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3.
Allow input capacitors two minutes to discharge
before making resistance checks or removing com¬
ponents in primary circuit.
4.
Unless otherwise noted, all voltages on the power
mesh and control board assemblies are measured
with respect to bias common, available at A2U1
heatsink. Voltages on the HP-IB/microcomputer
assembly are measured with respect to either
or
\2? , which should be shorted together for
troubleshooting.Vl7is available at TP1 and wire loop
Wr/!\2/is available at TP2, TP3, and wire loop W18.
Voltages on the front-_£>anel assembly are measured
with respect to either\2,^r\^ available at wire loops
on the front-panel printed circuit board.
5.
Numbers in brackets refer to waveforms shown in
Figure 5 21.
6.
Unless
arrows
point,
otherwise,
flow
of
troubleshooting trees is down and to the right.
7.
The troubleshooting trees provide general guidelines
to help isolate trouble. They will not isolate all possi¬
ble troubles. The user should use signal tracing and
other standard troubleshooting techniques to iden¬
tify faulty components. The user is responsible for
connecting and adjusting meters, oscilloscopes, etc.
properly. Before replacing a component, check con¬
nections to the component and ensure that bias
voltages to the component are correct .
8.
Test programs are given for two HP controllers; HP
9825 or 9826 programs are on the left, HP 85 programs
are on the right.
9.
Table 5-4 provides descriptions of the control board
test points. Table 5-5 proves descriptions of the HP-
IB /microcomputer test points.
10.
After isolating and correcting a problem, go back to
the beginning of main troubleshooting tree. Figure
5-16, unless otherwise directed.
5-81
Troubleshooting Test Setup. Unless otherwise
noted, troubleshooting procedures should start with the
following test setup,
1.
Turn off 6034A and disconnect all loads.
2.
Strap rear panel terminal block for local sensing, and
no connections to A1 and A2, as shown in
Figure 3 3,
3.
For procedures that call for a load resistor, connect a
200-ohm
10 watt
load
resistor
across
output
terminals,
4.
Turn OVP ADJUST control to maximum (fully
clockwise.)
5.
Remove top cover,
6.
Short together test points TP1 and TP2 or TP1 and
TP3 on HP-IB/microcomputer assembly.
5-83
The
easiest
and
most
efficient
method
of
troubleshooting
microprocessor-based
instruments
is
signature analysis. Signature analysis is similar to signal trac¬
ing with an oscilloscope in linear circuits. Part of the
microcomputer memory is dedicated to signature analysis,
and a known bit stream is generated to stimulate as many
nodes as possible within the circuit. However, because it is vir¬
tually impossible to analyze a bit stream with an oscilloscope,
a signature analyzer is used to compress the bit stream into a
four-character signature that is unique for each node. By com¬
paring signatures of the unit under test to the correct
signatures for each node, faults can usually be isolated to one
or two components.
Note that signature analysis provides
only go/no go information; the signature provides ab¬
solutely no diagnostic information,,
5-84
Start, stop, and clock signals for the signature
analyzer are provided by the unit under test.
Table 5 4. Control Board Test Point Descriptions
Test Point
Connector
P2
Description
1
CV Programming Voltage
2
•••" Sense
3
1 Monitor Buffer Amplifier Output
4
Overvoltage Status (low = overvoltage)
5
+ Sense
6
Outboard Sense (outboard side of
current-monitor resistor)
7
CC Programming Voltage
8
-12 V Unregulated { * -25 V)
9
Constant Voltage Mode (low- CV)
10
Overvoltage Remote Reset Input
11
f 15 V Unregulated (=* +25 V)
12
Bias Power Supplies Common
13
Low Bias Voltage or AC dropout
(low = low bias or ac dropout)
14
Over Temperature Status
(low - over temperature)
15
Constant Current Mode (low=CC)
16
+ 5 V Unregulated (•» + 16 V)
17
Signal to "On" Driver
18
Signal to "Off" Driver
19
(Not used)
20
+ 15 V Regulated
21
+ 5 V Regulated
22
Inboard Sense (inboard side of
current-monitor resistor)
23
20 kHz Clock Signal
24
12 V Regulated
25
(Not used)
26
Ip (Primary Current) Ramp Voltage
5-16
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