Tektronix P6042 PROBE User manual

INSTRUCTION
MANUAL
Serial Number
P6042
PROBE
Tektronix, Inc.
S.W. Millikan Way • P. O. Box 500 • Beaverton, Oregon 97005 • Phone 44-01 1 • Cables: Tektronix
070-0629-00
967

All Tektronix instruments are warrante
against efective materials an workman 
ship for one year. Tektronix transformers,
manufacture in our own plant, are war 
rante for the life of the instrument.
Any questions with respect to the war 
ranty mentione above shoul be taken
up with your Tektronix Fiel Engineer.
Tektronix repair an replacement-part
service is geare irectly to the fiel ,
therefore all requests for repairs an re 
placement parts shoul be irecte to
the Tektronix Fiel Office or representative
in your area. This proce ure will assure
you the fastest possible service. Please
inclu e the instrument Type an Serial or
Mo el Number with all requests for parts
or service.
Specifications an price change privi 
leges reserve .
Copyright ® 1967 by Tektronix, Inc.,
Beaverton, Oregon. Printe in the Unite
States of America. All rights reserve .
Contents of this publication may not be
repro uce in any form without permission
of the copyright owner-
WARRANTY

Characteristics — Type P6042
Fig. 1-1. P6042 Current Probe an accessories.

Type P6042
SECTION 1
CHARACTERISTICS
Change information, if any, affecting this section is found at the rear of the manual.
Intro uction
The Tektronix P 042 Current Probe is designed for use with
oscilloscope systems having either 50-ohm or high-impedance
inputs. DC and low-frequency current waveforms, as well
as measurements to 50 MHz, can be made accurately and
quickly with the probe. To achieve tilt-free display of the cur 
rent waveform, a Hall Voltage device is used in the probe to
supply the DC and low-frequency information to the P 042
amplifier. In the amplifier, low-frequency information is
combined with the high-frequency component of the signal
and the resultant is developed at the output.
The P 042 is powered by a regulated power supply con 
tained within the instrument, independent of associated test
equipment.
Electrical Characteristics
The electrical characteristics given in Table 1-1 apply over
an ambient temperature range from 0° to + 50°C, after the
probe has been calibrated at + 25°C ±5%. Warmup time
is 5 minutes. Under these conditions, the P 042 Current Probe
will meet or exceed the requirements given in the Performance
Requirement column of the table when the instrument is used
with a 100 MHz oscilloscope (such as the Type 47A with
10A2A and 11B2A plug-in units). The specifications listed in
the table include only the performance of the P 042 Current
Probe. Any error introduced by the test equipment must be
added to the applicable performance requirements. Per 
formance of the probe is checked to these requirments in the
Performance Check section of this manual. If the need for
calibration is indicated, a step-by-step procedure is provided
in the Calibration section.
The Supplemental Information column of Table 1-1 provides
additional information about the probe and describes cer 
tain conditions that pertain to the performance requirements.
Any characteristics given in the Supplemental Information
column are not requirements in themselves, and are not
necessarily checked in the manual procedures.
Environmental Characteristics
The environmental performance of the P 042 Current Probe,
a laboratory instrument, is checked at the factory and found
to meet the requirements described in Table 1-2.
TABLE 1-1
ELECTRICAL CHARACTERISTICS
Characteristic
Bandwidth
Performance Requirement
DC to 50 MHz.
Supplemental Information
3 dB down.
Transient Response
Risetime
<7 ns. Calculated from bandwidth.
Aberrations
≤ 3% from 1 mA/DIV to 50 mA/DIV.
±5% from .1 A/DIV to 1 A/DIV before
first 100 ns.
Noise
Periodic and Random Deviations ≤ 0.5 mA + 0.2 div, tangentially measured.
Random Trace Shift
≤ 1.5 mA. 0.1 Hz to 100 Hz (on selectable bandwidth
system).
Dynamic Range
+500 mV to — 500 mV at probe amplifier
output.
+ond — 10 div with oscilloscope set to
50 mV/div.
Compression at limits of
5% or less.
dynamic range.
Positioning Range
+300 mV to — 300 mV at probe amplifier
+ and - — div with oscilloscope set to 50
output.
mV/div.
Attenuator Accuracy
Within ±3%.
Insertion Impedance
Typically 0.1  at 5 MHz. See Fig, V2 for impedance vs. frequency
curve.
Maximum Input Current
1 A to 5 mA: 10 A (DC + peak AC). See
Fig. 1-3 for derating curve. 2 mA and 1
mA: 0.5 A (DC + peak AC).
Thermal Drift (Probe only)
≤ 2mA/°C from 15°C to +35°C with
amplifier temperature constant.
Thermal Drift (Amplifier only)
≤ 0.2 div/ °C with probe temperature con 
stant.
1-1

Characteristics — Type P6042
TABLE 1-1 (cont)
ELECTRICAL CHARACTERISTICS
Characteristic
Performance Requirement Supplemental Information
Voltage-Feedthrough
Susceptibility
≤ 250 µ A/V at 50 MHz.
External Magnetic Field
Susceptibility
≤ 250 µA/Gauss, at 0 Hz.
Required Output Load Impedance
50 .
Line Voltage Regulation
90 to 13 V RMS or 180 to 272 V RMS.
1.3 crest factor; 3 taps available in each
range.
Power Supply Ripple
≤ 2 mV peak to peak.
Input Power
≤ 20 W.
Input Frequency
50 to 400 Hz.
TABLE 1-2
ENVIRNOMENTÂL CHARACTERISTICS
Characteristic Performance Requirement
Supplemental Information
Temperature
Non-operating – 40° C to + 5° C.
Operating 0°C to +50°C Ambient.
Altitude
Non-operating
To 50,000 feet.
Operating
To 15,000 feet.
Humidity (Non-operating) 5 cycles MIL-STD 202C, Method 10 B, omit 
ting freezing and vibration cycles.
Vibration (operating) 15 minutes along each axis at .015 inch
Tested with instrument secured to vibrati
total displacement with frequency varied
from 10-50-10 cycles per second in 1 -minute
cycles. Three minutes at any resonant
point or at 50 cycles per second.
platform.
Shock (Non-operating)
30 g's, ½ sine, 11 ms duration, 2 shocks
Guillotine-type shocks.
per axis.
Transportation
Package Vibration
1 hour at 1 g.
Package just leaves vibration surface.
Package Drop
30 inches on 1 corner, all edges radiating
from that corner, and all flat edges.
1-2

Characteristics — Type P6042
®ï
1-3

Characteristics — Type P6042
1-4

Type P6042
SECTION 2
OPERATING INSTRUCTIONS
Change information, if any, affecting this section is found at the rear of the manual.
General
The P 042 Current Probe is designed to work into either a
50-ohm system or a high impedance oscilloscope using a
50-ohm termination. This section of the manual describes the
use of the P 042 Current Probe. Information in this section
is given to aid in making accurate measurements with the
probe.
Han ling
The P 042 is designed to be as rugged as possible,
consistent with good high-frequency response and size. How 
ever, as with all precision devices, the probe and cable
should be handled with care to avoid damage. Special care
should be taken that the cable not be crushed, kinked, or
pulled. Avoid dropping the probe, as some of the most sen 
sitive circuitry is located within the probe assembly.
Operating Voltage
The P 042 can be powered from either a 115-volt or a 230-
volt nominal line voltage source. The line voltage selector
assembly on the rear panel converts the instrument from
one operating range to the other. In addition, this switch
assembly changes the primary connections of the power
transformer to allow selection of one of three regulating
ranges. The assembly also includes the two line fuses. When
the instrument is converted from 115-volt to 230-volt nominal
operation, or vice versa, the switch assembly connects or
disconnects one of the fuses to provide the correct protec 
tion for the instrument. Use the following procedure to con 
vert this instrument between nominal line voltages or reg 
ulating ranges.
1. Disconnect the instrument from the power source.
2. Loosen the two captive screws which hold the cover
onto the switch assembly; then pull to remove the cover.
3. To convert from 115-volt to 230-volt operation, pull out
the Voltage Selector switch bar (see Fig. 2-1); turn it around
and plug into the remaining holes. Change the power cord
to match the powersource receptacle or use a 11 5-volt to
230-volt plug adapter.
4. To change regulating ranges, pull out the Range Selec 
tor switch bar (see Fig. 2-1); slide it to the desired position
and plug it back in. Select a range which is centered about
the average line voltage to which the instrument will be con 
nected (see Table 2-1).
5. Re-install the cover and tighten the two captive screws.
. Before applying power to the instrument, check that the
indicating tabs on the switch bars are protruding through the
correct holes for the desired nominal line voltage and regulat 
ing range.
Fig. 2-1. Line Voltage Selector assembly on the rear panel (shown
with cover remove ).
CAUTION
The P 042 should not be operated with the Volt 
age Selector and Range Selector switches in the
wrong position for the line voltage applied. Opera 
tion of the instrument with the switches in the
wrong positions will either provide incorrect opera 
tion or damage the instrument.
TABLE 2-1
Regulating Ranges
Range Selector
Switch Position
Regulating Range
115-Volts
Nominal
230-Volts
Nominal
LO (switch bar in left
holes)
90 to 110 volts
180 to 220 volts
M (switch bar in mid 
dle holes)
104 to 12 volts 208 to 252 volts
HI (switch bar in right
holes)
112 to 13 volts
224 to 272 volts
Operating Temperature
The P 042 depends upon convection cooling to maintain
a safe operating temperature. Adequate clearance on all
sides must be provided to allow heat to be dissipated away
from the instrument. Do not block or restrict the air flow
2-1

Operating Instructions — Type P6042
Fig. 2-2. Function of front panel controls an connectors.
2-2

Operating Instructions — Type P6042
through the holes in the cabinet. The clearance provided by
the feet on the bottom of the instrument should be main 
tained. Provide at least three inches of clearance at the sides
and top (more if possible). The instrument can be operated
where the ambient air temperature is between 0°C and
+50°C.
Controls an Connectors
Fig. 2-2 shows the front-panel controls and connectors on
the P 042 and describes the function of each.
Installation
When shipped from the factory, the P 042 is ready to be
used with either a 50-ohm system or a high-impedance
oscilloscope and has been factory calibrated to meet the
specifications listed in Section 1. Due to normal differences
in oscilloscope input characteristics, however, the high-fre 
quency response of the probe should be checked on the
system with which it is to be used before making critical
high-frequency current measurements.
If the instrument is to be operated with a high-impedance
oscilloscope connect the 50-ohm termination (011-0049-00),
supplied in the accessory kit, to the input connector of the
oscilloscope.
1. Connect the P 042 OUTPUT to the input of the oscillo 
scope (or termination), using a 50-ohm coaxial cable.
2. Turn the oscilloscope and P 042 power on and allow five
minutes warm-up time (at 25°C).
3. Set the oscilloscope controls as follows:
Volts/div 50 mV
Variable (Volts/div) Calibrated
Input Coupling Ground
4. Set the P 042 controls as follows:
OUTPUT DC LEVEL Midrange
CURRENT/DIV BALANCE Midrange
CURRENT/DIV 1 A
5. Center the trace vertically on the CRT, then switch input
coupling to DC.
. Push the thumb-controlled portion of the probe into the
locked position. When the slider is in the locked position the
shield around the transformer core is grounded, the PROBE
UNLOCKED light is extinguished, and the amplifier is ready
for operation.
7. Place the probe in the front-panel receptacle. Momen 
tarily depress the DEGAUSS lever and release. (Time required
for probe degaussing is 200 milliseconds.)
NOTE
To remove any magnetic flux present in the probe
transformer core, always degauss the probe after
Fig. 2-3. P6042 Currant Probe connecte to Type 106 Square-Wave Generator output.
2-3

Operating Instructions — Type P6042
initial turn-on and after making current measure 
ments in excess of the dynamic range of the instru 
ment. To degauss, place the probe in the front 
panel receptacle and press the DEGAUSS lever.
8. Adjust OUTPUT DC LEVEL to center the trace vertically
on the CRT.
9. Set the CURRENT/DIV switch to the suitable position for
the measurement to be made and again degauss the probe.
TO. Adjust CURRENT/DIV BALANCE to center the trace
vertically on the CRT.
11. Remove the probe from the front-panel receptacle,
move the slider back, and place the probe around the con 
ductor under test. Push the slider forward into the locked
position. Figure 2-3 shows a test application, using for the
signal source the Fast Rise output of a Tektronix Type 10
Square-Wave Generator and a 50-ohm terminating current
loop (0 7-0559-00).
12. With the oscilloscope deflection factor set to 50 mV/
div, the amplitude of the current waveform may be read
directly from the front panel of the P 042.
Deflection Factor
If (because of a high-amplitude signal) an oscilloscope
deflection factor other than 50 mV/div is desired, the overall
deflection factor must be considered when measuring the
amplitude of the signal. The following is an example:
CURRENT/DIV switch setting - 1 A
Volts/div switch setting - 200 mV
Deflection of waveform - 2.5 divisions
Calculate the amplitude of the signal:
1 A
50 mV
200 mV
div
X 2.5 div ≈ 10 A
X
Groun Clip Lea s
Ground clip leads are furnished with the probe to ground
the shield at the probe end when desired. Normally the
ground lead is not used in the 1, 2, 5, and 10 mA positions
of the CURRENT/DIV switch due to undesirable chassis cur 
rents which may appear in the more sensitive positions. When
observing high frequency waveforms, use the short ground
clip lead.
Minimize Loa ing Effect
To minimize any loading effect of critical circuits clamp
the probe at the low or ground end of a component lead
wherever possible. This will minimize the voltage feed-
through.
NOTE
The P 042 Current Probe measures magnetic flux
around a conductor due to the current flow through
the conductor. This should be kept in mind when
making readings of DC current in ferrous leads
which may magnetized (such as on transistors).
This magnetic flux will cause erroneous readings
in the more sensitive positions.
Direction of Current Flow
Direction of conventional current flow, as opposed to
electron flow, is plus to minus. Conventional current flowing
in the direction of the arrow on the probe produces a posi 
tive deflection of the waveform on the CRT (see Fig. 2-4).
2-4

Type 6042
SECTION 3
CIRCUIT ESCRIPTION
Change information, if any, affecting this section is found at the rear of the manual.
In this section you will find descriptions of the circuitry
in the power supply, the current probe, and the current probe
amplifier. The amplifier is divided into three functions: low-
frequency amplification, high-frequency amplification, and
probe degaussing.
POWER SUPPLY
The power supply provides the power for the P 042 from
two regulated supplies, +1 volts and — 1 volts. Elec 
tronic regulation is used to provide stable output voltages.
Switches on the rear panel change the connections to the
primary of the transformer for 115 volts or 230 volts, as well
as for low, medium or high line.
Power is applied to the transformer primary through the
power plug (P141), the power switch (SW141) and the fuse
(F141). F142 is switched in for 230-volt operation only. The
secondary of the power transformer has two windings,
one for the +1 -volt supply, and the other for the — 1 -volt
supply. The 0-Hz line voltage is full-wave rectified by D 1 51
in the +1 -volt supply, and by D 1 71 in the — 1 -volt supply.
C 1 52 and C 1 72 provide filtering for the respective regulated
supplies.
+ 16-Volt Supply
QI 5 provides constant current for the collector of Q 1 7,
and R157 provides a small amount of feedback to null the
ripple at the output of the supply.
(A) Positive-going voltage applie to circuit un er test.
(B) Negative-going voltage applie to circuit un er test.
Fig. 3-1. The polarities of the waveform at the output terminals of the Hall evice are etermine by the irection of current flow in the
con uctor.
3-1

Circuit Description — Type P6042
Q1 7, the feedback transistor, has a zener diode in its
emitter circuit, holding the voltage at 7.5 volts. From the
voltage divider in the output (R1 4, R1 5, and R1 ), a
portion of the output voltage is applied to the base of
Q 1 7. As the output attempts to go positive, the base of
Q 1 7 also goes positive, increasing the current through QI 1 7
and thereby lowering the level at the collector due to the
increased drop across Q 1 5 . As the base of Q 1 1 lowers,
so does the emitter, lowering the current through Q 1 3, the
series regulating transistor, and bringing the voltage level
down at the output. The level at which the output stabilizes
is set by the + 1 Volts adjustment, R1 5.
— 16-Volt Supply
The — 1 -volt supply operates in a manner similar to the
+ 1 -volt supply. The ripple-free voltage required at the base
of Q175 is provided in this case by the + 1 -volt supply.
The emitter of Q 1 77 is tied to ground, causing the output to
go to — 1 volts, set by the — 1 Volts adjustment, R1 80.
As the probe is connected around the current-carrying
conductor, the spring-loaded slider, when released, positions
the movable portion of the transformer core over the station 
ary portion. When the slider is pushed forward into the lock 
ed position, pressure is applied to the movable portion of the
core, assuring positive contact between the two core pieces.
Until the slider is pushed forward into the locked position,
switching SW3, the PROBE UNLOCKED light on the front
panel (B5) remains on. When the slider is locked, the indi 
cator bulb extinguishes and the shield around the transformer
is grounded.
The Hall device, a thin rectangular sheet of semiconductor
material sandwiched in the stationary portion of the trans 
former core, carries an electric current in the direction of its
length. When the probe is subjected to a magnetic field
normal to the semiconductor sheet, a voltage is developed
at the output terminals. This resultant voltage is at right
angles both to the direction of the current and to the mag 
netic field. This "Hall Effect ” voltage is applied to the low-
frequency amplifier.
CURRENT PROBE
The P 042 Current Probe contains a stationary core around
which is wound a 50-turn secondary, a movable core which
slides over the end of the stationary core, a ground switch,
and a Hall voltage device. The insertion impedance of the
probe is typically 0.1  at 5 MHz. See Fig. 1-2 insertion
impedance vs. frequency curve.
CURRENT PROBE AMPLIFIER
Low Frequency Amplifier
With the probe connected to the conductor under test, and
with DC voltages applied to the input terminals of the Hall
device, the signal at the output terminals varies in direct
proportion with the current passing through the conductor
Fig. 3-2. Ml 8, a ifferential amplifier integrate circuit.
3-2

Circuit Description — Type P6042
under test. The low-frequency waveforms at the two output
terminals of the Hall device are equal in amplitude an d op 
posite in polarity. The peak-to-peak difference of the two
waveforms is determined by the amount of current passing
through the conductor, and the polarity is determined by the
direction of current flow. See Fig. 3-1.
The components on the decoupling board (C5, R5, C , C9,
LRZ, and LR8), located at the input of the amplifier, form a
low-pass filter to isolate the cable from the amplifier system.
R 10 and R14, in series with the inputs of the Hall device, are
factory-selected according to the input resistance of the de 
vice to allow a current of approximately 20 mA. As the
temperature in the Hall device varies, the voltage drop across
the input terminals changes. The temperature compensation
network (R 11 , R12, and R13), applies a portion of the Hall
device input voltage to the output, reducing the drift caused
by temperature change. The output signals from the Hall de 
vice are applied to pins 2 and 10 of M18, a differential ampli 
fier circuit. See Fig. 3-2.
Pins 1, 5, and 11 of the integrated circuit are connected to
the CURRENT/DIV BALANCE control through R1 and R17.
This balance network is adjusted for zero volts at connector
J59 with no signal applied to the probe. The Hall Band 
width potentiometer, R18, and a factory-selected capacitor,
C 1 8, connected to pins 3 and 9 of the integrated circuit, pro 
vide the bandwidth adjustment for the low frequency ampli 
fier.
Q22 and Q24 reduce the voltage level at the output of the
integrated circuit, which is near one-half the supply voltage
for the following stage. The voltage gain of this stage is
adjusted by the Loop Gain potentiometer, R24.
Q42, Q44, Q45, Q51, Q53 and Q54 form a current ampli 
fier. Q42 and Q51 provide constant current for Q44 and Q53.
Q44 and Q53 are the drivers for Q45 and Q54, respectively.
Q45 or Q54, depending upon the polarity of the signal at the
collector of Q29, provide the current path through the 50-
turn secondary winding in the probe and through the attenu 
ator. When the signal at the collector of Q29 is negative,
Q44 increases conduction which lowers the base voltage of
Q45 and turns it off. Q53 reduces conduction, causing an
electron flow from — 1 V through Q54, which is turned
on, through the probe secondary and the attenuator to
ground. As the collector of Q29 goes positive, current through
Q53 increases, causing an electron flow from ground through
the attenuator, through the 50-turn secondary, and through
Q45 to +1 V. Q44-Q45 and Q53-Q54 are thermally cou 
pled to hold the voltage between the base of the driver and
the output of the stage constant. This prevents thermal run 
away. R49 and C49 provide stabilization for the output to
prevent oscillation.
The CURRENT/DIV switch provides attenuation of the
signal in a 1,2 and 5 sequence up to 1000 times attenuation
in the 1 A position. In all positions of the CURRENT/DIV
switch, the attenuator and R81 provide 50 ohms input to
the high-frequency amplifier. In the 1 mA and 2 mA posi 
tions of the CURRENT/DIV switch the collector of Q29 is
limited to + or — 0.5 volts by D39 or D37, respectively.
The current from the DC amplifier through the coil of the
probe transformer causes a flux in the core equal and op 
posite to the flux generated by the signal being measured.
This gives a resultant zero flux in the core. This feedback
system permits the Hall element and ferrite core to operate
at very low flux densities, providing excellent sensitivity and
linearity.
High Frequency Amplifier
The Attenuator Balance, R84, is adjusted for zero volts at
the base of Q87 with J80 disconnected. Q87, an emitter fol 
lower the rm ally coupled to Q9 , stabilizes the current flowing
through Q9 at various temperatures. Q9 , Q 1 13, and Q 1 21
make up a complementary feedback amplifier. The gain
of the amplifier is set by the ratio of R9 to R107 and R108.
High-frequency waveform compensation is provided by the
peaking network paralleled with the gain-setting resistors.
The DC level at the output of the amplifier is set internally
by the Output DC Level Range control, R93, and by the
front-panel OUTPUT DC LEVEL, R91. Q 1 13 is biased at its
maximum power point for a minimum temperature coefficient.
When the probe is unlocked (SW3 grounded) D 1 28 con 
ducts, bringing the base of Q 1 23 up and turning the transis 
tor on. This latches up the output of the high-frequency
amplifier and prevents any display.
Fig. 3-3. P6042 amplifier operation.
3-3

Circuit Description — Type P6042
Amplifier Operation
When the current waveform in the conductor under test
(see Fig. 3-3A) is applied to the transformer core in the probe,
the signal is seen at the input of the low-frequency amplifier
(through the Hall device) and at the input of the high-fre 
quency amplifier (through the secondary winding in the
probe). The low-frequency or DC information from the Hall
device is amplified and applied to the input of the high fre 
quency amplifier (see Fig. 3-3B). The high-frequency infor 
mation applied to the amplifier (see Fig. 3-3C) combines
with the low-frequency information, producing the resultant
waveform (see Fig. 3-3D) at the output, an accurate repre 
sentation of the original signal.
The portion of the signal amplified by each of the two
stages depends upon the frequency of the signal being meas
ured. If the signal is near DC, the output of the low-frequency
amplifier closely resembles the original signal. Conversely
with higher frequency signals, only the DC level is seen
by the low-frequency amplifier.
Probe Degaussing
Whenever a magnetic field is applied to the transformer
core in the probe with the system turned off, or if a current
beyond the maximum specified level is applied, the probe
may be magnetized. A portion of this magnetic flux is likely
to remain in the current probe core, causing erroneous meas 
urements. To remove this flux, a degauss circuit (Q73 and
Q79) is provided. With the probe inserted in the front-panel
receptacle, SW70 closes and allows operation of the degauss
circuit. When the DEGAUSS lever is depressed, the 50-turn
secondary is removed from the amplifier and connected to the
output of the degauss oscillator Q73 and Q79. C 5 (charged
to +1 volts) is applied to the circuit, which oscillates at
approixmately 10 kilohertz. As C 5 discharges, the ampli 
tude of the oscillator signal decays exponentially, degaussing
the probe core. The time required for probe degaussing
is about 200 milliseconds. See Fig. 3-4.
Q31, which is normally off, is associated with the degauss
circuit. To successfully degauss the probe core, the junction
of R4 and R5 must be near zero volts when the DEGAUSS
lever is released. When the DEGAUSS lever is depressed
Q31 turns on, bringing the bases of Q44, Q53 and the out 
put of the current amplifier near zero volts. When the
DEGAUSS lever is released, C33 discharges and slowly
turns Q31 off, thereby preventing a transient from being
applied to the 50-turn coil by the current amplifier.
3-4

TyP e P6042
SECTION 4
MAINTENANCE
Change information, if any, affecting this section is found at the rear of the manual.
Intro uction
This section of the manual presents preventive maintenance
troubleshooting, and corrective maintenance information for
servicing and repairing the P 042. If trouble occurs in the
probe or amplifier, corrective maintenance should be per 
formed immediately to avoid additional damage and to re 
store the instrument to proper operation.
PREVENTIVE MAINTENANCE
Preventive maintenance consists of cleaning, visual inspec 
tion, and recalibration. The conditions of the environment
in which the instrument is used will determine the need
for maintenance. The probe should be taken apart and
cleaned periodically.
Probe Disassembly
2. Remove the two screws from the bottom of the probe
body and move the strain relief boot back over the cable.
3. While holding the probe horizontally with the slider
up, lift the top half of the probe body up and slide it off
the end of the probe. Be careful that the metal ball does
not fall out of the hole in the top of the slider.
4. Remove the metal ball from the slider.
5. With a small screwdriver, lift the spring retainer and
spring out of the holder and remove. (Lift the back of the
slider slightly.)
. Lay the probe on its side and remove the slide assembly.
When removing the movable portion of the transformer core
and the contact from the slider, note the position of the con 
tact spring. Neither the spring nor the switch contacts are
removable.
7. Remove the spring holder from the bottom half of the
probe body. When removing the stationary portion of the
transformer core, note the position of the pins on the 8-pin
plug. If necessary, unsolder the connections to the bottom
half of the probe body. The probe is shown disassembled
in Fig. 4-1.
1. Move the probe slider to the open position.
Fig. 4*1. Disassemble P6042 Probe.
4-1

Maintenance — Type P6042
Fig. 4-2. Locations of components mounte on circuit boar s. (A) Amplifier circuit boar (B) Decoupling circuit boar .
4-2

Maintenance — Type P6042
Probe Cleaning
Use a soft bristle brush to dislodge the dust and wipe
clean with a lint-free cloth. If a persistent coating of dirt
remains, it can be removed by washing the probe parts in
warm water with some liquid detergent added. (Unsolder
the cable from the connections on the bottom half of the
probe before washing.) After drying, apply a coating of
Lubriplate or similar lubricant to the moving parts of the
probe.
NOTE
Do not use any organic solvents to clean the probe.
Probe Assembly
1. If unsoldered, resolder the cable to the bottom half of
the probe.
2. Insert the pins of the stationary portion of the trans 
former core into the receptacle on the end of the cable and
place the core in position. Replace the spring holder.
3. Replace the contact spring and the movable portion of
the core in the slider. Place the spring and retainer in posi 
tion on the spring guide.
4. Insert the tip of the slider into the slot provided at the
front of the probe and bring the two pieces together. Be
sure that the slider switch contacts go on the inside of the
stationary contacts. As the two pieces are brought together,
push the spring retainer into position in the holder.
5. Hold the probe with the slider up and place the metal
ball in the hole in the slider.
. Replace the top half of the probe, the strain relief
boot, and the two screws.
Amplifier Cabinet Removal
In order to gain access to the circuitry in the amplifier for
calibration or troubleshooting, it is necessary to remove
the instrument chassis from the cabinet. To remove the cabi 
net, disconnect the power plug and loosen the thumb-screw
at the lower left corner of the front panel. Reach to the
back of the instrument and push the chassis out through the
front of the cabinet. Pull the power cord through the cabinet.
Visual Inspection
The P 042 amplifier should be inspected occasionally for
possible defects such as damaged parts. The procedures for
correcting most visible defects are obvious, but particular
care should be taken if heat-damaged components are found.
Overheating usually indicates other trouble in the instrument.
Therefore, it is important that the cause of the overheating
be found and corrected to prevent a recurrence of the
damage.
CAUTION
Before removing the shield from the bottom of the
chassis, disconnect the power cord from the power
source to avoid a short-circuit with the contacts on
the POWER switch.
Recalibration
To assure the correct and accurate operation of the P 042
Probe, it should be checked after each 1000 hours of opera 
tion and recalibrated if necessary. A complete recalibration
should be performed at least once every six months, even
if the probe is used only intermittently. Minor troubles that
may not be apparent during normal use may be detected
during the calibration procedure.
TROUBLESHOOTING
The following information is provided to aid in locating
and correcting trouble in the P 042 Probe. Information found
in the Circuit Description, Performance Check, and Calibra 
tion will also be helpful when attempting to troubleshoot the
instrument.
Troubleshooting Ai s
Diagram. The circuit diagram of the P 042 Probe is given
at the rear of this manual. Circuit numbers and electrical
values of the components are show on the diagram. Portions
of the circuitry that are mounted on circuit boards are out 
lined in dashed lines.
Circuit Boar Illustrations. Many of the electrical com 
ponents in the P 042 amplifier are mounted on circuit boards.
To aid in locating components and identifying connections
to the circuit boards, Fig. 4-2 shows the physical locations of
all components mounted on the boards and the color code
of the connecting wires.
Troubleshooting Proce ure
The following general procedure is suggested for isolation
of a malfunction in the probe circuitry.
Check Associate Equipment. If trouble occurs in the
P 042, disconnect the probe from the oscilloscope input and
check that the oscilloscope is operating properly without
the probe.
Check Voltages. If the associated equipment appears
to be operating normally, check through the circuitry for
correct operating voltages as given on the schematic dia 
gram. The DC voltages are obtained with no signal ap 
plied to the probe and with the OUTPUT DC LEVEL con 
trol set for zero volts. Place the probe in the front-panel
receptacle while measuring voltages and degauss periodi 
cally.
Check Circuit Calibration. If the preceding voltage
checks indicate improper operation of a particular part of
the circuitry, check the calibration of that circuit according
to the procedure given in the Calibration section of this
manual. Improper setting of a calibration adjustment can
often cause incorrect operation of a circuit, and thus of
subsequent circuits.
Check Semicon uctors. Most circuit problems result from
the failure of a transistor or diode due to normal aging and
use. The recommended method of checking transistors in
4-3

Maintenance — Type P6042
Fig. 4-3. Locations of color co e of wiring connections. (A) Amplifier circuit boar (B) Decoupling circuit boar .
4-4