HP 8647A - Page 112

Col 1 col2 -13 cOl4 col5
Col6
A3J3-1 A3J3-2 A3J3-3 A3J3-4 A3J3-5
A3J3-6
Row 1
e FREQUENCY INCR 7 8 9
A3J3-9 (fres) SET
Row 2
=+
AMPLITUDE
TI 4 5 6
Row 3
REF
FM
U 1 2 3
A3J3-10 (fred
A3J3-11
SET
(fred
Row
4 REF AM 4M 0 f
A3J3-12 ON/OFF
(fred
Row
5 ADRS SAV REG fr MOD INT
A3J3-13 (memory) ONlOFF 400 Hz
Row 6 LOCAL DEL SEQ U 1 kHz + INT
A3J3-14 (memory) EXT DC 1 kHz
Row 7 e 3 REF REF RF ATTN
A3J3-15 (ampl) (rnP1) SET ON/OFF ON/OFF HOLD
(amp11 (amp11
Row
8
c mV PV
dBpV
A3J3-16 (back space) emf emf emf
A2 Power Supply
The power supply is a switching power supply producing 4 voltages;
+ 5 V, + 15 V, - 15 V, and + 38 V. The switching supply will only
regulate when connected to a load. The power supply receives mains
(line) voltage through the power switch on the front panel and the
line module on the rear panel. Post regulation on the
A3 assembly
produces k12
V, filtered + 5 V, and + 5 V.
Col 7
A3J3-7
MHz
dB(m)
kHz
mV
%
PV
rad
dBpV
EXT
AC
EXT
DC
A3 Motherboard
The motherboard contains four functional blocks: modulation
distribution, controller, post regulation, and diagnostic latching.
The modulation distribution block produces two level-calibrated
modulation frequencies,
1 kHz and 400 Hz. The frequencies are
derived by dividing a
200 kHz signal from the A4 reference module
by
200 and 250. The internal signals are leveled by an amplifier and a
12-bit
DAC. The signals are then routed to the A5 sig gen synth when
FM is enabled, or to the A6 output for
AM.
When internal modulation is turned on, the signal is also routed to the
front panel
MOD INPUT/OUTPUT connector. External modulation
signals are also routed through the modulation distribution block.
External signals can be either ac- or dc-coupled. The modulation
signals can
be checked at A3TPl for the FM signal and at A3TP2 for
the
AM signal.
The controller contains
the microprocessor, memory, serial I/O for the
other assemblies, HP-IB, front-panel control, and serial interface for
the external control options. Memory is broken into four sections;
EEPROMs,
ROM, volatile SRAM and non-volatile battery-backed
SRAM. The
ROMs are contained on a separate memory board, A3A1.
Theory of Operation 5a-3