> Anneal - is that where you heat it up & hit it with a hammer? Or do you
> just heat it up and let it cool again? I forget now... It's been a long
> long time since I had any metalwork lessons.
Heat to cherry red, then cool very slowly, often covered in lime, IIRC,
to hold the heat in. The very slow cooling keeps the metal soft, vs
cooling quickly ( quenching ) to harden.
Adrian Vickers wrote:
> At 19:31 07/10/2001, you wrote:
>
> > > >Aluminium won't do a darn thing about 50Hz magnetic fields. You want
> > > >something like mild steel, or better still mu-metal (if you can get it at
> > > >a sensible price, or indeed, at all).
> > >
> > > Okay, that makes sense. I *should* be able to get hold of some of this
> > > "mu-metal" stuff - I know people at an electicity/electronics R&D
> > lab.... :)
> >
> >It's worth asking. Really you need to anneal it after bending it to
> >shape (bending it will affect the magnetic properties and will make it
> >less good as a sheild). But in practice if you don't bend it except at
> >the corners where you have to, it will be a lot better than nothing.
>
> Anneal - is that where you heat it up & hit it with a hammer? Or do you
> just heat it up and let it cool again? I forget now... It's been a long
> long time since I had any metalwork lessons.
>
> > >
> > > I will have a poke around with my multimeter tomorrow...
> >
> >In another post you mentioned you could easily detect the stray field
> >with a screwdriver (ouch!).
>
> Well, a screwdriver bit. It's one of those 1.5in long bits which go into a
> handle, or drill.
>
> >OK, take the loads off the transformer. Pull the power connector off the
> >mainboard, and unplug the cable to the monitor. Is there still the same
> >stray field (if so, suspect shorted turns or similar in the transformer).
>
> Yes, it's still there, albeit not quite so strongly. Still enough to induce
> a noticable vibration in my magnet-on-a-stick.
>
> >If not, then reconnect one of the loads (say the mainboard) and see what
> >the field is like now. Then try connecting the other load (monitor) on
> >its own and see what the field is like.
> >
> >If one of the loads causes a rediculous increase in the field, then check
> >the rectifiers and smoothing capacitors in that section...
>
> No, not ridiculous (at least, I don't think so), but there is a noticable
> increase when the monitor load is added.
>
> From this, can I deduce that:
>
> a) The transformer is kaput (or, at least, on its way out)
> b) There may be a borderline problem inside the monitor cabinet.
>
> I've not got around to the multimeter test yet - I need to take the
> mainboard out to access the underside, and that's not a task to be doing at
> 2:20am....
>
> --
> Cheers, Ade.
> Be where it's at, B-Racing!
> http://b-racing.co.uk
>
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Received on Mon Oct 08 2001 - 12:36:18 BST