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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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Osvaldo de Banfield's Avatar
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Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
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.
Osvaldo F. Zappacosta. Electronic Engineer UTN FRA from 2001.
Argentine Ham Radio LW1DSE since 1987.
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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
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Location: Palatiw, Pasig City
secondary phasing is important, if you get it wrong, there will be oscillation, you get it right and you get the nfb working is a 50-50 chance you will get it right the first time....
planet10 needs your help: Let's help Ruth and Dave...[B
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