各位大虾,小弟学电源,做TNY264电源,怎么改参考图的5V为3V?

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各位大虾,小弟刚如行电源,准备做TNY264的电源,怎么把参考图给的5V输出改成3V输出?...是不是应该改VR1取样的稳压管?十分感谢...!!