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Old 2nd March 2012, 03:51 PM   #1
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Default Question on push-pull OT LEads

OK, so this might be a dumb question but why does reversing the primary leads on a push pull output transformer drive an amp into parasitic oscillation? Looking at the basic transformer wiring schematic it appears be symmetrical? Is there a standard to know which lead has to go to the input side and which lead has to go to the side with negative feedback applied? thanks.
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Old 2nd March 2012, 04:46 PM   #2
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Does the amplifier have negative feedforward from any secondary of the transformer? IF any, reverting input get it to positive FB, converting the amp in an oscillator.
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Old 2nd March 2012, 07:12 PM   #3
DF96 is offline DF96  England
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This is not parasitic oscillation, but loop oscillation. Parasitic oscillation occurs within a single stage, typically the output although it could be an earlier stage. It is caused by parasitic components e.g. stray capacitance, lead inductance.
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Old 3rd March 2012, 05:40 AM   #4
AJT is offline AJT  Philippines
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secondary phasing is important, if you get it wrong, there will be oscillation, you get it right and you get the nfb working correctly.....it is a 50-50 chance you will get it right the first time....
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