AT&T M9B User guide

TCI Library https://www.telephonecollectors.info/
BELL SYSTEM PRACTICES
Plant Series SECTION 100-513-101
Issue 1, April, 1946
AT&TCo Standard
M9B METER
(PORTABLEVOLT-OHM-MILLIAMMETER
DESCRIPTIONAND APPLICATION
CONTENTS
1. GENERAL
.
....
2. CIRCUITANDEQUIPMENTFEATURES .
.
(A) M9BMeter. ...
.......
(B) Test Leads, Carrying Strap, and
Carrying Case ..
....
3. OPERATION, .
....
(A) Precautions
... .
(B) Preparation.
... ....
(C) Scales .
. ......
(D) Voltage Measurements
....
(E) Current Measurements
(F) Resistance Measurements
.
(G) Capacitance Measurements
4. MAINTENANCE.
...........
(A) Voltage Accuracy .
.
(B) Battery Replacement .....
.
5, REPAIR .........
.....
(A)
General
(B) Meter Unit .
. . . . ..
(C) Meter Glass and Zero Corrector
(D) Pin Jacks •
6. REPLACEMENTPARTS
1. GENERAL
.
.
.
.
.
PAGE
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2
2
3
4
4
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5
5
5
6
8
8
c
.
9
9
10
10
11
12
1,01 This Section describes the Western Elec-
tric CompanyM9BMeter (portable volt-
ohm-milliammeter), includes instructions for
its use and methods for replacement of parts.
The information . is also generally applicable
to the D-166852 Meter.
1,02 The M9BMeter is a small portable multi-
meter designed for general maintenance
use for the measurement of a-c and d-c volt-
ages, d-c current, and resistance, Five volt-
age scale ranges are provided, both a-c and d-'c,
from 0-3 to 0-300 volts, with a sensitivity of
2000 ohms per volt on all scales. Three d-c
current ranges are provided from 0-150 milli-
amperes to 0-15 amperes, and four resistance
measuring scale ranges from 0-1000 ohms to
0-1,000,000 ohms,
1.03 A special double-pointer meter movement
provides unusual legibility of scales;
the linear voltage and current scale markings
are
grouped in the upper semicircle of the me-
ter fa~e, and the nonlinear resistance scale
is located under the pointer sweep on the lower
semicircle of the meter face, The wide angle
sweep (150 degrees) of the pointer adds to the
legibilityof the scales. A nonglare, hardened
glass window is used. All circuit connections
are made to positive contact pin jacks, Fig, 1
shows a face view of the M9BMeter.
Fig. 1 - M9BMeter - !''ace View
1.04 The M9BMeter is furnished with a pair of
KS-9290 test pick leads• a pair of KS-9291
test clip leads and a KS-9308 carrying strap.
A 4-1/2-volt battery (par, 2.08) is required for
use in the meter. The meter is equipped with
"D" loops for attaching a neck carrying strap
(KS-9308), A fibre carrying case (KS-9307) is
available for carrying the meter and test leads.
(See Figs. 2 and 3.) The M9BMeter is
similar
to the Western Electric Company D-166852 Vol~-
ohm-milliammeter which was recently developed
for maintenance use with carrier, central
office~ and telegraph equipments.
Copyright, 1946
1
by American Telephone and Telegraph Company
Printed in U.S. A,
Page
1

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SECTION 100-513-101
2, CIRCUITANDEQUIPMENTFEATURES
(A) M9BMeter
2,01 A schematic of the M9BMeter is shown in
Fig, 4, The scale ranges provided are
as follows:
Voltmeter
Ranges
A-C or D-C
(2000 Ohms
Per Volt)
0-3 volts
0-15 volts
0-30 volts
0-150 volts
0-300 volts
Ammeter
Ranges
D-C Only
0-150 milliamp,
0-3 amp.
0-]6 amp.
Ohmmeter
Ranges
0-1000 ohms
0-10,000 ohms
0-100,000 ohms
0-),,000,000ohms
The accuracy of the meter is _:!:2per cent. of
full scale for d-c and _:5 per cent, of full
scale fora-c measurements; for resistance meas-
urements, the accuracy is _:!:2per cent. at one-
half the pointer travel, i.e., at "4o" on the
OHMSscale,
2.02 The meter movement is of a relatively
sensitive type, requiring 100 microamperes
of current to obtain full-scale deflection,and
is combined with suitable series and shunting
resistances to provide for the direct current,
the a-c and d-c voltage, and the resistance
ranges tabulated in Paragraph 2 ,01. In the
voltmeter condition, on all scales, a-c and
d-c, the internal resistance (sensitivity) of
the meter is 2000 ohms per volt,
2,03 The dial (Fig. 5) is circular, with the
current and voltage scales on the upper
half of the dial and the nonlinear resistance
scale on the lower half, The double-ended
pointer is pivoted at the center. One end of
the pointer travels over the upper scales; the
other end of the pointer sweeps over the lower
scale. This provides a complete separation of
the nonuniform resistance measuring scale from
the markings for the current and voltage meas-
uring scales, which makes the scales easier
to read than the conventional type meter which
has all scales grouped under one pointer. The
pointer swing is from zero on the left, to full
scale on the right, on all scales, Instead of
the conventional arc of 90 degrees, the point-
ers swing through a 150-degree arc from zero to
full-scale readings. The outside scales are
approximately 2-374" long.
2,04 A face view of the volt-ohm-milliammeter
is shown in Fig, 1. All the connections
to the meter are made by means of pin ~acks,
Connections for resistance measurements (X and
R jacks) are on the left side of the panel;
those for voltage measurements (V jacks) are
located on the ril$ht side of the :{lanel and cur-
rent measuring (A and MAjacks) are located
along the lower part of the panel.
Page 2
2,05 A copper-oxide rectifier in the meter
provides means for using the d-c meter
movement for measuring a-c voltage, Operation
of the AC-DCtoggle switch at the right of the
meter dial cuts the rectifier into the circuit
for a-c voltage measurements or eliminates it
for all d-c measurements, including resistance.
2.06 Two toggle switches located to the right
VM of the meter and designated AC-DC, and
AM- RES, together set up the internal connec-
tions which are required for each type of use;
that is, as either an a-c or d-c voltmeter, as
a d-c a:mmeter, or as a resistance measuring
device.
2,07 A quick-acting push-to-read switch (with
its push-button marked PRESS) is provided
to connect the meter movement across the in-
ternal d-c measuring shunts which are associ-
ated with the -A, 15A, 3A,and 15011A jacks.
The meter movement is only connected to read
current while this switch is depressed,
,.,
Fig. 2 - 119BMeter in Carrying Case
Open Cover

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Fig, 3 - KS-9307 Carrying Case with KS-93()8
Carrying Strap
2.08 A 4-1/2-volt battery is required for use
in the meter, The battery mounts in a
bracket inside the meter case, Any one of the
following batteries may be used:
Bright Star 03-17s
Eveready 781
Burgess 5360
Ray-0-Vac 531R
Bond 317
2,09 The knob BATTERYADJUS1'MENTcontrols a
rheostat which adjusts the "zero" setting
portion of the resistance measuring circuit,
This setting varies with the voltage and condi-
tion of the 4-1/2-volt dry cell battery,
ISS 1, SECTION 100-513-101
(B) Test Leads, Carrying Strap, and Carrying
Case
2,10 The tes~ leads supplied with . the meter
are equipped with pin terminals at one
end for connection to the meter jacks, One
pair of test leads (KS-9291) is equipped at
the other end with test picks, the other pair
(KS-9290) with test clips, The test picks are
7-1/2" long and consist of a slender hard rub-
ber handle with a pick extending approximately
1/2 11 from the end, The test clips are narrow,
alligator-type clips.
2,11 The KS-9308 carrying strap is available
for use with the M9BMeter. This strap
(Figs, 2 and 3) is equipped on each end with a
harness snap and is adjustable as to length by
means of a sliding buckle, The strap is in-
tended to attach to the metal 11
D11 loop on the
sides of the instrument, and to be used as a
neck strap to support the meter so
as
to leave
both hands of the tester free for making test
connectionsJ or the strap may be attached to
the KS-9307 carrying
case
and used in the same
way,
2,12 The Ks-9307 carrying case maybe obtained
for use with this meter, This fibre case
(Figs. 2 and 3) i,s arranged with
a
hinged top,
inside of which
a
snap-fastened fabric flap
~rovides a place for storing the test leads
(Fig, 2), There is a "D" ring on each side of
the case to which the KS-9308 carrying strap
tnay be attached, The
case
is so designed that
Bl
x~•l•l1----..----..-----------------t------------l.'O -v
4.!>V,
32 .!I
>--- .....
R4
299-
2994 ...
R6
2000 ...
30,000'"'
BATTERY
ADJUSTMENT
Pl
R20
492 ...
-A
Rl7
0
I:.A
Rl8
0
3A
Vt.A
AM
Fig, 4 - Schematic Diagram of M9BMeter aircuit
4885"'
24,000-
120,000""'
150,000
Page 3

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SECTION.100-513-101
when the lid is open the meter can be used with-
out removing it from the case. A simple clamp-
ing device holds the meter securely in posi-
tion in the case, cushioned between sponge rub-
ber blocks on sides, end, and bottom, There
is room for two spare dry batteries inside the
carrying case, in the space between the hinged
side of the case and the meter; one may be
placed on each side of the meter clamping de-
vice,
2,13 The dimensions and weights of the H9B
Meter and associated equipment are as
follows:
Dimensions pn.) Wt,
Name Length Width Depth Lbs,
M9BMeter 8 4-1/4 3-1/2 3.25
KS-9290 Test Leads
(pair) 50 0.18
(ea)
KS-9291
(pair) Test Leads 50
(ea) 0.06
KS-9308 Carrying 4o 1 0.18
Strap
KS-9307 Carrying 8-1/2 6
6
3.4
Case
3. OPERATION
(A) Precautions
3.01 In order to avoid damage to the meter,
the following precautions should be ob-
served, Do not connect resistance measuring
jacks
(X
and
R)
to a circuit which includes a
source of either d-c or a-c power, since it
may damage the meter movement and t he meter
resistances, This is particularly important
with regard to a-c power, because the alternat-
ing current entering the meter throu~h the re-
sistance measuring jacks (X .and R) will not
give a meter deflection and therefore might
destroy either the meter coil or a resistance
without giving
a
warning indication on the me-
ter. Do not connect the current measuring
jacks (-A, 15A,
3A,
and 150MA) to a circuit in
which the current is greater than 15 amperes
d-c; do·not connect into an a-c circuit,
(B) Preparation
3,02 Before making direct current or a-c or d-c
voltage measurements, check that the upper
pointer of the meter lines up exactly with the
zero mark of the upper scales, (which also sets
the lower pointer at the (infinity) nark of the
resistance measuring scale), The zero posi~ion
of the pointers can be adjusted by turnin g the
slotted bakelite button in the center of the
meter glass with a screwdriver or small coin.
(C) Scales
3.03 Two scales, inner and outer, appear on
the top half of the meter face. A single
scale for resistance measuring, calibrated in
ohms is on the lower half, Fi g, 5 shows the
meter scales in detail.
3.04 The inner scale (with red markings) on the
upper half of the dial is for readin g a-c
voltages in the 0-3-volt range. This separate
scale is necessarv because a nonuniform move-
ment of the meter.pointer is produced when a-c
voltage within this low range is measured,
3,05 The outer scale is used for all other
voltage measure ;nents both a-c and d-c
and for direct-current measurements, It haa
75 equal divisions with every fifth division
a long mark, It is marked with black figures
at each 25 divisions, as follows:
50
100 100
200 150
300
The outer scale divisions and markings have
the fol lowing values for current and voltage
measurements:
Current or Voltage Value Scale Value
for Top Pointer at Each Division
When Connected 50 100 150 Short Long
Measuring to Jacks 100 200 300 Lines Lines
Direct -A and 150MA 0.050 amp. 0.100 amp, 0.150 amp, 0.002 amp, 0.010 amp,
Curren+, -A and 3A 1.0 amp, 2,0 amp, 3.0 amp. o.o4 amp, 0.2 amp,
-A and 15A 5.0 amp. 10.0 amp. 15.0 amp, 0.2 amp. 1.0 amp.
Voltage*
-V
and
-,v
1 volt 2 volts 3 volts 0,04 volt 0.2 volt
D-C Only
-V
and 15V 5 volts 10 volts 15 volts 0.2 volt 1 volt
Voltage -V and 30v 10 volts 20 volts 30 volts o.4 volt 2 volts
A-C or -V and 150v 50 volts 100 volts 150 volts 2,0 volts 10 volts
D-C -V and 300v 100 volts 200 volts 300 volts 4,o volts 20 volts
Voltage• -V and
,v
Use top pointer and RED scale
A-C Only
* For measuring a-o voltages when
jacks, see Paragraph 3.04. connected to the -V and "3V
Page
4

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Fig. 5 - M9B!1eter - Face View
3.06 The resistance scale (lower half of the
dial (Fig. 5)) is read directly in ohms
if the test cords are connected to X and R
(0-1000-ohm scale). If the test cords are con-
nected at X and RxlO, the scale reading should
be multiplied by ten; if the connections are at
X and RxlOO multiply the scale reading by 100;
if connections are at X and RxlOOO, multiply
the scale reading by 1000.
(D) Voltage Measurements
3.07 In measuring d-c voltage, set the upper
toggle switch at its DC position; in
measuring a-c voltage, set this switch at its
AC position. Set the lower toggle switch at
its X}1position. Make connections to the -V
pin Jack and to the 300v, 150v, 30v, 15v, or
Yi pin jack depending on the amount of voltage
to be measured. In measuring d-c voltage con-
nect the -V pin jack to the negative side of
the circuit being checked.
(E) Current Measurements
3.08 Direct current onlt can be measured.
When direct curren is to be measured
set the upper toggle swit.ch at its DC position
and the lower toggle switch at its mposition,
ISS 1, SECTION 100-513-101
Connect the negative side of the circuit to the
-A pin jack and the positive side of the cir-
cuit to the 15A, 3A,or 150MAjack dependint on
the amount of current to be measured,
Caution: amount
current is nown, s art w1 t e
jack, Current will flow through the
meter shunts, but not throu~h the meter
movement, as soon as connec ion throu~h
these ~in jacks is made. Push down t e
~~~y button marked PRESSto read the
meter, This ermits current to flow
t roug e me movemen • e me-
ter indication 1s less than 3 amperest
connect to the 3Apin jack, and if i
is less than 150 milliamperes, connect
to the 150MApin jack,
(F) Resistance Measurements
3.09 When resistance is to be measured, set
the ut*er toggle switch at its DCposi-
tion, ande lower toggle switch at its RES
position, Connect one test cord to the X pin
jack, and the other test cord to either the R,
RxlO, RxlOO, or RxlOOOjack depending on the
value of the resistance to be measured. Short-
circuit the test cords and turn the BATTERY
ADJUSTMENTlmob until a zero reading is obtained
on the ohms scale, This adjustment is necessary
to calibrate the meter circuit to the exact
voltage and condition of the dry-cell battery,
Whena zero adjustment can no longer be obtained
within the range of the BATTERYADJUSTMENT
lmob, the battery of the meter is no l~nger in
suitable condition and should be replaced
(Paragraph 4.03). Connect the test cords to
the circuit to be measured and read the resis-
tance scale of the meter.
3.10 The resistance scale is not uniform, and
the pointer moves farther for a particu-
lar value of resistance change when over the
left side of the scale than when over the right
side of the scale. Therefore, greater accuracy
of reading results when the scale is selected
which as faras possible keeps the pointer near
the middle range of its swing. The following
table suggests the most favorable connections
to the meter for various ranges of resistance
values to be measured.
Resistance - Ohms
0-200
100-2000
1000-20,000
10,000-1.000.000
Heter Jack Connections
X and R
X and RxlO
X and RxlOO
X and RxlOOO
3.11 When making resistance measurements the
drain on the 4-1/2-volt test battery is
dif'f'erent f'or connections to ea.ch pair of' jacks
(i,e,, X and R, X and RxlO, X and RxlOO, or X
and RxlOOO), This may, especially with a used
Page 5

TCI Library https://www.telephonecollectors.info/
SECTION 100-513-101
battery, cause the zero setting to need a dif-
ferent BATTERYADJUSTMENTknob position for
each resistance measuring 8Cale range, There-
fore, when accuracy of the measurement is im-
portant, it is desirable to check the zero set-
ting (by short-circuiting the test leads) each
time the scale connection to ~he meter jacks
is changed, Also, when connected to the X and
R jacks, the current drainis relatively heavy,
and it may be desirable to recheck the zero
setting from time to time while using this
scale range, The meter is accurate for resis-
tance measurements within +2 per cent, at mid-
swing of the pointer, The current drains at
zero reading on the ohms scale, for each test
lead connection, are approximately as follows:
Test Lead Connection Current - MilliamEeres
X and R 129.5
X and Rxl0 12.95
X and Rxl00 1.3
X and Rxl000 0.13
3,12 If a 4,5-volt battery of a suitable size
is not available, any 4,5-volt battery
can be connected externally for making resis-
tance measurements, If this external 4,5-volt
battery differs appreciably as to its internal
resistance, from the types of batteries normal-
ly used in the meter• the accuracy of the lower
resistance scales may be slightly decreased.
3.13 To use an external battery, connect the
negative terminal of the battery to the
-V terminal of the meter, Connect the positive
terminal of the battery to one side of the cir-
cuit whose resistance is to be measured. Con-
nect the other side of the resistance to the
proper pin jack for the scale required (Rxl0,
Rxl00, or Rxl000),
(G) CaEacitance Measurements
3,14 The following Paragraphs (3.15 through
3,21) cover the use of the M9BMeter for
measuring capacitance by the ballistic kick
method of testing. By this method, the meter
may be used to make capacitance measurements
within the limits of approximately 0.1 mf to
200 mf, with a reasonable degree of accuracy.
3,15 General :Method. In measuring capaci-
tance, the resistance measuring portion
of the M9B Meter circuit is used, with the
test leads connected to the X and RxlO00 pin
jacks for the lower capacitance values or to
the X and Rxl00 pin jacks for higher values.
The maximum swing of the pointer at the in-
stant of connection to the capacitor is read
on the 0-150 scale on the upper part of the
meter dial. This scale reading is then con-
verted into capacitance in microfarads by use
0£ the curves in Fig, 6 or 7, SeYeral repeti-
tions of the swing generally are required for
Page 6
2.0
1.9
I.&
1.7
I.&
i.5
I
7
6
5
4
3
.2
.I
c~Wi~"'""'-j
AfTER
~
SHORT
CIRCUIT I
I
l
I
I
' I
I I
I ,'
I i
'/
n·
I /1,;'
~
--
:..-::
)
,,
/
I
J
I
"
/
,/
[/ -i-
!
;
h- CURVE 8 1 I
SWING
USING
REV.
SWITCH j
I
~Y~"" J
AFTER y
SHORT
CIRCUIT
I
I
I
I/ CURVE B\
SWING
USING
/ REV. SWITCH
), ....
_,...,~
·""
-
....
-
2
0
I
9
8
17
16
I
5
I
I
m
4oz
3 <
<
I
2"'
!
II
I
I
0 ..
::E
I
9
8
~
~
7
~
,-- If, <
u
......
5
4
3
2
I
0
0
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
METER DEfLtCTION ON 0-150 SCALE
Fig. 6 - Capacitance Measurement - Smaller
Values - Usin~ X and Rxl000 Jacks
20
19
,e
17
16
15
1D 14
0
~ 13
12
"'
..,
~I
:, I
y IO
..
~ 9
..,
~ II
~
u 7
It
~ 6
5
4
3
CURVE A'""' j
&WING
AFTER \f
SHORT
CIRCUIT I
I
.
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·'
I I
I I
I I
' I
IL'
' /I 1,.-I/
2
J,..- L.,.,-•
I
' CURVE Bl
•
I/ SWING
; USING
REIi
SWITCH
I
j
I
' c~i~t--
AFTER \
j SHORT
CIRCUIT
I I
I
)
I/
J
,v
V
,v
,,...,....... -L,.•
1.-- i--
I
'
I
I
j
I
CURVE 8\
SWING
USING
REV
SWITCH ...
.....
.....
I--
L>"
200
90
80
70
60
50
40 l1l
30 2
I
I
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<
20 <
"'
10 ~
a:
:,
00 u
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90 :I!
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80 tf
z
~
70 V
It
60 ~
50
40
30
20
0
I
~
1:::::
0 0
0 10 20 30 40 50 60 70 &O 90 100 110 120 130 140 150
METER OEFLECTION ON 0-150 SCALE
Fi~, 7 - Capacitance MeaGurement - Larger
Values - Using X and Rxl00 Jacks

TCI Library https://www.telephonecollectors.info/
accurate reading, The test may be made by ei-
ther of two methods; by -short-circuiting the
capacitor to full? discharge it and then making
connection to the meter; or, by reversing the
polarity of the connections from the meter to
the capacitor, without intermediate discharge
of the capacitor, The latter method requires
the use of an auxiliary switch inserted in the
connections between the meter and capacitor
as
shown in Fig. 9. When the short-circuiting
method is followed, no auxiliary switch is re-
quired; however, if desired, a switch may be
used in the test leads to discharge the capac-
itor and then reconnect it to the meter, in
order to simplify the procedure (see Fig. 8),
The reversing switch method, covered in Para-
graph 3.
18,
should not be used for electrolytic
capacitors, since a single polarity should be
used v1hen testing this type of capacitor; that
is, the(+) or X terminal of the meter should
alv1a,rs connect to the (+) terminal of the ce-
pacitor. When using the reversing method, the
magnitude of the pointer swing is approximately
double that obtained after shorting the capac-
itor. The dotted curves Band B• in Figs, 6
and
7
are provided for use when the reversing
switch is employed, and solid curves A and A•
when the short-circuiting switch is used,
3.16
The table below summarizes the connec-
tions which may be used for various
values of capacitance, and the curves which
are appl~cable for the testing procedure used.
The A' and B' curves in both Figs.
6
and
7
correspond to the lower portions of the A
and
B curves respectively, but are plotted on
a
larger scale for easier and more accurate
reading of the smaller values of capacitance,
It is therefore preferable to use curves A• or
B• if the pointer swing is low enough to be
read on them.
3.17
Electrolytic Capacitors. Before measur-
ing the capacitance of electrolytic ca-
pacitors which have not been in service for
e.n
extended period,the film should be restored by
connecting the ce.paci tor to a d-c voltage ap-
proximating the normal working voltage of the
capacitor, in series with a lamp, for about
30
minutes, If a capacitor is tested in the cir-
cuit, and there are any shunting paths around
the capacitor, at lee.st one terminal should be
discom1ected before proceeding.
Capacitance Pin Jack
Range Connectiors
0,1
to
2.0 mf
X
and Rxl000
2.0
to
20 mf
(X
and Rxl000
(
or
(X and RxlO0
20
to
200 mf X
and Rxl00
Fig,
6
6
7
7
155 1, SECTION100-513-101
3.18
Procedure, The following procedure for
measuring capacitance is to be followed
when neither
a
sho~t-circuiting switch nor
a
reversing switch is to be used, r'hen a short-
circuiting switch or a reversing switch is
used, the procedure given below is modified as
covered in Paragraph
3,20
or
3.21.
(1) For higher capacitance measurements,
use the X and Rxl00 pin jacksJ for
lower capacitance measurements, use the X
and Rxl000 pin jacks (see Paragraph
3.16).
(2) Set the meter switches to their DC and
RES positions, connect the test cords
to the meter jacks to be used and adjust
the setting of the BATTERYADJUSTMENTknob
for zero reading on the resistance scale
(as covered in Para~raph
3.09),
(3)
Connect the test lead from the X pin
jack to one terminal of the capacitor
(if the capacitor is electrolytic, connect
this lead to the positive terminal).
(4)
With the other test lead disconnected
from the meter, connect its clip end
to the other capacitor terminal (negative,
if capacitor is electrolytic),
(5)
Then, quickly insertthe other terminal
of this test lead into the Rxl00 or
the Rxl000 pin jack, at the same time
watching the meter needle to determine its
maximwn swin~.
If
this oonneotion is not
made quickly a full swing of the pointer
will not be obtained,
(6)
Read the maximl.Ull swing on the
0-150
(upper) scale and convert the reading
to microfarads by use of the solid curv~s
A or A• in Fig,
6
or
7;
use Fig.
6
for
connections to the X and Rxl000 jacks; use
Fig.
7
for X and Rxl00 connections.
(7) To repeat the test, remove the
lead
from the meter Rxl00 or the Rxl000
jack, touch it to the capacitor to short-
circuit and discharge it, then rel?eat the
~onnection to meter, as in Items
(5)
and
(6) above.
Aoolicable Curve
Short Get, Rev. Sw,
Method- Method-
Solid Curve Dotted Curve
A• B'
A
B
A'
B'
A
B
Page 7

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SECTION 100-513-101
SHORTING
SWITCH
TO
X PIN JACK_+.._ ____ "°
OF METER
TO RXIOOOR _
RxlOOO PIN ----.-o
JACK OF METER
TO POSITIVE
------TERMINAL OF
CAPACITOR
TO NEGATIVE
------TERMINAL OF
CAPACITOR
Fig. 8 - Wiring of Shorting Switch
3.19 Procedure Using Short-circuiting Switch.
For greater convenience in making capac-
itance measurements, a switch may be used to
short-circuit the terminals of the capacitor
before each test. A quick-acting DPDTtoggle
switch may be used for this purpose, wired as
shown in Fig, 8. After the switch is connected
to the meter jacks and to the capacitor as in-
dicated in Fig. 8, operate the switch quickly
from its short-circuit position to charge the
capacitor, the charging current producing the
meter pointer swing; then restore the switch
to its short-circuit position to discharge the
capacitor. If repetition of the swinis is de-
sired, it may be obtained by repeated opera-
tion of the switch. Otherwise, the method de-
scribed in Paragraph 3.18 is followed, using
the solid curves (A or A1) in Fig. 6 or 7.
TO +
X PIN JACK------ ..
OF METER
TO RXIOO OR
RXIOOO PIN------
JACK OF METER
Fig. 9 - Wiring of Reversing Switch
3.20 Procedure Using Reversing Switch~ If
desired, a reversing switch may be used
with the test leads in place of the shorting
switch described in Paragraph 3.19. Fig. 9
shows a snap-action double-pole double-throw
toggle switch wired as a reversing switch and
indicates the connections to the meter and to
the capacitor. After these connections have
been made, operation of the switch to either
position reverses the polarity of the voltage
applied to the capacitor by the meter and pro-
duces a swing of the meter pointer. Repeti-
tions of the swing maybe obtained by operating
the switch back and forth until the maximum
swing is ascertained, The reading obtained by
this method is converted to mi_crofarads by us-
ing the dotted curves (B or B') in Fig. 6 or 7.
Page 8
Since the effective change in voltage across
the capacitor when using a reversing switch is
twice that obtained when using the uni-polarity
short-circuiting switch, the resulting swing
of the pointer is approximately doubled for a
given value of capacity.
3.21 Leaka e Resistance of Electrol ic Ca-
paci ors. n measuring capaci ance as
c6vered in the preceding paragraphs, the meter
needle should return to O after the initial
swing. In checking electrolytic capacitors,
the needle, after its swing, will not return
entirely to zero but generallywill stabilize
at some value above zero, depending upon how
completely the film of the capacitor is formed
and on its leakage resistance. The amount.of
leakage resistance in ohms can be read on the
ohms scale in the usual manner, i.e., as 100
or 1000 times the actual reading on the meter,
depending upon the meter scale used. In using
the M9BMeter to measure the leakage of capac-
itors, a lov1 voltage (4.5 volts) is applied,
as compared to the usual operating voltages,
Therefore, this test, in general, imposes a
less severe condition than the service voltages
to which the capacitor is normally connected.
Leakage resistance at the low voltage at which
the test is made should generally be 100,000
ohms or greater, for capacitors in good condi-
tion. The amount of leakage which can be tol-
erated depends upon the circuit usage of the
capacitor, Leakal!,e current, of course, is con-
verted into heat loss in the capacitor, and
when appreciable, may hasten the deterioration
and failure of the capacitor.
4. MAINTENANCE
(A) Voltage Accuracy
4,01 No regular routine accuracy tests are
required but it is recomi~ended that the
d-c voltmeter be occasionally checked against
a voltmeter of known accuracy. The permissible
error is 2 per cent. of full scale, at any
point on a scale.
4.02 The a-c
checked
curacy. The
of full scale
voltmeter may be occasionally
against a voltmeter of known ac-
permissible error is 5 per cent.
at any point on the scale.
(B) Battery Replacement
4.03 The battery should be replaced when it
is impossible to adjust the meter pointer
to the zero ohms mark when the test leads con-
nected to the X and RxlOO jacks are short-cir-
cuited (Paragraph 3.09), or when frequent ad-
justment of the BATTERYADJUSTMENTknob is re-
quired when measuring resistance. If desired,
the voltage of the battery may be measured
without removing it from the meter as follows:
(1) Arrange the meter for d-c voltage meas-
urement.

TCI Library https://www.telephonecollectors.info/
(2) Connect one
jack and the
15V pin jack.
test lead to the X pin
other test lead to the
(3) Short-circuit the test leads and read
the battery voltage on the 0-15 volt
scale.
4.04 When replacement of the battery i s re-
quired, use one of the followin g 4-1 / 2
volt batteries which have suitable chara cte r-
istics and the proper type terminals for use
in the meter.
Bright Star 03-17s
Eveready -781
Burgess 536o
Ray-0-Vac 531R
Bond 317
4.05 The lo\•1er portion of the meter casing is
removable from the meter top panel by
loosening the four scre ws which are located on
the face of the panel near the edges, The bat-
tery slides into a bracket formed to fit the
battery and mounted on the rear of the meter
housing. The leads to the battery are equi pped
with spade terminals to fit under the screw
terminals of the battery. The REDlead connects
to the positive(+) terminal oTThe battery,
4.06 A coating of nonfluid oil (New York and
New Jersey Lubricant Co, No. K-000) is
applied to the edges of the casing and panel
which fit together, in orde~ to pr~vide a mois-
ture seal, Care should be taken not to wipe
off this oil v:hen the case is opened, so that
the seal can be maintained when the casing is
put back together. A rubber gasket may be pro-
vided on some meters in place of the oil or may
be obtained if preferred. (Part 6.)
ISS 1, SECTION 100-513-101
4,07 The screws holding the casing and pane
together are 6-32 (,138-32), 5/8
11
long,
oval-head machine screws,
5. REPAIR
(A) General
5,01 The re placement of parts in the field,
ot her t han replacement of the battery,
is not recommended, since the calibration of
the meter may be affected by variations in
re-
placement parts. If, however, parts are re-
moved or replaced for any reason, the follow-
in g instructions should be carefully followed,
5.02 All apparatus parts are attached to the
underside of the top panel of the meter
(Fie. 10), This panel maybe removed by taking
out the four screws which attach it to the me-
ter case, The edges of the panel and case may
be coated with oil, or a rubber gasket may be
provided in order to moisture-seal the meter.
If a coating of oil is used, take
care
not
to
wipe it off when removing the top panel or
mak-
ing repairs, The oil used for this purpose and
the rub ber gasket are listed in Part 6.
5.03 Identification of Leads.
If
it is neces-
sary to re move parts from the meter for
replacement or to remove leads or parts in or-
der to gain acces11 to a defective part, make
a record of the connections removed and of the
location of any part removed, in ord ·er that the
connections and parts can be correctly replaced.
5,04 Electrical Connections. When replacing
internal wiring, clip the leads as close
as possible for satisfactory connection. Take
care to use only enough solder to make a secure
BATTERY
8 1 RESISTOR
P l
RESISTORS R 7
THROUGH Rl6
ANO R2.0 -- --..--
PIN JACK
CONNECTORS
SWITCH
01 SWITCH
03
Fig, 10 - Location of Parts of M9BMeter
ESISTOR
BRACKET
Page
9

TCI Library https://www.telephonecollectors.info/
SECTION 100-513-101
connection. Do not heat the tenninal or con-
nection more than necessary to avoid possible
damage to resistors, rectifier, etc.
Caution: Never change the location of
parts or wiring leads. Such a change
may necessitate complete recalibration
of the meter, Never chan e the len th
o wiring eads. Use o. gauge wire.
Moisture-resistant wire,Western Elec-
tric Company D-142203, No, 22 gauge,
solid or stranded, or KS-9819 wire
is used in wiring the meter; this or
its equivalent should be used for re-
pairs,
CLAMPING
RING
' "7 r
~~
cf BATTERY
V HOLDER
Fig, 11 - Location of Parts of M9BMeter -
Battery Holder and Meter Unit Re-
moved
5.05 Replacement of Parts, In replacing parts,
take care to replace all parts in the
same manner as originally installed. Be par-
ticularly careful to replace the phenol-fibre
insulating washers and bushings correctly.
(B) Meter Unit
5,06 The meter unit is housed within a cylin-
drical phenol-plastic wall which is.part
of the top panel (Fig. 11). If it is necessary
to remove the meter unit, it must be handled
with care, and particular care must be taken
when replacini;; the unit in its housing as cov-
ered by Item ~6) below. Instructions for re-
moving and replacing the meter unit follow:
(1) Disconnect the leads from the battery
and slide the battery from its holder.
Page 10
(2) Remove the battery holder by removing
the screws which attach it to the meter
unit housing,
(3) Loosen the two screws which fasten the
spring clips and turn the clips clear
of the meter unit.
(4) Note t~e color of the lead attached to
each of the meter tenninals on the rear
of the meter unit, Disconnect these leads
by removing the tenninal screws.
(5) Place the palmof the hand over the me-
ter unit and turn the panel face upward
so that the meter unit slides out into the
hand.
(6) Before replacing the meter unit in the
housing, carefully note the position
of the turned-up brass tab close to the
center of the meter assembly which deter-
mines the zero setting of the pointer (Fig,
11). This brass tab must be engaged by one
of the small slots in the zero corrector
which is 'mounted in the center of the glass
meter window. Holding the meter unit face
upward in the palm of the hand, carefully
slide the meter panel housing down over it
in such a way that the relative position
of the brass tab and the engaging slot of
the zero corrector will be approximately
right; then v•:hen almost fully in place,
carefully turn the meter unit in the housing
until the pointer adjusting tab slides in-
to the slot in the zero corrector. If the
meter unit face is not lined up straight
in the shell, carefully rotate the meter
unit in order to position the dial properly•
keeping the brass tab and zero corrector
engaged. Use care in perfonning this oper-
ation since serious damage may be done to
the meter unit by careless or rough han-
dling,
(7) Holding the meter unit in place, turn
the panel fa_ce down; reposition the
spring clips; replace the meter unit ter-
minal leads, the battery holder, and the
battery.
(8) Replace the panel on the casing, place
on a level surface, and adjust the zero
reading of the pointers by turning the zero
corrector with a screwdriver or small coin.
(C) Meter Glass and Zero Corrector
5,07 The meter glass is moisture-sealed to
the meter case by caulking between the
outer rim of the glass and the case. A light-
colored plexiglass ring, within the cylindrical
meter unit housing, is held against the window

TCI Library https://www.telephonecollectors.info/
by a forced-in brass clamping ring. If it is
necessary to replace the glass window and zero
corrector assembly, proceed as follows:
(1) Remove the meter unit as covered by
Paragraph 5.o6 above.
(2) Using a thin-bladed screwdriver, pry
the brass clamping ring away from the
inside of the meter unit housing at one
point, bending the brass away sufficiently
so that long-nose pliers can be inserted
to grip it.
(3) Grasp the bent part of the brass ring
with the pliers and remove the ring,
(4) Turn panel face upward so that the
plexiglass ring will slide out.
(5) From the top of the panel, pry the
glass away from the case by inserting
a small screwdriver blade or knife blade.
Carefully scrape the old caulk from the
case.
(6) Reassembling, seal the glass to the
meter case with Hallemi te No. 770 caulk
mixed with 3 per cent, litharge. If Halle-
mite caulk is not available, use G,E.Co,
Glyptal mixed with enough talc to give it
body, Wipe off any excess before it sets.
155 1, SECTION100-513-101
(7) The clamping ring may sometimes be used
again if carefully reshaped with pliers,
or a new ring maybe used. Push the clamp-
ing ring down evenly until it rests firmly
against the plexiglass ring, A wooden
block, if available• may be used to force
the clamping ring in.
(8) Replace the meter unit and adjust the
zero reading as covered in Paragraph
5.o6, Item (5) through (7) above.
(D) Pin Jacks
5.08 The pin jack assemblies are screwed into
drillings in the underside of the top
panel, Each pin jack (Fig, 12) consists prin-
cipally of the outer shell which screws into
the panel, the pin jack body, a lock nut, and
lock washer. Two lengths of pin jacks are used.
Additional washers and nuts are added to the
stem of the longer jacks for connecting wires,
lugs, etc., as required. A pin jack, if taken
•
ASSEMBLED
PIN JACK ..
OUTER
SHELL
Fig. 12 - Pin Jack Assembly and Parts
Notes,
l, Wires designated "A" shall be per Spec, KS-9819 ,{/e2AWGSolid Conductor,
2, Wires designated "B" shall be per Spoo, KS-9819 ,(/e.2AWGStranded Conductor,
:,. Wires designated "c" shall be furnished with appara.tua,
4, Wires designated "T" shall be ,(/1.22AWGBare Tinned Copper,
5. Wires designated "S" shall be covered with No, 17 Varnish Tubing per LRM186.
6, All soldering shall be in accordance with Spec. KS-512 Method E, using Solder fl}, Flux No. 2,
7. All connections to be mechanically secure before soldering.
8. Battery leads shall be arranged so that cord tips do not Come into contact with any electrical
connections.
9. No. 11 Varnished Tubing per LRl1186. approx. 1/2 in. long shall be assembled over the ends of
these leads and soldered connections,
Fig. 13 - M9BMeter - Wiring Diagram Page 11

TCI Library https://www.telephonecollectors.info/
SECTION 100-513-101
apart for repair or inspection, must be care-
fully reassembled as follows~
(1) Screw the pin jack into the shell as
far as it. will 1,0; then back it off a
little (not over 1/4 turn).
(2) Place the lock washer and lock nut on
the protruding end of the pin jack and
screw the lock nut down to hold the pin
jack in place, Use care that the inner
part is not turned from the position de-
scribed in Item (1) above whenthelock nut
is tightened. If the tips of the inner
jack "bottom," they will not grip properly
when the pin terminal of the test load is
inserted,
(3) If pin jacks do not grip tightly, the
slotted ends of the tips of the pin
.jack body may be adjusted using pliers at
the time that the pin jack is disassembled.
(4) It is unnecessary to remove the outer
shell from the panel in order to in-
spect the body of the jack, Do not remove
the jacks from the panel unnecessarily, as
the bushing threads may be da.r.1agedby doing
this repeatedly or carelessly.
6. REPLACEMENTPARTS
6.01 The following is a list of the more readi-
ly replaceable parts of the M9BMeter:
Part
Battery, 4-1/2 volts.
Page 12
12 Pages
nanufacturer and No.
Bright Star 03-17S,
Eveready 781,
Burgess 5360,
Bond 317 or
Ray-0-Vac 531R
Part
Gasket, rubber;
for use between
top panel and case.
Meter Unit Assembly
(meter movement,
scale plates and
pointers),
Oil, nonfluid; for
moisture-sealing
top panel to case.
Pin Jack (longer size)
Potentiometer
(battery adjustment)
Resistor; for replacing
R-4; may require sli ght
modification of resis-
tance of secondary wind-
ing to obtain accurate
readin gs on 0-1000-ohm
scale.
Zero Corrector
Assembly (zero cor-
rector moimted in
hardened glass me-
• ter window)
Manufacturer and No.
W. E. Co. BA-109230
H. E, Co, P-480532
N, Y. and N. J,
Lubricant Co. :/IK-000
\;. E, Co, P-480657
Allen-Bradley
J-Ul032-P4048-4
W, E, Co, D-166804,
with secondary wind-
ing of 33.5 ohms
W, E. Co. P-285979