what is a dampening resistor?

Answer 1

It is a resistor, placed in a circuit to prevent or dampen spurious oscillations. Sometimes the oscillations are necessary, as in a flyback power supply, but they can get out-of-hand, so the dampening resistor helps to keep the oscillations in a normal range. For example, if the flyback circuit is designed for 100 kHz and due to some load condition 500 kHz oscillations startup (unwanted), a damper resistor (in a damper circuit) will keep the 500 kHz oscillations to a minimum.

Any time you don't want unecessary oscillations, you use a dampening resistor.

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