Re: 12VDC - Have I blown my KIT?!
- From: "Dave D" <dave_d@xxxxxxxxxx>
- Date: Sun, 5 Mar 2006 16:49:51 -0000
<nickrdp@xxxxxxxxx> wrote in message
news:1141325060.386890.182950@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
HELP ! :)
I have a piece of audio equipment (M-Audio 410 firewire audio
interface) that
requires 12V DC (1000mA) I bought it in the states with a US adapter
and step down convertor (240->110). Everything was working fine until I
thought I should go out
and buy a UK voltage adapter to replace the cumbersome setup of AC
adapter -> step down transformer -> US/UK plug.
I bought a '1000mA Variable Voltage AC/AC Adapter' with a 12V setting.
After plugging it in, the lights came on and then went out on the
device, andthen nothing! Is it because I bought an AC/AC adapter and
not AC/DC adapter?? Could this cause the kit to stop working?? Its
gonna be such a pain to try and return this to the store I bought it
from in the US (Im in London), any help would be seriously appreciated.
Regards,
Nick.
The device *should* have reverse polarity protection, which could be either
(1) a reverse-biased diode across the input, or (2) a diode in series with
the + rail after the power jack.
What will happen if you connect an AC adaptor? Well, in the first instance
the diode will short out the negative component of the AC supply, and allow
the positive component to pass. The shorted negative component will quickly
either damage the power supply or blow a fuse in the appliance itself,
provided the manufacturer has been thoughtful enough to add one to the
design. At that price, they damn well should. Hopefully all this will happen
before any other damage can be done.
In the second instance, the series diode will rectify the AC to rough, half
wave DC. This could explode electrolytic caps and cause the internal
regulator to malfuction, with possibly catastrophic results. The fuse may
well not fail until it is too late, if at all as there may be no overcurrent
situation until a semiconductor fries.
The only way to know for sure what the damage is, is for a tech to look
inside. You may get very lucky and it could just be an internal (probably
miniature surface mount) fuse. OTOH, it could be a write off, there's no way
to tell from the outside. If specialist SMD ICs are blown, forget about a
local tech repairing it, it will be a manufacturer/dealer repair only, and
they might consider it uneconomical to service.
Dave
.
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- 12VDC - Have I blown my KIT?!
- From: nickrdp
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