Power supply dead?

[Vintage Computer Festival]

On Wed, 8 Dec 2004, Tony Duell wrote:

> > 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.

That's what I'm saying!

> 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.

I'm pretty sure I remembered to put it on AC since I'm thinking back to
when I tested it and I can see an image of only two options, 20 and 200,
and that particular VOM only has two option ranges for AC, so I must have
had it set right.  But just to be sure, I'll check again.

> 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).

I'll do that.

-- 

Sellam Ismail                                        Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger                http://www.vintage.org

[ Old computing resources for business || Buy/Sell/Trade Vintage Computers   ]
[ and academia at www.VintageTech.com  || at http://marketplace.vintage.org  ]