OT: new info on fuse

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Mon Dec 29 21:02:01 2003

>
> >> Should I get continuity between the s-shaped swigglely lines?
> > NO!. Those should be open-circuit both ways!
>
> Well, that depends on whether it's in-circuit or not. In circuit, it
> probably will show continuity both ways (with about two diode drops of
> voltage developed), or possibly less if there's an isolation

Ture enough.

However, SMPSUs are full of low-resistance components (the transformer
windings, current sense resistors (which may be < 1Ohm), etc. IMHO the
only way to reliably test components is out-of-circuit. I think I
mentioned that in another message.

> transformer between it and the mains.

I have never seen an SMPSU with a mains isolation transformer. Yes, I
have seen PSUs that start with a mains transformer (giving, say, 20V),
and then use a switching regulator to bring that down to 5V (or
whatever), but I've never seen one with a 1:1 isolating transformer
(remmeber that 200V electrolytic, there is rectified mains in that PSU).

-tony
Received on Mon Dec 29 2003 - 21:02:01 GMT