E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Overall Description
1-84
front panel may have modulation input/output BNC connectors installed but not operational if the option associated
with that connector is not also installed.
When line voltage is present and the signal generator is in standby mode, the amber LED above the power switch
lights. When the signal generator is in power–on mode, the green LED (also above the power switch) lights.
Hardkeys/Softkeys
The front panel has two types of keys:
Hardkeys are dedicated to specific functions, entering values for the most commonly used features, and controlling the
display’s contrast and intensity.
The front panel keypad uses a row and column configuration. Pressing a key makes a connection between a row and
column. The row and column information is routed to the A18 CPU where it is interpreted, and the corresponding
function executed.
Softkeys, located along the display, are used to select the function displayed to the left of the key (on the display).
When a softkey is pressed, the displayed function changes.
A2 Display
A liquid crystal display (LCD) provides information about the instrument's settings and condition. The LCD requires a
power supply, lighting, and data:
• The A4 inverter converts dc voltage to the ac voltage required by the display.
• A backlight (a bulb powered by the A4 Inverter) lights the display so that information is visible.
• The A18 CPU generates data, which is routed to the LCD through the A3 Power Switch assembly.
• To extend the life of the LCD, an available sleep mode turns the LCD off after a defined inactive period (no key
presses or program commands) and turns it back on with any key press.
RF Output Connector
On 20 GHz instruments, the RF output connector is an APC 3.5 male or Type–N (Option 1ED). On models with output
frequencies above 20 GHz and <
50 GHz, the RF output connector is a 2.4 mm male. On models with output
frequencies above 50 GHz, the RF output connector is a 1.85 mm male connector. Option 1EM moves all front panel
connectors to the rear panel.
Rear Panel
The rear panel contains the power line module, LAN, GPIB, RS–232, and A20 Source Module Interface (SMI), scalar
interface, and BNC connectors used for sweep interface. BNC and SMB connectors may be present on the rear panel
but not operational if the option associated with that connector is not installed.
Frequency Generation
The YIG oscillator generates frequencies from 3.2 to 10 GHz.
Output
Frequency
Oscillator
Frequency
Path Notes
< 250 MHz 3.2 to 10 GHz
Lowband path,
and part of
highband path
A6 Frac–N signal is mixed with a 1 GHz signal on the A8 output
assembly;
the difference is used to generate the lower frequencies.
250 MHz
to
3.2 GHz
4 to 8 GHz Oscillator output is divided by 2/4/8/16 on the A6 Frac–N assembly.
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