A Diagnostic Neutral Beam Injector (DNBI) is operated on the TCV Tokamak since 2000. Over the years, the plasma source and the ion optical system have benefited from several upgrades, whereas the power supply system remained almost unchanged. DNBI operation is now compromised by the obsolescence of both the power components and the control infrastructure. To allow for a long-term reliable operation, a complete renew of the power supplies set is ongoing. It includes a high-speed current source rated 500A/100V/2s for the arc-discharge plasma source and a High Voltage Modulator (HVM) rated at 55kV/5A/2s (subject of a separate paper at this conference)