TB8100 Service Manual Power Management Unit Card and Board Replacement 259© Tait Electronics Limited September 200615 Power Management Unit Card andBoard ReplacementThis chapter provides information on how to remove and replace the plug-in cards and auxiliary power supply board.15.1 Safety Precautions15.1.1 Personal SafetyWarning!! The PMU contains voltages that may be lethal.Refer to the ratings label on the rear of themodule.Disconnect the mains IEC connector and wait for five minutes forthe internal voltages to self-discharge before dismantling. The ACpower on/off switch does not isolate the PMU from the mains. Itbreaks only the phase circuit, not the neutral. The DC power on/off switch disables only the control circuitry. The DC input is stillconnected to the power circuitry.Warning!! These switches do not totally isolate the internalcircuitry of the PMU from the AC or DC powersupplies. You must disconnect the AC and DCsupplies from the PMU before dismantling orcarrying out any maintenance.The PMU should be serviced only by qualified technicians. All servicingshould be carried out only when the PMU is powered through a mainsisolating transformer of sufficient rating. We strongly recommend thatthe mains power to the whole of the repair and test area is supplied via anearth leakage circuit breaker.Caution The magnetics and power devices attached to theheatsink in the PMU get hot when they are operat-ing. Take care when working on a PMU that hasbeen in recent use.Caution The PMU can weigh up to 6.4kg (14.1lb). Take carewhen handling the PMU to avoid personal injury.
