240 Power Management Unit Fault Finding TB8100 Service Manual© Tait Electronics Limited September 200613.9 AC ModuleImportant When removing plug-in cards, we strongly recommendthat you use the TB8100 card remover1 , as shown inFigure 15.1 on page 263. A flat-blade screwdriver mayreach too far through the slot and damage the componentsor tracks on the card.These checks will verify the correct operation of the AC converter. Thetest procedures require you to power-up the AC converter on approximately30VDC. Running the AC converter on DC is made possible by carryingout the following modifications to its standard set-up:■ Replacing the standard PFC control card with a spare card which hasbeen modified as described in “Modifying the PFC Control Card” onpage 246.■ Connecting two variable voltage DC power supplies as shown inFigure 13.11 on page 243. Note that the control power supply isconnected via back-power protection diodes and a high power resistor.The variable voltage DC power supplies must be able to provide the correctinput voltages for the AC converter under test. The current capability ofthese power supplies will decide how much load you can connect to theconverter. Testing at light loads will be enough to verify if the converter isworking. Variable power supplies with a 3A capability would be sufficient.Caution Even though the AC converter is running on a lowDC voltage, there is still 400VDC present on theboard.If you have been directed to this section from “Initial Checks” and the PMUis still fully assembled, go to Task 1. This allows you to check the operationof the 400VDC bus without disassembling the entire PMU (you only needto remove the top cover). If you have already checked the DC converterand the PMU is disassembled, go to Task 2.Warning!! The AC power on/off switch does not isolate thePMU from the mains. It breaks only the phase cir-cuit, not the neutral.1. The card remover is included in the TBA0ST2 tool kit, which is availablefrom your nearest Tait Dealer or Customer Service Organisation. It is alsoavailable separately as part number 220-02034-01.
