Adjustments
Model
8642AjB
5-1. ADJUSTMENTS
If
a
repair
is
done
by
the"
Module
Exchange" method,
no
adjustment
of
the
HP
8642
or
the
exchange
module
is
necessary.
If
a
component
level repair
is
performed
on
a module, it will be necessary
to
do
its
Manual
Adjustments
and/or
Auto-Adjust
Procedures
to
ensure
its
I/O
spec's.
Due
to
the
modular
nature
of
the
HP
8642, the
adjustment
of
a
module
will
not
effect
other
modules
in
the
instrument.
After the repair
of
a module,
it
is
only
necessary
to
adjust
that
module.
Therefore,
the
adjustments
have been integrated
into
the
Troubleshooting
r
nformation
in
Section
8.
For
example: After
two
years
of
operation
you find that
AM
distortion
performance
is
at
the
extreme
limits given in
Table
I-I.
After using
Module
Substitution (see On-Site Service
Manual)
to
isolate
the
problem
to
A13,
you
turn
to
the
A13 tab
in
Section
8.
You
perform
the
AM
Distortion
Adjustment
followed by
the
A
13
Auto-Adjust Routine.
The
AM distortion
performance
is
now
returned
to
nominal.
5-2. AUTO-ADJUST ROUTINES
5-2
Description:
In
the
service
documentation
for the
HP
8642
there
will be
references
to
Self-Cal, Self-Calibration,
and
Auto-Adjust.
These
three
terms
refer
to
the
same
firmware routines built
into
the
HP
8642
that
are used
to
regenerate
module
correction
data
(sometimes
refered
to
as Cal Data).
The
Cal
Data
is
stored
in
EEPROM
on
the A3 board
and
is
used
to
control
the
modules
during
instrument
operation.
A back-up
copy
of
the Cal Data
is
stored in
EEPROM
on
the
AlO
board,
which
is
located
under
MP
65
on
the
rear
panel.
The
Auto-Adjust
routines
control
external
measurement
equipment
via HP-IB for
the
purpose
of
regenerating
Al,
A6,
All,
A12,
AD,
and
AI4
module
correction
data, after a
component
level
repair
of
the
module. External
measurement
equipment
required
includes; a
voltmeter,
printer,
and
HP
8902A. In
some
cases an
HP
8901
B may be substituted for
the
HP
8902A.
The
printer
must
have
HP-IB capability (such
as
an
HP
2225A).
The
voltmeter
must
also have
HP-IB
capability;
an
HP
3478,
HP
3455
or
HP
3456 are
some
voltmeters
that
can
be used. A list
of
equipment
needed
for
each
Auto-Adjust
Routine
is
given
in
Table 5-1. At
HP
8642
power
up,
denwlt
HP-IB
addresses
are
assumed (see
Table
5-2.)
If
the
HP-lB
nddresses
of
the external
equipment
nrc
different
from
the
default values, usc
the
service special fUllctions given in
Table
5-2
to
re-define
the
addresses
the
H P 8642 will use.
Tah/e
5-1.
Rcquired
EqlliplIlell(
/iJI'
A
lI(o-A(~jIlS(.
-_
..
_.
Module
HP-IB
Printer HP-IB
DVM
HP 8902A
A2 Yes Yes
No
A6 Yes Yes Yes
or
HP 8901A/B
A11
Yes
Yes Yes
A12 Yes
Yes
Yes
or
HP 8901A/B
A13 Yes
Yes
Yes
A14 Yes No Yes
Table 5-2.
Challgillg
(he
Ddalll( HP-1B A
ddre~\e\.
(".Y
.
.\""
= New
(WD
diglf
HP-1I3
add,.e~~.)
Instrument
Default
Service Special Function
HP-IB
Address
Key Sequence
Printer
01
81
XX
Hz
HP
8901
A/B, HP 8902A 14
82
XX
Hz
DVM
23
83
XX
Hz
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