So, Tony, is there an orderly an reliable way to get these wall-warts open? I
seem to break about half the ones I want to fix. I've seen quite a few with
those fusible links in series with the windings, but the main problem, aside
from getting the right replacements, is getting the wall-wart opened and
resealed (often possible with MEK or such) such that it still looks
presentable.
Dick
----- Original Message -----
From: "Tony Duell" <ard_at_p850ug1.demon.co.uk>
To: <classiccmp_at_classiccmp.org>
Sent: Saturday, January 19, 2002 7:01 PM
Subject: Re: Kinda OT but that what's true HW hacker do in a pinch.
> >
> >
> > > Ouch! What ever happened to user-replacable fuses to handle such
problems?
> >
> > Yes *there is* SMD 500mA fuse and zener diode but that is AFTER that
> > darned ceramic capacitor. That why wall wart died and capacitor
>
> Brilliant!. This reminds me of a number of other safety features (and
> also self-diagnostic features) that fail to work when a fairly common
> problem occurs....
>
> > > Many transformers have thermal fuses designed to open the primary
circuit
> > > under such conditions. If you can open up the PSU box, you may find a
> > > replacable (with soldering iron and pliers) thermal fuse on top of the
> > > transformer, or stuck under the tape covering the windings.
> >
> > How diffcult to find this thermal fuse? This wart is hard to get
>
> That depends on the transformer. Sometimes it's an external thermal fuse
> on top of the tape over the windings (looks like a small metal cylinder,
> or sometimes a ceramic block). Sometimes it's under the very top layer of
> tape. Sometimes it's under the windings, but can be pulled out from one
> end. Sometimes you'd have to unwind the transformer to get to it :-(
>
> And sometimes the primary is designed to be the thermal fuse. If it
> overheats, the insulation melts, you get shorted turns, and it either
> melts the wire or blows the current-operated fuse. Apparently the former
> (wire that's designed to melt after the insulation has melted) actually
> meets most safety approvals, and it's the intended failure mode of most
> cheap wall-warts over here. Is it any wonder I can't stand the darn things?
>
> > voltages w/ 16VAC. Most I see are 9, 12 and nothing of to find. I
> > had to make do w/ 12VAC for short term.
>
> I'd probably buy a transformer (15V is common over here, and would be
> near enough, I think). Mount it in an earthed metal box with primary and
> secondary fuses, and a thermal fuse in series with the primary. Oh, and
> add decent mains connectors. It may not be as neat as the original, but
> IMHO it's safer and easier to repair. That's what I normally do for
> missing/defective wall warts. Or sometimes I do it even if I have the
> right wall-wart, if I don't think the latter meets _my_ safety standards.
>
> -tony
>
>
Received on Sat Jan 19 2002 - 21:02:19 GMT