HP 8560A, Service Manual

Page: 248 / 450

EEROM
The EEROM stores important amplitude-related correction data. This includes data for
mixer-bias
and RF Gain (flatness correction). The analyzer serial number,
model number, and installed options are also stored in EEROM.
Firmware
The analyzer firmware reads the model number and installed options from the EEROM to
determine how to respond to certain keystrokes.
Display ASM
Much of the miscellaneous digital control is performed by functions as the
display ASM (Algorithmic State Machine) and character ROM. It also converts the
CPU data bus to an 8-bit data bus for the rest of the analyzer.
Display/Power Supply Section
A6 Power Supply
The A6 Power Supply is a switching supply operating at 40 for the low voltages and
30 for the CRT supplies (cathode, filament, Vdc, and post accelerator). High
Voltage Module contains the high-voltage transformer and post-accelerator multiplier. Power
is distributed through W8 to Al7 and through
to the rest of the assemblies.
supplies CRT cathode and filament voltages to the Al7 assembly.
The speed of the analyzer’s fan is variable. A thermistor on A6 senses the temperature
and adjusts the fan speed accordingly. This allows the analyzer to run quietly in most
room-temperature environments and faster (louder) only when necessary.
Al7 CRT Display Driver
The Line Generators on the A2 assembly drive the Al7 CRT Driver. The Al7 assembly
contains X and Y Deflection Amplifiers, focus and intensity grid amplifiers, and miscellaneous
CRT bias circuitry. The high voltage is supplied by
High Voltage Module.
In fast-analog zero-span mode (sweep times ms), the O-SPAN VIDEO signal from A3 and
the sweep ramp from Al4 goes to the Al7 CRT Driver. The graticule and annotation is still
digitally drawn.
General Troubleshooting 6-43