AEMC 1000N Use and care manual

Rev. 8 3/04
MEGOHMMETER
MODEL 1000N
(CATALOG# 185.100)
REPAIR AND CALIBRATION MANUAL

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TABLE OF CONTENTS
Repair and Technical Services....................................................................................... 3
Introduction..................................................................................................................... 4
Specific Features............................................................................................................ 4
Principal Characteristics ................................................................................................. 4
Specifications ..................................................................................................................6
Operation........................................................................................................................ 7
Calibration .................................................................................................................... 11
Taking the Instrument Apart ......................................................................................... 14
Troubleshooting............................................................................................................ 17
Summary of Malfunctions ............................................................................................. 20
Component Parts List ................................................................................................... 21
Mechanical Parts List ................................................................................................... 26
Test Points ................................................................................................................... 28
Power Board Schematic and Specifications ................................................................. 29
Main Board ................................................................................................................... 30
Measure Board............................................................................................................. 31
High Voltage Board ...................................................................................................... 32
Schematics........................................................................................................... 33 & 34
Revision Description Date Approved
1 Updated Specs May 21, 1996 JPM
2 Updated Specs July 17, 1997 JPM
3 Updated Specs September 23, 1998 JPM
4 Updated Specs June 8, 1999 JPM
5 Added Power Supply Schematic and Specs August 25, 2000 JPM
6 Added changes to schematics November 13, 2000 JPM
7 Modified Board Drawings June 7, 2002 JPM
8 Z4, Z7 and Z9 changed to OP07C March 13, 2004 JPM

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REPAIR AND CALIBRATION
NOTE: Any attempts to repair and/or maintain this instrument, other than replacement of
fuses and batteries, voids the warranty of the instrument. The presence of high
voltages at certain locations requires servicing of this instrument by qualified
personnel. It is recommended that the instrument be sent to an authorized service
center.
To guarantee that your instrument complies with the factory specifications, we recommend
that the unit be submitted to our factory service center at one year intervals for
recalibration, or as required by other standards.
For instrument repair and/or calibration, please call our factory at (800) 945-AEMC.
CHAUVIN ARNOUX®, Inc.
d.b.a. AEMC®Instruments
15 Faraday Drive • Dover, NH 03820 USA
[phone] • [phone] • Fax: [phone]
(Or contact your authorized distributor.) Estimates for repairs, normal recalibration, and
calibration traceable to N.I.S.T. are available.
All customers must call for an authorization number before returning any instrument.
TECHNICAL AND SALES ASSISTANCE
If you are experiencing any technical problems, or require any assistance with the proper
use or application of this instrument, please call our technical hotline:
CHAUVIN ARNOUX®, Inc.
d.b.a. AEMC®Instruments
[phone] • [phone] • Fax: [phone]
www.aemc.com

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INTRODUCTION
The Model 1000N Megohmmeter is a portable instrument which is essentially intended for
performing insulation tests upon various components of electrical systems and equipment.
The instrument allows completion of measurements according to multiple voltage levels (step
voltage method), making it possible for the user to evaluate insulation quality and to plan
preventive maintenance accordingly (especially for motors).
SPECIFIC FEATURES:
• If a linear response were to be adopted for resistance and conductance, a high number of
scales would be required on account of the extent of the measuring range which must be cover
in practice, from 1 MΩto 1000 GΩ.
The use of logarithmic response circuitry reduces the number of scales to two. Each scale
covering three decades. The accuracy is typically on the order of ± 5% over the entire range.
• Selection of the test voltages does not cause the measuring range to change. It is very easy to
determine the influence of voltage upon insulation.
• An additional range is provided to cover from 1 kΩto 1 MΩ. This range uses a constant current
source (1 mA) to perform the measurement. The maximum open voltage is limited to
approximately 1100 V.
• A voltmeter range covering from 0 to 600 V AC or DC allows the user to verify whether or not
the circuit where the insulation must be tested is energized.
• Insulation testing and voltmeter functions are accompanied by a continuity test range from 0.1Ω
to 100Ω. The logarithmic scale provides excellent accuracy between 0.1Ωto 1Ω. A fuse is used
for overload protection in case of incorrect measuring procedures.
PRINCIPAL FEATURES:
Insulation Testing:
• Test voltages - The rotary selector switch allows the choice of five voltages:
50 V, 100 V, 250 V, 500 V, 1000 V.
• Ranges for each test voltage
MΩ: 1 MΩto 1000 MΩ(typical accuracy: ± 5% of reading, max: ± 10% of reading)
GΩ: 1 GΩto 1000 GΩ(typical accuracy: ± 5% of reading, max: ± 10% of reading)
KΩ: 1 KΩto 1000 KΩ(typical accuracy: ± 5% of reading, max: ± 10% of reading)
NOTE: From 100 GΩto 1000 GΩ, the typical accuracy is ± 10% and max. is ± 20% of
reading on the 50 V range.

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Continuity Testing:
0.1Ωto 100Ω(typical accuracy: ± 5% of reading, max: ± 10% of reading or 5 mΩ)
The logarithmic scale is the same for the Ωand KΩrange. The 0.1Ωis calibrated at the output
terminal of the instrument. You need to subtract the resistance value of the leads from your
measurement if you need the accuracy under 10Ωs.
DC or AC Voltage Measurements:
In order to ensure that the system under test is not energized, the instrument functions as a
voltmeter as soon as it is connected, provided the push-to-measure button has not yet been
pressed. This is the case for every range selected.
Scale: 0 to 600V AC or DC: accuracy: 3% of full scale
Time Constant:
K M G
Charging time (R reading) x (C reading) 0.04 Sec / µF 4 Sec / µF
Discharging time 0.1 Sec / µF or 0.3 Sec / µF to decrease below 50 V
Safety Features:
• This instrument is capable of withstanding overloads of up to 600 V for any selected function.
• The continuity range is protected by a fuse inserted in the "G" (Guard) terminal and is
accessible when the battery compartment is removed.
Influence:
• Temperature: Twice the accuracy per 10° C variation
Supply voltage: Half the accuracy for battery voltages between 9 and 13 Volts
• Humidity: No significant influence up to 40° C and up to 70% relative humidity
Dielectric Strength:
• 4000V RMS at 50 Hz for 1 minute between all input terminals and any accessible metal
portions of the instrument.
• Model with AC power supply accessory: Add test at 4000V RMS at 60 Hz for 1 minute
between the AC outlet and any accessible metal portions of the instrument.

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SPECIFICATIONS:
ELECTRICAL
INSULATION TESTS
DC TEST VOLTAGE: 50, 100, 250, 500, 1000 V
MEGOHM RANGE:
For each test voltage two direct reading ranges
1 to 1000 MΩ
1 to 1000 GΩ(1,000,000 MΩ)
SHORT CIRCUIT CURRENT: 5 mA (max)
ACCURACY: 5% of reading typical
15 % of reading between 100 MΩto 1000 GΩon the
50V range
CHARGING TIME: 1000 MΩrange: 0.3 s/µF
1000 GΩrange: 4 s/µF
DISCHARGE TIME:
Automatic discharge when test button is released; 0.1
s/µF
SCALE:
Two large overlapping scales: 4.7" (119 mm) for each
range
TEST VOLTAGE GENERATION:
Solid state circuitry generating rated test voltage
across the full range
RESISTANCE TESTS
TEST CIRCUIT: Constant 1 mA DC
KILOHM RANGE: 1 to 1000 kΩ
MAXIMUM TEST VOLTAGE: 1200 V DC
ACCURACY: 5% ± 100Ωof reading typical
CONTINUITY TESTS
TEST CURRENT: Constant 10 mA DC
OHM RANGE: 0.1 to 100Ω(3Ωmidscale)
ACCURACY: 5% ± 0.05 Ωof reading typical
FUSE PROTECTION: 0.3 A high interrupting capacity
fuse
VOLTAGE TESTS (SAFETY CHECK)
VOLTAGE RANGE: 0 to 600 V DC
ACCURACY: 3% of full scale
GENERAL SPECIFICATIONS
AUDIBLE TEST SIGNAL: Ten beeps per minute for
insulation and resistance tests; continuous tone for
continuity test reading ≤200Ω
POWER SUPPLY: Eight 1.5 V "AA" alkaline batteries
(NEDA 15A). Typical battery life: 350 one-minute
tests; power consumed only when test button is
depressed; built-in battery check by green LED.
OPTION: 110/220 V selectable, 47 to 400 Hz AC
supply module
DIELETRIC TEST: 4000 V AC, 60 Hz, 1 min
METER MOVEMENT: Rugged taut band suspension
DIMENSIONS: 7.7 X 5.2 X 3.75" (196 X 132 X 95 mm)
WEIGHT: 2.2 lbs (1 kg)
TEMPERATURE RANGE: 23 to 122°F (-5 to 50°C)
CASE: High impact gray polycarbonate
TERMINALS:
Color-coded safety terminals; guard terminals
eliminates surface leakage errors
SAFETY/REFERENCE STANDARDS

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OPERATION:
a) Mode of Operation for MΩand GΩ:
An oscillator (Z1) provides a low voltage signal which is amplified by the transformer (T1) then
rectified and filtered (CR201, C201). This high DC voltage is regulated through the divider (R202
to R209) and the operational amplifier (Z4).
When the range switch is turned to select a new voltage range, the input of (Z4) is open. In
order to prevent an increase in the high voltage, two diodes (CR12 and CR13) are connected to
the + supply in order to always bring the output of Z4 to the + supply and stop the oscillation of
Z5 and the high voltage.
HV GENERATOR
LOGARITHMIC
AMPLIFIER
G
RX
Vd
Vm
CR
VHT
+-
RM
DIVIDER BRIDGE MEASURING SHUNT
RX =
()
VHT
VM 1RM, or VM VHT ∗ RM
RX
=
~
VM = K
RX
Because RM is significantly lower than RX, the portion of the curve which is used, VM
=
f(RX),
can be expressed as a function
K
R
X
.
Measurement for the MΩrange with test voltages of 50 and 100 Volts is performed by
measuring the voltage drop on the shunts R101 and R102. For test voltages of 250, 500, 1000
Volts is performed through the current shunt R102 only.
Measurement for the GΩrange is performed by measuring the voltage drop on the shunt R103.
The resulting voltage is then filtered and passed through a variable gain amplifier (Z5) then into
a logarithmic amplifier (Z4). Temperature compensation is provided to the amplifier by a
thermistor (TH1). The last amplifier (Z7) provides the current needed to drive the meter
movement G1.
A negative 4.6 Volt supply is provided by (Z3) for powering the quad amplifier (Z2).

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The beeper (BZ1) is power by the oscillator (Z8) and the transistor (Q3) every six seconds,
except for when in the ohm range where the comparator (Z2) allows the beeper to operate
continuously for resistance levels under 200Ω.
The comparator (Z2) permits the "BAT" led to turn off whenever the battery voltage is less than
9 V DC.
The resistors (R214) and (R215) allow the circuit under test to discharge when the push-to-
measure button is released.
The protection of the measuring circuit in case of a short circuit between the positive and
negative terminals is provided by the discharger (E101) for voltages exceeding 90 V.
b) Mode of Operation for KΩ
HV GENERATOR LOGARITHMIC
AMPLIFIER
G
RX
Vd Vm
VHT
+-
CONTROL SHUNT
KR
R
R104
CR
During the operation of the circuit loop, VD = cte. Therefore, a constant current flows through
(R104) and (RX). VHT varies in proportion to RX, and a resistance bridge permits bleeding of a
portion of VHT in order to perform the measurement.
VM =R
X
K
I+R104
K
I
=
CONSTAN
T
The voltage output is limited to approximately 1300 Volts when the measuring terminals are
open.

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c) Voltmeter - Mode of Operation:
When the push-to-measure button is up, the Model 1000 Megohmmeter functions as a DC or
an AC voltmeter. The input resistance is close to R214 + R215 = 90 KΩ. The voltage is
reduced by means of (R212) and (R213) and rectified by the diode (CR10) and (CR11).
R214
47 K
R215
47 K
R212
2.67 M
R213
291 K
C202
1 uF
R50 R51
G
CR10
+
-
--Positive voltage
--Positive alternation
R214
47 K
R215
47 K
R212
2.67 M
R213
291 K
C202
1 uF
R50
R51
G
CR11
+
-
--Negative voltage
--Negative alternation

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d) Ohmmeter - Mode of Operation:
CONSTANT
CURRENT
GENERATOR
(RX)
(G)
Shift from 0 to 0.1 Ohm
for Start of Scale
Measuring Amplifier
(Z5)
(R26)
The high voltage section is not used when the instrument functions as a ohmmeter.
(Q2) and (CR3) constitute a constant current generator. The current generated flows through
the resistor under test (RX). The respective voltage (VRX) is directly measured by the
amplifier (Z5).

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CALIBRATION:
Recommended Cleaning Procedures:
The exterior should be cleaned periodically with a cloth moistened with water and a mild
detergent solution. (Do not use chlorinated solvents or solvents containing hydrocarbons).
Wipe the instrument and let it dry completely before using it again.
NOTE: The adjustment procedures described below should be performed under the following
environmental conditions:
Temperature: 21°C ± 3°C
Humidity: 30 to 60% RH
Required Items:
• 1 DC power source, with adjustable voltage between 8 to 15 V (1 A Max.)
• 1 DC ammeter (minimum range: 0.5 A), with voltage drop less than 0.1 V.
• 1 Voltmeter with 20,000 cts of resolution capable of measuring at least 10 V.
Impedance ≥1 MΩ
• 1 Set of resistors 1 MΩ, 100 MΩ, 1000 MΩ, 100 GΩ, 1000 GΩ(accuracy 1% or less,
operating voltage > 1000 V).
• 1 Resistor 100 Ω/ 1%
• 1 Resistor 0.1 Ω/ 1%
• 1 AC power source, 0 to 600 V 50/60 Hz ± 1%
Calibration Procedures:
a) With the push-to-measure button disengaged, provide 600 V AC between the + terminal
(green) and the - coaxial plug. The reading must be between 582 and 618 V (± 3% fs).
Otherwise consult the troubleshooting section.
b) Remove the bottom portion of the instrument by unscrewing the two center screws when the
push-to-measure button is up, (See section B on page 13). This allows access to the
adjustment potentiometers.
IMPORTANT: This is a high precision instrument. It is very important to keep the printed circuit
boards absolutely clean. Do not touch the circuit boards with fingers and prevent
foreign substances from coming into contact with the boards.
c) Initial Conditions:
Place the potentiometer A1 to the farthest counter-clockwise position.

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d) Offset adjustment of the amplifier (Z5) when RX = ∞(open)
• Supply the Model 1000 with 10.5 V DC.
• Connect the voltmeter between the T and D solder pins (the ground connection D can be
made on the spacer of the high voltage switch.)
• Select the 250 V / MΩrange and push down the on/off switch. The beeper must "beep"
approximately every 6 seconds.
• Adjust the potentiometer A101 to obtain a reading of 0 ± 40 µV on the voltmeter.
• Select the 50 V / GΩrange and verify the reading is still 0 ± 200 µV.
• Select the 1000 V / GΩand adjust the potentiometer A103 to read 0 ± 200 µV on the
voltmeter.
NOTE: Because the two settings are highly sensitive, it is necessary to allow a few seconds
between adjustments in order to obtain a stable reading, especially for the GΩrange.
Never short circuit the terminals at this stage, a memory effect on the input capacitor may
produce an incorrect zero.
e) Adjusting the "1" point on the MΩscale:
• Select the 500 V / MΩrange and measure 1 MΩ.
• Adjust the potentiometer A4 to read "1" on the MΩscale.
f) Adjusting the "100" point on the MΩscale:
• Select the 500 V / MΩrange and measure 100 MΩ.
• Adjust the potentiometer A5 to read "100" on the MΩscale.
g) Adjusting the "1000" point on the MΩscale:
• Select the 500 V / MΩrange and measure 1000 MΩ.
• Adjust the potentiometer A102 to read "1000" on the MΩscale.
NOTE: The adjustment of the potentiometer A5 and A102 are interdependent. It is necessary to
perform these two tests until the two readings are perfect.
h) Adjusting the Ohmmeter:
• Select the 10 mA range on the instrument.
• Measure 100Ωand adjust the potentiometer A2 to read "100" on the ohms scale.
• Measure 0.1Ωand adjust A3 to read "0.1" on the ohms scale.
• During this adjustment check the reading on the voltmeter connected between the point T
and D. The value must be positive ( ≅+ 8 mV ). Otherwise, it is necessary to continue
adjusting A3.
• It is necessary to verify the linearity at several locations.
• The deviation should be less than or equal to 1 mV from the theoretical value (or 5%).
• For resistor values under 200Ωthe beeper must be "on" continuously.

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NOTE: The 0.1Ωresistor must include the value of the leads used in the calibration.
i) Adjustment of the Short Circuit Current:
• Connect an ammeter in series with the battery supply and adjust battery voltage to
9 V DC.
• Select the 1000 V / MΩrange.
• Measure RX = 1 MΩand note the power consumption on the ammeter.
• Measure RX = 0 and adjust A1 to obtain the prior current ± 20%.
• The green LED should turn off when the battery voltage drops below 9 V.
j) Select the 1000 V / GΩrange and measure RX = 1 MΩ, 10 MΩ, then 100 MΩ. The needle
must always deflect to the left side. If not, add the diodes CR14 and CR15 to the main board.
(If not already modified).
NOTE: Let the instrument set for at least one hour before testing the specification on all the
ranges. The short circuit on step “j” disturbs the offset of the amplifier especially on the 50
V / GΩrange.

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TAKING THE INSTRUMENT APART:
Necessary Tools:
• Standard screwdriver
• 30 W soldering iron
• Desoldering iron
• Phillips No 2 screwdriver
IMPORTANT: This is a high precision instrument. It is very important to keep the printed circuit
boards absolutely clean. Do not touch the circuit boards with fingers and prevent
foreign substances from coming into contact with the boards.
A) Opening the Battery Compartment:
• Be sure the push-to-measure button is up (instrument off).
• Place the instrument on the table with the front panel down and loosen the four embedded
screws holding the battery compartment closed. Pick up the instrument with one hand and
turn it over while covering the open battery compartment with the other hand. This allows the
battery pack to be removed easily. Then place the instrument back on the table with the front
panel down while holding the exposed battery pack. Be careful not to damage the battery
connector when disconnecting it.
B) Removing the Bottom Case:
• Be sure the push-to-measure button is up (instrument off).
• Place the instrument on the table with the front panel down.
• Use a screwdriver to loosen the two center screws which secure the bottom panel.
• Lift up the bottom panel and turn it upside down in order to let the two screws drop out.
• Set the bottom down and disconnect the battery connector.
• During reassembly, the same procedure should be done in reverse order.
C) Removing the Printed Circuit Board Assembly:
• The push-to-measure button must be engaged in order to lock the spring and ball mounted
within the cap.
• Set the instrument upon the table with the front panel facing downward (after removal of the
front panel). Use a Philips screwdriver to loosen the three fastening screws holding the
bottom board to the front panel.
• With a standard screwdriver, unscrew the large center screw beneath the printed circuit
assembly. Remove all the screws and desolder the wire from the green terminal. The board
assembly can now be lifted slightly to allow the desoldering of the shielded cable, its ground
connection, and the red wire from the blue terminal.
• In order to remove the set of printed boards from the case, pull the high voltage transformer
forward and tilt the boards over the table before unsoldering the two galvanometer wires.

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D) Removing the Selector Switch Rod:
• Place the top panel on the table in an upside down position.
• Remove the attachment clamp and then remove the metal washer and spring washer. Lift
up the panel in order to remove the selector switch rod.
• The same procedure should be completed in reverse during reassembly.
E) Removing the Galvanometer:
• With the case turned forward, use a Philips screwdriver to remove the two screws which
secure the galvanometer. Use two fingers to gently push aside the two splines that hold the
dial in place. Lift the galvanometer with other hand and remove it.
• The same procedure should be completed in reverse during reassembly.
WARNING: The inner portion of the transparent surface is covered by an antistatic solution. Avoid
rubbing or cleaning this part if you do not have a replacement for this solution.
F) Removing the Bottom Board (disassembling):
• The push-to-measure button must be locked into a lower position.
• With the bottom resting upon the table, unsolder the four wires coming from the high voltage
switch, then the two wires from the transformer (red and black). Remove the screw fastening
the high voltage switch (located on the high voltage board).
• Turn the instrument over and removed the seven screws which secure the bottom board.
• As you pull the high voltage push button outward, turn the bottom board in relation to the
supporting layer.
• At this point all of the components on the bottom board are accessible.
G) Removing the High Voltage Board:
• The high voltage button must be locked into a lower position.
• The bottom board must face downward, toward the table.
• Unsolder the three connecting wires between the high voltage board and the high voltage
switch. Then the two wires from the transformer (red and black).
• Remove the six fastening screws (three of these screws are secured by a flat washer and a
lock washer).
• Turn the high voltage board in relation to the supporting layer.
H) Removing the Measurement Board:
• Remove the bottom and then the high voltage board as described above.

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I) Reassembling the Printed Circuit Boards:
• In order to reassemble the printed boards, complete the previously described procedures in
reverse, but do not tighten the screws completely. Slide the rod into the selector switch
opening to ensure proper alignment of the boards. The rod must be able to turn freely without
being obstructed. Then you can tighten all the screws.
J) Removing the High Voltage Switch:
• The high voltage button must be locked into a lower position.
• Position the bottom board so that the circuits face upward.
• Use the desoldering iron to undo the eight solder points between the high voltage switch and
the bottom board.
• Turn the bottom board over and perform the same procedures described in Section H.
• During reassembly, the same procedure should be done in reverse order.
K) Reinstalling the Printed Circuit Assembly:
• The push-to-test button should be engaged.
• With the panel turned forward, place the printed circuit boards beside it. The bottom board
should face up.
• Be sure the LED is perpendicular to the printed circuit boards.
• Resolder the two galvanometers. The red wire should be connected to the positive terminal
and the green wire to the negative terminal.
• Place the printed circuit board assembly into the panel without pushing it in entirely.
• Resolder the wire for the negative terminal (white) to the bottom board, along with the
respective ground wire (yellow). Then resolder the guard terminal wire (red).
• Fully secure the bottom board with the three Philips screws and the center screw.
• Resolder the last wire (white Teflon) to the positive terminal (green).

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TROUBLESHOOTING:
Check the condition of the batteries before performing any troubleshooting procedures. The green
"BAT" light turns of whenever battery condition is lower than approx. 9 Volts (See Section A on
page 13).
While taking the instrument apart, consult the wiring diagrams and board layouts. These diagrams
indicate various testing points for the unit.
Necessary Items for Troubleshooting:
• Standard screwdriver
• 30 W soldering iron
• Philips screwdriver
• 15 V DC power supply (1 Amp)
• 5 V DC power supply (100 mA)
• 50 V/Div. oscilloscope
• Voltmeter with 10 µV resolution and a minimum input resistance of 1 MΩ
• 1 MΩresistor (voltage > 1000 V)
IMPORTANT: Because the circuits must be kept absolutely clean in order to insure the accuracy
of the instrument, careful handling is essential. The high voltage switch, the high
voltage board, and the measuring circuit should be manipulated by means of the
transformer or the printed circuit assembly.
Indications of Improper Functioning:
(1) The instrument does not function at all (no movement of the pointer; the battery light is
not lit; the beeper does not operate):
• Set the selector switch at 50 MΩ, with the push-to-measure button in a raised position.
• Open the battery compartment in the manner described in section A on page 13.
• Disconnect the battery connector.
• Test the eight 1.5 V alkaline "AA" batteries.
• If the voltage is less than 10 V, replace the batteries. Be sure to maintain the proper polarities.
• If the voltage is higher than 10 V, reconnect the battery connector.
• Measure the voltage level at the terminals for (C102). These terminals are accessible from
the battery opening.
If there is no voltage, the battery connector is not connected.
If the voltage decreases sharply, (C102) is defective.
• If the proper voltage is present in the above measurement, press the push-to-measure button.
If the voltage drops sharply, a component within the bottom board is consuming excessive
power. This will require the disassembly of the bottom circuit board. (See Section C on page
13).
• Unsolder the wires extending from the primary on the high voltage transformer.

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• Supply voltage to the circuits with a voltage level of 12 V while monitoring the current with an
ammeter connected in series. Normal consumption is typically less than 50 mA.
• Excessive power consumption may be attributed to a short circuit at (Q1), or to defects in the
integrated circuits identified as (Z1), (Z4), and (Z8). Because these circuits are situated upon
mountings, they should be disconnected one by one until proper power consumption is
obtained.
• If none of the previously cited circuits is defective, it is advisable to check the capacitors
identified as (C24) and (C25) for probable leakage or short-circuiting.
• When the proper power consumption has been obtained, check the + 5 V and the - 5 V
levels, as well as the voltage level of diode (CR1) (+ 2.5 V).
• Disconnect the power source and reconnect the primary of the transformer.
2) Checking the Zero Setting for 1000 V / GΩ:
• Reassemble the three printed circuit boards. Then fit the rod into the switch and select 250
V / MΩ.
• Supply 10.5 Volts to the instrument. Place the voltmeter between point T and point D, and
perform the calibration procedure contained in Section d on page 11.
• If the voltage at point T exceeds 0 ± 200 µV when the selector is in the 1000 MΩposition, it
will be necessary to clean all of the printed circuit boards.
• Disconnect the instrument and remove the small white push button for the high voltage
switch, the push button cap, and the respective ball bearing and spring. These components
should not be placed in the cleaning solution while the circuits are soaking. After drying,
reinstall these items within the panel and perform all of the indicated calibration
procedures. (Consult Section b on page 10)
3) The battery light is lit and the beeper operates properly but measurement is
not possible:
Select the 250 V / MΩrange and connect a voltmeter set to the 1000 Volt range to the
measuring terminals.
(a) No voltmeter movement (control component not functioning).
• The circuit boards will have to be removed.
• Place the circuit boards upon the respective supporting layer (transformer facing up) and fit
the rod into the switch. Then select the 250 V / MΩrange.
• Supply 12 Volts to the circuit and verify the supply and reference voltage levels.
It is possible to check the open loop control sequence by adopting the following precautions.
• Open the loop at the point identified as (h) on the high voltage board. Position the high
voltage board switch between the 50 V and 100 V plugs. A finite gain should be established
for the control loop by placing a resistor which can provide a sufficient number of KΩ
between the lugs identified as (2) and (3) within (Z1).
• The control loop should be placed in operation by supplying a voltage level of + 5 V (to
start from zero) to approximately + 2.5 V at point (h). This voltage level corresponds to the
theoretical control point.

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• Check the test points identified as (4), (5), (6), and (8).
• Proper functioning at point (6): Check (T1), (CR201), and (C201).
• Proper functioning at point (5), but not at point (6): Check (Q1) and (CR2).
• No oscillation at point (5): Check the voltage level at the lug identified as (1) on (Z1).
• Voltage ≈2.5 V: (Z1) is defective.
• Voltage level not equal to 2.5 V: Check (Z4) or (CR5) and replace defective component.
Proceed in accordance to the description of removal of printed circuit boards on pg. 13.
• Replace the circuit boards and proceed with verification of zero setting for 1000V / MΩ.
• Remove the bottom circuit board in order to gain access to the components.
• After reassembling the circuit board, complete the procedures in Section d on pg 11.
(b) The voltmeter reading is 250V (high voltage available, but measuring circuit is not
functioning):
• Check the fuse (F101, 0.315 A) that is accessible after removing the battery
compartment cover. (See Section A, on page 13).
• If the fuse is defective, it must be replaced.
• If the fuse is not defective, it is necessary to remove the bottom panel.
• Connect the voltmeter between the locations identified as T and D (an identical
grounding location can be selected on the binding posts for the high voltage switch), and
set the voltmeter at 250 V / MΩ. When the button is engaged, the voltmeter reading
should be approximately 4 V when resistance of 1 MΩis being measured.
• Voltage level not appropriate: check (Z5) or (C103).
• Appropriate voltage level: Remove printed circuit boards (Section C, page 13) and use an
ohmmeter to determine if the circuit boards are disconnected. If disconnected, reconnect
the boards.
• Place the circuit board assembly upon the supporting layer and move the switch to 250 V
/ MΩ. Then it is necessary to connect a 1 MΩresistor to the measuring output wires by
soldering. Supply power to the boards with a voltage level of 12 V. The voltage at point T
should be approximately 4 V. The output voltage for (Z6) (test point 11) should be
approximately 50.7 mV. Otherwise, (Z6) is defective. The output voltage for (Z7) (test
point 12) should be close to zero. Otherwise (Z7) is defective.

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4/21/2005
Summary of Malfunctions:
• Control functions begin at over voltage level between two steps on the selector switch:
Leakage from (CR5), (Z4), and (CR6), towards (Z1).
• Adjustment of the short-circuit current: Transformer (T1) - (Z1) not operable.
• Impossible to obtain "0" on the MΩand GΩscales: The connecting layer has been cut at
(A101), (A103), or (Z5).
• Incorrect zero position for 1000 V / GΩ: The circuits are not clean, or there is insufficient
protection for selector rod circuits. No contact with small protective strip: (C103) is defective.
• Incorrect KΩreadings: (Z2).
• Incorrect voltage readings: (R212). Unsuitable power consumption levels for printed circuit
assembly (I = 100 A for 600 V point).
• Defective functioning of beeper: (Z8), (Q3), beeper.
• Battery light does not function: (Z2c), (CR9).
See Back of Manual for Schematics