Calibrator
Theory of Operation
21
Power Supplies
AC line voltage is applied through a line filter to a power module in the rear
panel. The module switches to accomodate four line voltages. The outputs of the
power module are attached directly to the primaries of the mains transformer.
The safety ground wire is attached from the power module to the rear panel.
Major internal grounds are SCOM, which is attached to OUTPUT LO and the
guard shell, ICOM, which is the internal ground for the current function, and
GCOM, which is the outguard common and is attached to earth ground.
Outguard Supplies
All the transformer connections for the outguard supplies come through one
bundle of wires connected to the motherboard with P1. A row of test points in
front of the fan lets you to connect to the raw and regulated supplies. The
outguard supplies are used only by the CPU PCA (A9) and Encoder PCA (A2).
Inguard Supplies
The inguard power supplies are provided by the Voltage PCA (A8) via the
motherboard (A3). The motherboard is connected to the mains transformer and
includes current protection devices. Filter capacitors for the high-current supply
for the Current PCA (A7) are located on the Filter PCA (A12).
The inguard SCOM referenced supplies are +15 V, -15 V, +5 V, -5 V, and
+5 RLH. The +5 V and +5 RLH supplies share the same raw supply. The +5 RLH
supply is used exclusively as a relay driver and is nominally approximately 6.3 V.
Test points for these supplies are put in a row across the top of the Voltage PCA.
The 65 V supplies are rectified and filtered on the motherboard but regulated on
the Voltage PCA (A8).
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