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Col 1
c o l 2
-13
cOl4
c o l 5
C o l 6
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
T I
4
5
6
Row 3
REF
F M
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
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