RF amplifier
Radiofrequency Power Amplifier (RPA) — broadband, high-power amplifier that drives the MRI transmit coil. Duty-cycle-limited; produces the RF excitation pulses that tip nuclear spins. One of the high-cost service items on any clinical MRI alongside cold head, gradient amplifier (GPA), and RF coils.
Why it matters to buyers: Arcing or low transmit power = stop scanning. Failures at high duty cycle (long T2-weighted, fat-saturated, or high-SAR sequences) announce themselves audibly — sharp pop, ozone smell, or sudden sequence failure. RPA condition is part of refurb due-diligence.
Why it matters to engineers: Classed by fault codes — 30-series typically power-supply failures (more recoverable), 40-series typically final-stage failures (requires full RPA swap — no field repair). On Philips dStream systems, the RF chain architecture is different (digital broadband at the coil connector), so analog-RPA service intuition from Achieva doesn't transfer cleanly.