Identify a Morrow transformer

[Tony Duell]

> 
> 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 [1] 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.

[1] 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 
of transformer.

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.



-tony