Electronics 8
Troubleshooting and Maintenance Manual 177
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 MS. 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.
Toro id tr ansf orm er
The toroid transformer is mounted next to the AC board. It provides 24 VAC
for the mass filters and source heater circuits. The input wires take 120 VAC or
200 to 260 VAC from the AC board. The line voltage switch on the top of the
electronics module straps the toroid primary. The output wires connect to the
AC board.
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