OpEL > A&D Board > Transformer test

Testing The green lab kit transformer

To check the windings:.

Measure Resistance    Aproximate Value   
From Pin 1 to Pin 2 36 Ohms
From Pin 1 to Pin 3 72 Ohms
From Pin 1 to Pin 4 Very high
From Pin 1 to Pin 6 Very high
From Pin 4 to Pin 5 75 Ohms
From Pin 6 to Pin 7 72 Ohms
  • If the tests above are good, Apply 10Vpp at 1kHz to Pin 1 with Pin 3 connected to the generator ground
    • Measure V from Pin 2 to Pin 3 using the same ground point (should be about 5Vpp)
    • Measure V from Pin 4 to Pin 5 (should be about 9.8Vpp)
    • Measure V from Pin 6 to Pin 7 (should be about 9.8Vpp)
  • NOTE: A bad cable can make a circuit act as if the transformer has failed.
    If you are having strange problems with your transformer...
    • check your cables to make sure that they all have good grounds
    • The scope Ch1, CH2, and function generator all have a common ground.
      The common ground can hide a bad cable ground because the other cables provide a ground path.
      The ground connection fails when you go through a transformer because the primary and secondary windings are isolated from each other.
      If you seem to have a signal on the secondary until you connect all of the cable grounds, one of the cables is bad.
    • The ohm meter can check for a broken ground in a cable.
    • If the bad connection is intermittent, it can be very difficult to find.






This page updated February 3, 2014