R&S ZVA8, Service Manual

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Repairs R&S ZVA
1177.5333.02 3.24 E-11
Front unit
The front unit comprises a mounting plate on which the LCD, the flexible switch board and key pad, and
the tachogenerator are accommodated.
The front module controller is mounted in the controller tray in the instrument frame.
LC display
All results and setting information the user requires is displayed on the colour LCD.
The resolution of the LCD is 800 x 600 pixels (SVGA).
The display has an integral cold-cathode tube to provide illumination. The high voltage that is required is
provided by a dedicated DC/AC converter. The converter is mounted on the mounting plate next to the
display and connected to both the display and the controller board via a cable.
Keyboard
The keyboard comprises a flexible switch board and a key pad. They make contact whenever a rubber key
is pressed. The two LEDs for the status display associated with the Standby/On key (yellow for
standby/green for on) are also accommodated on the key pad.
Key detection and LED control are performed via a foil cable connection on the controller board. They are
controlled by means of a matrix method implemented by a special microprocessor on the controller board;
the two LEDs are controlled accordingly. When the instrument is turned off at the mains switch, the
microprocessor saves the status of the Standby/On key.
Front module controller
The front module controller accommodates all the components that are required on one board - for
example, the processor, memory chips (SIMMs), I/O chips, the lithium battery, IEC/IEEE bus controller,
ethernet interface, HD controller, USB controller, LCD graphics controller, external monitor graphics
interface (Monitor).
Only up to FMR7: Two serial interfaces (COM1/2), a parallel interface (LPT), floppy controller and a
connector for an external keyboard (keyboard PS/2).
Hard disk
The hard disk is screwed to the rear of the tray for the front module controller with a holder and
connected to the board with a flat cable.
Power supply
The power supply produces all the voltages required to power the ZVA. It can be turned off with a
switch on the instrument’s rear panel.
The power supply is a primary-switched power supply with power factor correction (PFC) and standby
circuit (+12 V standby).
On the secondary side, it outputs DC voltages (+3.4 V, +5.2 V, +6.5 V, +8.25 V, +12.25 V, +12 V
standby, -12.25 V).
The control signal RS_PS_ON which is controlled by the front module controller (via the
STANDBY/ON
key at the front of the instrument frame), activates the power supply. In the standby mode, the power
supply generates only the 12-V standby voltage to supply a crystal oven and the STANDBY status
display on the front panel.
The secondary voltages are open-proof and short-proof to ground and mutually open-proof and short-
proof.
A circuit that prevents overheating is also provided. Overheating is indicated to the front module
controller via a status signal (
OT ).