SUPPLY Unit ZA/CAN 4772
Well I bit the bullet and started the electrical tests of the Supply Unit today. Three of the tests came from the 1st Echelon Maintenance Schedule and confirmed both dynamotors spooled up and the fan circuit remained dormant. That latter test directs the operator to further tests if the fan had activated.
A couple of initial observations were that with both the MG1A and MG2A dynamotors running, and the Supply Unit free standing on the bench, the noise they produced was noticeably less than that created by the 19-Set dynamotor, when that supply is running outside of its case. I was quite impressed about that.
There was a bit of a ‘sandy’ sound coming from the area of the input brushes of MG1A (described as the 11Volt Brushes in the circuit diagrams), so I will check them out once the front panel comes off, because they are hiding right behind it.
I then hooked up my analogue test meter to the MG1A output feed to see just how well this dynamotor was working. At 12 Volt input and under load, the output should be 300 Volts. Under no load at 12 Volts, the regulation of MG1A should not allow it to exceed 35% additional output, or a total output of 405 Volts.
When switched on, it took the meter needle about 1 second to climb from 0 to 300 Volts and another couple of seconds to reach 380 Volts. Two more seconds and the needle stopped one width away from the 400 Volt mark and held there. I am thrilled with those results as my CPP-2 Power Supply was feeding a steady 12.73 Volts DC into the Supply Unit.
Next step will be assembling my string of resistors and seeing what the output of the MG2A dynamotor is doing. In the meantime, I cannot help wondering when the last time was that these two dynamotors were active.
David
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