses on hard drives, and I would expect them on
most cards as well.  So there is no need for fuses in the power cables
or in the motherboard slots.  Fuses have to be the right size for the
device drawing the power, so it does not make sense to put a generic
fuse in a PC power cable.  The smoke you saw coming off the drive was
likely just a capacitor destroying itself.  That does not take huge
amps - just a bad capacitor and enough volts.  So it was not a high
energy event and was unlikely to cause a fire unless the capacitor or
something nearby was highly flammable.

PCs, like most electronic equipment, are designed to meet quite
sensible safety rules and appropriate fuses are part of that.  When
electronics were being invented, there used to be fires until the
correct design rules were invented and enforced.  Just like people
were being killed left and right when houses first had mains power
installed, until the correct safety rules were worked out and
enforced.  It is pretty rare now to have a fire caused by the
electronics inside any consumer device.  The most likely place for
such a fire is in the power supply, and normally there will have to
have been damage (and/or stupidly bad design) to cause it.

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