Power Supplies - Agilent Technologies 5975C TAD VL MSD Troubleshooting And Maintenance Manual

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Electronics

Power Supplies

Low voltage (AC-DC) power supply
The low voltage power supply is mounted next to the toroid transformer in the
electronics module. A universal input power supply, it converts AC line voltage
into the DC voltages used by the rest of the electronics. The power supply
generates the following DC voltages:
• +24 V (nominal)
• +15 V (nominal)
• –15 V (nominal)
• +5 V (nominal)
High voltage (HED) power supply
The high voltage power supply provides the –10,000 volts DC for the high
energy dynode (HED) in the detector for the EI MSD. The EI/PCI/NCI MSD
(G3174A) requires a bipolar power supply that can also provide +10,000 volts
for NCI operation. The HED power supply also provides 600 VDC for the
detector focus lens. Due to the high impedance of this circuit, measuring the
detector focus voltage with a handheld voltmeter will give a typical reading of
90 to 100 volts where the polarity matches that of the HED voltage.
Toroid transformer
The toroid transformer is mounted next to the AC board. It provides 24 VAC
for the mass filter and source heater circuits. The input wires take 120 VAC or
200 to 260 VAC from the AC board. The AC board samples the line voltage and
uses a relay to appropriately strap the toroid primary. The output wires
connect to the main board.
224 5975 Series MSD Troubleshooting and Maintenance Manual