For Agilent 66319D DC power supply output fluctuation issues, focus on checking these internal components:

1. Output filter electrolytic capacitors: Drying or leakage reduces filtering effect, leading to ripple and fluctuation.
2. Precision voltage reference components: Drift or damage in reference sources (e.g., zener diodes or IC references) disrupts voltage regulation.
3. Output stage power devices: Faulty MOSFETs/transistors or poor solder joints cause unstable output current/voltage.
4. Feedback loop components: Drifted resistors/capacitors in the voltage/current feedback path affect regulation accuracy.
5. PWM controller and its peripheral parts: Malfunctioning controller ICs or timing components (resistors, capacitors) lead to unstable switching, causing output波动.

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