Out on the floor, the press is screaming along at 600 fpm, and the curing window is measured in milliseconds. If the lamp’s spectral output drifts or the arc stability falls apart, you don’t get cross-linking—you get tack. That’s when you learn what the power supply and ballast are really there for. What matters, technically We match the ballast to the lamp’s mercury vapor load and how the electrodes behave thermally, so arc current stays stable even when the load jumps around. Then we tune the output to the photoinitiator: 365 nm for deep through-cure, 385 nm for pigmented flexo, 405 nm for thin-film surface cure. Peak irradiance is held at the reflector focal plane, and energy density stays above the ink’s threshold. The ballast also manages lamp warm-up, keeps electrode sputtering in check, and prevents spectral output from collapsing as the lamp ages. When the power supply is matched, you get repeatable mJ/cm² on the web—no guesswork. Why it works in UV offset, flexo, and screen In UV offset, flexo, and screen, the power supply and ballast hold the lamp steady so the press can run faster without undercuring. You see fewer rejects from surface tack, better adhesion, and a cure that stays consistent across the web. Energy use drops because the ballast doesn’t over-drive the lamp, and lamp life stretches out because the electrodes aren’t hammered at ignition and during the run. The payoff is uptime you can bank on, cycle after cycle. Things to keep straight Match the ballast to the lamp type, length, and arc voltage—mismatch that, and the wavelength shifts while lamp end-of-life comes on faster. Double-check connector compatibility, line voltage, and EMI/EMC constraints at the cabinet. Expect an ozone-free design to keep operators protected, but still verify ventilation and lamp housing clearance so reflector temperatures stay within spec.