On 03/12/2013 23:18, Lobster wrote:
Roger Mills grunted in
:

On 03/12/2013 00:30, Lobster wrote:
I have a flatscreen monitor whose (separate) PSU has died and needs
replacing. It's a 12V 3A unit, and as luck would have it I happen to
have a similar one going spare from a netbook which I no longer have.

Q1: is there any reason why this putative PSU wouldn't be fit for
purpose - ie is there any other characteristic other than 12V/3A that
I need to consider here?

Q2: Assuming we've made it past Q1 - unfortunately the (LV) plug
which connects to the monitor is slightly but crucially differently
sized to the original, so it won't fit - both are standard-looking
concentric plugs (ie this sort of thing: http://tinyurl.com/mx35688)
but the central pin is evidently larger on the monitor than it was on
my netbook (though the external diameter looks the same). What are
the specs for these things - how do I work out what plug I need to
buy? I'm assuming it's possible to buy a solderable version;
otherwise everything I have here is welded together - is there a neat
way of cutting and rejoining the LV flex so I could recycle what I
have? (I wouldn't want to bodge it as I'll probably pass this monitor
on to someone else once it's repaired...)

Be very careful! If the two power supplies have different IDs, it's
for a good reason. One will be stabilised and the other won't. An

Can't say I have ever seen enough standardisation of plug specs to draw
that conclusion.

unstabilised supply will produce a much higher voltage under no load
conditions, and relies on the load to bring the voltage down to the
required level. The plugs are designed to be different in order to
make them non-interchangeable. If you use an unstabilised supply with
something which requires the supply to be stabilised, damage may
occur!

Thanks to all for the replies.

How would I know if one PSU was stabilised? There's nothing relevant
written on either of them AFAICS. The working PSU was a laptop charger -
is that likely to mean it might be stabilised and that the purpose-
supplied item for a monitor might not have been?

Its is almost guaranteed that both will be switched mode supplies (and
hence regulated / stabilised)

(a 12V 3A linear supply would be quite a hefty brick and probably weigh
as much as the laptop!)

--
Cheers,

John.

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