Before plugging in an old transformer, give it a thorough mechanical
inspection. Look at the diagram at:
Make sure the cord is not frayed or cracked. Make sure there is no burned
insulation smell. Open the case by removing the knobs, removing the top
metal label plate, removing the large screws under the label plate, and
removing the top part of the Bakelite case. Inspect for any signs of
burning or scorching on the transformer. Inspect the four moving contact
arms and make sure the carbon rollers that rub on the transformer winding
are intact and rotate freely. Trace the wires per the wiring diagram and
make sure none of the wires are disconnected. If all is well, reassemble
Plug it in. Observe that the green pilot light comes on. Use a voltmeter
to measure the output at A to U, B to U, C to U and D to U as you vary each
control knob. Observe that the voltage varies smoothly without
interruptions over the range specified on the label plate. If all is OK,
turn a control to maximum, and use a screw driver to make a short circuit
from that control's output post to the U post; observe that the circuit
breaker opens within a couple seconds and the red "short" light comes on.
DO NOT apply the short for more than a few seconds if the breaker does not
If it passes all of the above the transformer should be OK, but use it under
adult supervision for the first few hours to make sure that it does not
overheat, emit smoke, or unusual odors.
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.