Power supply dead?

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Tue Dec 7 22:30:45 2004

> 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

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.

Received on Tue Dec 07 2004 - 22:30:45 GMT

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