R&S ZVA Repairs
1177.5333.02 3.25 E-11
Motherboard
The motherboard supplies power to the boards and connects them to the control and data buses. A
number of RF connections are also routed via the motherboard.
As well as straight connections, a number of circuits are accommodated on the motherboard:
Motherboard controller (MBCON)
28 V supply
Preamplifier for the DC measurement inputs
Supply voltage fuses
Rear panel interfaces
Fan control
The MBCON unit acts as an FSU bus-slave:
to drive the LEDs (instrument front-panel)
to drive the fan in five stages
for two temperature sensors on the motherboard
for an SPI-EEPROM on the motherboard
Furthermore, the software can detect which device (ZVA8 or ZVA24) is present using the MBCON.
In addition to the voltages delivered by the power supply, +28 V is produced from +12 V on the
motherboard by means of a boosting switching regulator. This voltage is required to operate the OCXO
on the reference board when option B4 is fitted.
Each board has its own fuses for the supply voltages. These fuses are soldered into position on the
board.
All external supply voltages (USB etc.) are protected to prevent shorts.
To Next Page
Loading...
