The electronic assemblies are continuously evolving towards packing increased functions within diminishing volume and weight. This makes the thermal management of these devices more challenging as the heat flux severity increases. Heat pipes have been known to be an effective tool in spreading severe fluxes. In the present study, the thermal management of a microwave amplifier - Travelling Wave Tube (TWT), with heat pipe assisted heat sink has been detailed. An existing TWT with a given heat sink-fan combination was to be replaced by a higher heat dissipating TWT. A study of the various options of cooling was made. A heat pipe embedded heat sink with suitable fans was designed and developed. The cooling scheme of the proposed heat pipe heat sink was evaluated by testing and the same was used to test the device as well. Hence a systematic study has been carried out to design and develop a cooling solution with a heat pipe embedded heat sink which is within the volume and weight of the existing TWT cooling scheme despite 1.6 times increase of heat load.