HP 3457A - Page 162

de
Ab
ta
3457A Replaceable Parts
Table 6-5. List of Part Changes
Operational Amplifier A2U516, part no. 1826-0635 (OP-07CP), has been replaced with part
no. 1826-1382 to achieve better initial time drift of VOS to guarantee 90 day/l year
specifications, Ferrite Slab A2US02A (part no. 1200-1207) has been added to eliminate RFI
generated by A2U502. Inductor A2L501, part no. 9100-1788, has been replaced by a jumper
wire
(A2JM503)
to
reduce
power
supply
noise
generated
by
Processor
A2ZUSOl.
These
im-
provements
have
been
implemented
on
A2
Assemblies
which
have
an
ERC
(Engineering
Revision Code) of 2521 or greater.
Operational Amplifiers A2U211 and A2U212, part no. 1826-1133 (LMIICH) have been
replaced, in all applications, with part no. 1826-1381 to reduce noise and improve offset
drift.
The
new
part
will
be
found
on
A2
Assemblies
which
have
an
ERC
of
2524
or
greater.
Resistor A2R122, part no. 0757-0410 (3019) has been replaced, in all applications, with part
.no 0757-0284 (1500) to eliminate a parasitic oscillation which causes an excessive input cur-
rent in A2U101. The new part will be found on A2 Assemblies which have an ERC of 2529
or greater.
Resistor A2R219, part no. 0757-0442 (10KQ) has been added to provide extra operating mar-
gin for A2U214, This part will be found on A2 Assemblies which have an ERC of 2551 or
greater. Printed circuit board becomes Revision B.
EPROM
A1U502,
part
no.
03457-88803,
has
been
replaced
by
part
no.
03457-88804
to
correct
a
"trigger
too
fast"
error
when
external
trigger
was
executed
from
program
memory,
This
part
will
be
found
on
Al
Assemblies
which
have an
ERC
of
2609
or
greater.
Relay A2K106, part no. 5180-8233 has been replaced, in all applications, with part no.
0490-1556.
This
change
was
made
to
standardize
part
useage
with
a
higher
quality
part.
Relays
A2K107,
A2K201,
A2K301
and
A2K302,
part
no.
5180-8234
has
been
replaced,
in
all
applications,
with
part no,
0490-1555.
This
change
was
made
to
provide
a
higher
quality
part
and
standardize
part
useage.
Relays AIK851 through AIK860, part no. 0490-1461, have been replaced, in all applications,
with part no, 0490-1576 to standardize relay usage and reduce cost. These parts will be found
on HP 44492 PC Assemblies which have an ERC of 2644 or greater.
Capacitors A2C532 and A2C533, part no. 0160-2343 (100pf) have been added to A2
Assemblies to reduce the common mode signal present at A2J501. These parts will be found
on A2 Assemblies which have an ERC of 2703 or greater. Printed circuit board becomes
Revision C.
The Al Main Controller Assembly (part no. 03457-66501) has been replaced with the All
Main Controller Assembly (part no. 03457-66511). This change was made to add Option 700
(CHIL language). The All assembly is a direct replacement for the Al assembly.
Resistor A2R505, part no. 0757-0465 (100Kq) has been replaced. in all applications, with part
no. 0757-0472 (200Kq) to insure that the microprocessor (A2US01) always starts with a reset
signal at turn-on, The new part will be found on A2 Assemblies with an ERC of 2708 and
greater.
EPROM A1U502 (part no. 03457-88804) has been replaced, in all applications, by part no.
03457-88805
to
correct
a
timing
error
of
the
"voltmeter
complete"
signal
when
using
the
4-Wire Ohms function and to eliminate the possibilty of shorting two input channels when a
"device clear" signal is received while the instrument is executing a scan list.
6-25