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 scenario might be 2 terminals for 120V primary, 2*3 for two
center-tapped secondaries and 2 for a third secondary. Some 70s-era floppies
used 24V, so it might be targetting +5V, +/-12V and 24V.
Some suggestions if you want to go through the process:
- Assuming that being from Morrow Designs indicates it as a low-voltage
transformer (all secondaries step down). (Did Morrow Designs do
anything else?). If there is a step-up winding the following may not apply.
- Get out an ohmmeter so as to electrically associate terminals with each
other. Highest resistance is most likely the/a primary.
- Usually one can observe the gauge of wire of the windings by looking around
the edge of the coil by each terminal, or in the gap around the last wrap of
insulation, to get an indication of the relative current capacity of the
windings. Two wires to the same terminal will typically indicate a center-tap.
For a linear supply for a computer the finest wires will likely be the
primary/s, and the heaviest wires the secondary for the 5VDC, although it's
possible the winding for the 12VDC is finer than the primary(s).
- If you can identify a primary, fire it up and measure V on the other windings.
If you're not sure enough to feel like connecting it up to 120VAC, or to be somewhat
safer, inject 6VAC-or-so (from another small transformer) instead (preferably onto
the highest resistance winding or smallest gauge), measure V on the others and
calculate proportions. You don't want to inject even that low voltage
on a heavy-gauge winding as it may draw too much current. Note if you didn't
get the primary you may have a step-up situation. A fuse on the supply is a good
idea.