HP 3400A Service Manual

c.
Connect
the
multimeter
between
pins
10
and
14
on
the
A6
socket.
This
checks
the
heater
of
TC402.
Make
sure
the
reading
is
between
76.5
ohms
and
103.5
ohms.
Replace
the
ther-
mocouples
if
out
of
limits.
d.
Connect
the
1
Kohm
resistor
to
the
power
supply
as
shown
in
Figure
5-5.
Make sure the power supply is adjusted to O V before turning it
on. Also, do not apply more than 7 V to the thermocouples, or
they may be damaged.
e.
Connect
the
power
supply
and
1
Kohm
resistor
between
the
junction
of
C413
and
C415,
and
ground.
This
checks
the
TC401
output
voltage.
Refer
to
Figure
5-5
and
connect
the
HI
lead
of
the
multimeter
to
point
A
and
the
low
lead
to
point
B
(i.e.,
across
the
resistor).
Turn
the
power
supply
on
and
adjust
it
for
a
5
V
reading
on
the
multimeter.
f.
Remove
the
multimeter
and
then
connect
it
as
follows:
LO Input: to pin 11 on the A6 socket
HI input: to pin 13 on the A6 socket
g.
Note
the
reading
on
the
multimeter.
It
should
display
between
+6.5
mV
and
+9
mV.
If
the
reading
is
out
of
the
specified
limits,
replace
the
thermocouples.
h.
Set
the
power
supply
output
to
0
V
and
disconnect
it
from
the
thermocouples.
NOTE
The
following
check
applies
to
-hp-
3400A’s
with
serial
number
prefix
2225
and
above.
For
instruments
that
have
a
lower
prefix,
change
step
i
to
the
following:
POWER
SUPPLY
PoAL
AE
Ge
eS
A
ee
~hp-
62145
:
TO C413
& C415
THERMOCOUPLE | POWER. SUPELY
CONNECTION
ae + to C443/C475
[
TC4O4
|
-
to
GROUND
|
Lo 0-0 + -
i Tea + to U5 (10)
oie | = to JS (14)
3400 5-5
Figure 5-5. Testing the Thermocouples

HP 3400A Specifications

General

Brand	HP
Model	3400A
Category	Measuring Instruments
Language	English