Power supply dead?

[Tony Duell]

> 
> 
> I've got one of them TI Silent 700 Model 703 portable data terminals.  The
> external power supply that comes with it is 20VAC.  It's got three
> conductors on the connector.  I can't get any voltage out of it.  Is it
> dead?
> 
> Or is it that it needs to sense a loop or something across all pins before
> it starts emitting juice?  Not likely, I'm sure, but I thought I'd ask

I would eb very suprised.... An AC-output PSU is most likely just a 
transformer.

At the risk of 'teaching grandma to suck eggs', cna I just check that 
you're using the AC range on your multimeter (VOM, whatever you call it)? 
If you're using a DC range, it will most likely read zero.

Also, with the unit unplugged from the mains, can you measure the 
resistance betweenn the pins on the output plug (I would expect at least 
2 of these to show a low resistance between them [1]) and between the 
live and neutral pins of the mains plug (again, a finite resistance due 
to the transformer primary winding).

[1] 3 pins suggests either the 3 connections of a centre-tapped secondary 
winding, or a plain winding between 2 of the pins and mains earth ground 
on the thrid. FWIW, some HP printer power bricks have a 4 pin output 
connector, the 4 pins being mains earth and the 3 terminals of a 
centre-tapped secondary).

> before I start tearing this apart to see if it has an internal fuse.

-tony