HP 54501A - Block Level Theory; Power Supply Assembly; Display Monitor Assembly

6-4 . BLOCK LEVEL
THEORY OF
OPERATION
TheHP Model 54501A is a four-channel 100
MHz digitizing oscilloscope .
The human inter-
face is a front-panel knob
and keypad for in-
strument control
and
9"
(diagonal) green
phosphor CRT
for information display .
Available on
the rear panel is an
HP-IB
con-
nector for communication to a
printer or from
a controller . Two
oscilloscope outputs are
also available on
the rear panel through
BNC
connectors :

one for do calibration
andone
for
ac
calibration and probe
compensation .
The hardware of the HP 54501
A consists of
four main modules .
Figure 6-1 is a simplified
block diagram of
the four main assemblies .
Also,
in
the
diagram are rear panel connectors
and the
Intensity adjustment .
This manual supports
troubleshooting to main
assembly level .
Theory of operation for the
System Board
Assembly is included for infor-
mation
only and is not intended
for
troubleshooting purposes
.
6-5 . Power Supply
Assembly
The Power Supply
Assembly of the HP 54501A
is a 120 W switching
power supply . It has a
do output
power connector and cable that
connects
to the System Board
Assembly . The
ac
input range to the power
supply is 115V or
230 V and has
maximum power of 200 W
when operating at
48 - 66 Hz .
The Power Supply
Assembly provides
all
vol-
tages necessary
to operate
the HP
54501A to
the System
Board Assembly .
Unfiltered vol-
tages
of + 15V, -15V,
+12V, -12V, +5 .15V, and
-5 .2V are supplied to the
board where they are
then filtered and distributed
throughout the
board
and to the Display
Monitor Assembly .
Filtered voltages of
approximately +5 V and
+12 V are routed through the
System Board
Assembly
to the Display Monitor
Assembly .
The +5 .15
V supply is adjustable .
The adjust-
ment procedure
is in section 4 of this
manual .
6-6 . Display Monitor Assembly
6-7 . System Board Assembly
HP 54501A SERVICE
The Display Monitor Assembly consists of the
sweep board circuitry, a 9-inch green phos-
phor display
CRT,
and
the CRT yoke . The as-
sembly requires
+
5
V and +12 V from the
power supply
via the System Board Assembly .
The CRT is a non-interlacing raster display
controlled by
the
CPU
portion of the
System
Board
Assembly . System control provides
synchronization and pixel information .
The System Board Assembly contains
the
ac-
quisition system
and system control circuitry .
It
also
provides interfaces for the Power
Supply Assembly, Display Monitor Assembly,
keypad, RPG, and HP-IB . The input to the
System Board Assembly
from the target
sys-
tem is from
any
or
all four channels located at
the
front panel BNCs . The user interface is
from the front-panel keyboard or with a con-
troller via the HP-IB
connector located on the
rear panel
. A more detailed theory of the
System
Board Assembly follows this block
level theory .
6-8 . Keypad
and Knob Assembly
The front-panel keypad of the HP 54501A is
elastomeric and has
44
keys . Twenty
of the
keys are
single-function, 17 are dual-function,
and the
remaining 7 are display softkeys with
variable
functions depending on the displayed
menu .
The keyboard rows are continually
scanned
at a frequency of 60 Hz and when a
key
is
pressed, the signal is sent as data to
the
68000 which determines
the
key
pressed and
its function .
The RPG (Rotary Pulse
Generator) is control-
led by the
front-panel knob and supplies pul-
ses to the 68000
microprocessor when the
knob is turned .
The RPG
is
used to dial in
values for various
settings
of
the displayed
menu . The RPG will
normally
be
set in coarse
mode but may be used in
fine mode
by
press-
ing the front-panel toggle key above
the RPG
labeled FINE .