Identify a Morrow transformer
ard at p850ug1.demon.co.uk
Thu Jun 1 19:20:25 CDT 2006
> David Griffith wrote:
> > I have a bunch of 4-inch tall transformers with ten terminals each.
> > Looking at the front, I see terminals 1 and 2 on the left. On the right
> > are 3, 4, and 5. On this side I see:
> > MORROW'S
> > DESIGN, inc
> > MD2FD8
> > On the other side are terminals 6 through 10 arranged the same way as
> > before. On this side I see:
> > TSC
> > 529
> > I presume this transformer takes 120 volts and steps it down to 16, 8, and
> > 5 volts. But what are the other terminals for? One side for 120V input
> > and the other for 240V? If you can identify it for me and want one, I'll
> > send it to you for postage.
> > A picture is at http://www.cs.csubak.edu/~dgriffi/transformer_morrow.jpg
> A possible scenario is 2*2 terminals for dual-120V-primaries and 2*3 terminals
> for two center-tapped secondaries, although usually the 4 dual-primary
> terminals would be on the same side of the core.
Another common-ish primary winding configuration, beloved of HP amongst
others  is to have 2 primary windings. One is 120V (2 connections),
the other is 120V, tapped at 100V (3 connections). You can wire them up
to work with :
100V mains : Input to the 100V part of the winding, then the 2 120V
windings in parallel. The tapped winding acts as an autotransformer to
step up the mains to 120V for the plain winding.
120V mains : The 2 120V windings in parallel, mains across them
220V mains : 120V winding in series with the 100V part.
240V mains : The 2 120V windings in series.
 I've only really seen it in HP devices, but it must have been
standard in that I've seen a combined mains input plug/filter/voltage
selector assemnly where the last part was clearly designed for this sort
Given that configruation of primaries, which uses 5 connections, you have
5 left for the secodnaries. The obvious combination would be a simple
winding to give 8V DC (regulated down to 5V) and a centre-tapped winding
to give 16-0-16V DC (regulated down to +/- 12V)
I suppose another primary configuration could be a pair of 115V windings
(paralllel for US mains, series for European mains) with another terminal
used for an inter-winding screen.
I would start by using an ohmmeter to work out just what is connected to
what. That will tell you how many windings you have, if they're tapped,
or whatever. A terminal that connects nowhwere (assuming a good
transformer!) is a screen, most likely.
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