HP 3438A Operating And Service Manual page 65

Model 343814
Section V l l l
8-58. Test Pads. Logic control states for the A I P C
significantly from zero. troubleshoot the lnput Amplifier
assembly ( H i =
+
7 V, Low = 0 V) can be evaluated using first.
the test pads. r a b l e 8 - 7 lists t h e test pad by number and its
associated function. 8-64. T h e gains for the lnput a n d Post Amplifiers can be
Table 8-7. Test Pads.
8-59. Power Supply. If the
+
7 V a n d / o r the -7 V
supply reads low at the test pads, turn S I O F F a n d re-
check for + 7 V and -7 V a t a point prior t o t h e S l . Refer
t o schematic no. 4. This will verify if the problem is in the
power supply rather than in the Multimeter circuitry.
Figure 8-10 shows the jumper configuration for the
+
7 V
and -7 V power supplies.
No.
1
2
3
4
5
8-60. V ~ I I H is t h e substrate voltage for U l I , U 12. and
U 13. If this voltage is incorrect. individually opening J M
403, J M 404. a n d J M 402 while monitoring the VSIIH
voltage will isolate the faulty integrated circuit.
8-61. A1 and A2 Troubleshooting.
Usage
Run U p Enable
: : ; I
pc:pn
FNC Code
MRF Manual Range
Switch Code
8-62. Analog Troubleshooting. Failures in the
analog circuitry can best be analyzed by studying the
Simplified Analog Schematic, Figure 8- 12.
NOTE
No.
6
7
8
9
10
verified by-stopping the measurement cycie during run-
up. This is accomplished by shorting U 13(35) t o ground
during run-up. This stops the controller clock and leaves
the gain selector switches set for run-up. A dcvoltage can
Usage
MRE Manual Range
Switch Code
MRD Manual Range
Switch Code
Digital Ground
Run Down
Compensation (+)
No Connection
be used in each range t o signal trace the stage gain of the
lnput a n d Post Amplifiers.
8-65. Logic Troubleshooting. T h e Multirneter Logic
can best be tested by the following procedure:
a. With 5403 still disconnected-open JM202.
b. Connect the controller (U13) side of J M 2 0 2 t o
. I M203.
c. T h e display t o indicate all zeros except when a
"Improper" switch combination is selected (Refer t o
Section Ill).
8-66. If this test fails, there is a problem in the Logic
portion of the Multimeter. If it passes. the problem is
most likely t o be in the Analog portion.
NOTE
The Adjusrtnenr Proc,rclurr tn~i.s/ he
prrf'ortnrcl and rhr Ahhrc~viarrd Per/brtnutlc,r
Tes/ c,otnplr~erl h e f i r r ussutning rhr
M~ilritnerer has f'ailrd. .Munj* hours
r?/'
rrouhle.shooring (,an ht, \c~aisrc~J her.au.se o / a n
ovrrlooked ad;usrtnrrzr.
8-67. HP-IB (A3) Troubleshooting.
8-68. T h e A3 PC assembly can best be troubleshot using
the -hp- 5004A Signature Analyzer ( S A ) and the
Troubleshooting Flow Charts given in Figure 8-1 1.
8-63. T h e Input and Post Amplifiers c a n be isolated by 8-69. Signature Analyzer (SA). Throughout the
placing a short between the COM and A m p s input following Flow Chart, the S A switch settings and
terminals. This forces the Multimeter into Auto Zero. connectors will be given except the ground lead
Therefore, the outputs of either Amplifier should be connection. I'he ground lead is connected to the GNL)
approximately zero volts. If both amplifiers a r e offset jumper on the A3 P C assembly for the entire test.
POWER SUPPLY JUMPERS
J M 4 0 5 J M 4 0 6
- 7 v
V
J M 4 0 7
dM408
I
N O T E
i h l
405THROIIC,H
JM
408
A H 6 NOT
6HUPLN OW T H E
S C t l t M A T I C D l A G H A M S
I
Figure 8-10. Power Supply Jumpers.
8-9