Second post, but it's for a different part. The casette recorder/player box that I salvaged had a transformer. I tried to figure out exactly what it did.
two input leads for 110V.
5 output leads
(1)
(2)
(3)
(4)
(5)
now I know working with AC mains is a no-no but i insulated all of the dangerous contacts before plugging it in and (carefully) checking:
the voltage between pin 1 and pin 2 was: 5.3V
between 3 and 4: 13.8V
between 4 and 5: 13.8V
between 5 and 3: 27.7V
between 4 and 2: 0V
weird, non-standard voltages between other pins (6.8, 3.2, etc. must be just the result of coupling). leads me to believe i have a center-tapped winding for +/- 13.8V and a secondary winding for 5.3V. This makes sense from a system standpoint; the 5v for logic and signal processing, the 13.8V for analog circuitry and motors.
question: i used my multimeter in VAC setting, and I believe it would thus be an RMS voltage. Since the 5.3v did not quite make sense to me; a typical diode drops at BEST only .5V so you would be left right on the 4.8V supply threshhold for most 5V digital stuff. If the 5.3V were an RMS voltage, that means the peak is a bit higher than that, allowing for the .7V or so drop that comes with rectification and allowing the output DC voltage to be closer to 5V.
do my assumptions seem sound?