I see that a transformer seperate clearly two arrays of pins, one for primary, one for secondary. I want to ask that if I measure Ohm of two pins in one array, the result in meter is 0.L (isolate completely), is that transformer decayed ?
And in the circuit, when I put my two test probe into two pins of primary array, it says some value of voltage but that is DC voltage (about 250V for e.g), when AC measurement, the result is about nothing, just some few miliVolt ? I see strange but don't know why
I use digital meter and when two point is completely electrical isolation than it display "0.L", I always think that.
That circuit is the power supplier for computer, it is decayed, I did testing probe on the primary coil of transformer and see that. That voltage is fed from a voltage rectifier, 220VAC to 250VDC.
PSU for computer is switching mode converter. Because of using much more frequency than 50 or 60 Hz it has lower transformer than normal PSU.
Transformer in SMPS has windings with low resistance, you can't measure their resistance because is too low. More adequate is inductance measurement, it should be some mH (but exact value depend on working frequency of SMPS).