Keithley 149 User manual

INSTRUCTION MANUAL
MODEL 149
MILLI-MICROVOLTMETER

WARRANTY
We warrant each of our products to be free
from defects in material and workmanship. Our
obligation under this warranty is to repair or
replace any instrument or part thereof which,
within a year after shipment, proves defective
upon examination. We will pay domestic
surface freight costs.
To exercise this warranty, call your local
field representative or the Cleveland factory,
DDD 216-248-0400. You will be given assist-
ance and shipping instructions.
REPAIRS AND RECALIBRATION
Keithley Instruments maintains a complete re-
pair service and standards laboratory in Cleve-
land, and has an authorized field repair facility
in Los Angeles and in all countries outside the
United States having Keithley field repre-
sentatives.
To insure prompt repair or recalibration serv-
ice, please contact your local field representa-
tive or the plant directly before returning the
instrument.
Estimates for repairs, normal recalibrations,
and calibrations traceable to the National Bu-
reau of Standards are available upon request.

MODEL 149 MILLI-MICROVOLTMETER CONTENTS
TABLE OF CONTENTS
Section Page
1. INTRODUCTION . l-1
Specifications . 1-2
2. OPERATION. . 2-1
Operating Controls . . . 2-l
Preliminary Set-Up . 2-l
General Precautions. . . 2-2
Measuring Voltage. . 2-3
Other Applications 2-4
3. CIRCUIT DESCRIPTION. 3-1
Input Circuit.
. 3-l
AC Amplifier . . 3-l
DC Amplifier . . . . . . 3-l
Zero Suppression . . . . 3-2
Other Controls .
. . . . 3-2
Power Supply . . . . . . 3-2
Section Page
4. MAINTENANCE. . . . . . . . . 4- 1
Trouble-Shooting . . . . .
Excessive Output Noise . . . .
Output not Zero with Input
Terminals Shorted . . .
220-Volt Operation . . . . . . .
4-l
4- 1
4-2
4-3
5. REPLACEABLE PARTS. . . . 5-l
Replaceable Parts List . .
How to Order Parts . . .
Model 149 Replaceable Parts List
Models 1483, 1484 Replaceable
5-1
5-l
5-2
Parts List. . . . . . . . 5-6
Model 1491 Replaceable Parts List 5-7
Model 1501 Replaceable Parts List 5-7
Model 1502 Replaceable Parts List 5-7
Voltage and Resistance Chart . 5-9
Schematic Diagram. . . . . . 5-11
Green Repair and Calibration Form 5-13
* Change Notice . . . . . Last
Page
K
Yellow Change Notice sheet is included only for instrument modifications
affecting the Instruction Manual.
1068R

MODEL 149 MILLI-MICROVOLTMETER
SECTION 1. INTRODUCTION
INTRODUCTION
l-l. GENERAL.
a. The Model 149 Milli-Microvoltmeter is a stable, versatile instrument for measuring
low-level dc signals. It functions as a voltmeter from 100 nanovol s full scale to 100
millivolts. It also operates as a dc amplifier with gains up to 10' for driving recor-
ders.
b. The low noise level of the Model 149, together with its long-term stability, makes
it ideal for many measurements requiring extreme power sensitivity.
C. Typical applications include measuring the output from strain gages, thermopilcs,
thermocouples, bolometers, phototubes, ionization chambers, scintillation counters, and
barrier layer cells. Other applications are found in cell studies, measurement of elec-
trochemical potentials, electrolytic corrosion studies, molecular weight analysis and
Hall effect studies.
d. In addition to its use as a direct indicator of minute potentials and currents, the
Model 149 may also be used as a null detector in Wheatstone or Mueller bridges.
e. An important feature of the instrument is zero suppression up to 100 times full
scale in place of the usual more limited meter zero. This permits measurements of small
signals in the presence of large thermal emf's or other masking dc signals.
FIGURE 1. Keithley Instruments Model 149 Milli-Microvoltmeter.
l-l

INTRODUCTION MODEL 149 MILLI-MICROVOLTMETER
l-2. SPECIFICATIONS.
RANGE: 0.1 micro"olt (10 x 10-8 volt) full scale to 100 millivolts on zero-center meter.
13 overlapping ranges in lx and 3x steps.
ACCURACY: *2% of full scale on all ranges exclusive of noise and drift.
ZERO DRIFT: Less than 10 nanovolts per hour or less than 30 nanovolts in any *-hour per-
iod after approximately Z-hour warm-up with reasonably constant ambient temperature.
Long-term drift is non-cumulative.
INPUT NOISE (with input shorted): Less than 0.6 nanovolt rms (3 nanovolts peak-to-peak)
on most sensitive range.
INPDT CHARACTERISTICS:
m
0.1 P"
0.3 ,I"
1.0 &I"
3.0 ,1"
10.0 1"
30.0 )A"
100 pv and above
Input Resistance
Greater than,
ohms
10 k
30 k
100 k
300 k
1M
3M
10 M
Maximum Source1
Resistance,
ohms
100
300
lk
3k
10 k
30 k
30 k
Note:l Source resistances higher than the recommended maximum will increase noise
and rise time.
LINE FREQUENCYREJECTION: Greater than 5O:l on the most sensitive r~ange. (Ratio of im-
pressed peak-to-peak line frequency voltage at input to indicated dc voltage.)
ISOLATION: Circuit ground to chassis ground: Approximately 10' ohms shunted by 0.05 mi-
crofarad. Circuit ground may be floated up to *400 volts with respect to chassis ground.
RISE TIME (10% to 90%): -
O.l-microvolt Range: mess than 2 seconds when source resistance is less than 10% of
maximum; 4 seconds using maximum source resistance.
0.3-microvolt to lOO-millivolt Ranges: Less than 1 second when source resistance is
less than 10% of maximum; 2 seconds using maximum source resistance.
ZERO SUPPRESSION: Up to at least 1 millivolt on the microvolt ranges and up to at least
10 millivolts on the millivolt ranges. Stability is such that 100 times full scale may
be suppressed.
RECORDEROUTPUT:
output: *lO volts dc at up to 5 milliamperes for full-scale meter deflection.
Resistance: Less than 10 ohms within the amplifier pass band,
Gain: 10 volts
Range setting in volts
1-2 1167R

MODEL 149 MILLI-MICROVOLTMETER INTRODUCTION
Noise: Input noise times gain plus modulation products.
Modulation Products: Less than 2% peak-to-peak of full scale with input shorted.
CONNECTORS: Input: Special connector. Front Output: Binding posts. Rear Output:
Amphenol 80-PC2F.
POWER: 105-125 or 210-250 volts, 60 cps, 50 watts. SO-cps models available.
DIMENSIONS, WEIGHT: 7 inches high x 19 inches wide x 13 inches deep; net weight, 24 pounds.
ACCESSORIES SUPPLIED: Model 1501 Low Thermal Input Cable with alligator clips; mating
output connector; length of low-thermal solder.*
-'t The solder is screwed to the right side of the copper input chassis, located inside the
Model 149. Remove the top cover to reach the solder.
1-3

MDDEL149 KLLI-MICROVOLB OPERATION
SECTION 2 - OPERATION
A.
OPERATINGCONTROLS
The controls of the Model 149 are simple and conveniently
placed. Their functions are as follows:
ON-OFF switch is located to the right of the panel
meter.
FUNCTION switch selects the function which Is to be
used: MilliVOltS, Or
!dCrOVOltB.
2AN'm switch selects the full scale multiplier of
the function selected by the FUNCTION switch.
ZERC SUPPiWSScontrols consists of the ZERORANGE
switch which selects the coa.188 range of sup-
pressing voltage in discreet steps and the ZERO
SET potentiometer which gives continuously
variable fine control Including settings through
TieI-0.
B. PRELIMINARY SET-UP
Connect the instrument to the power line. Unless otherwise
marked the unit may be used on 117 volt, 60 cps line. To con-
vert to 220-volt operation, refer to the
MAIN'lXK4NC!E section.
A three-wire line cord is furnished, which grounds the cabinet.
If a three-wire receptable is not available, use the two-pin
adapter furnished, and ground the third lead to an external
ground.
Set controls *a followa:
Function: Millivolts
Range: 100
zero suppress: OFF
Input: Short the input leads together.
2-1

OPE3ATION KNEL
149 MILLI-MICROVOL-R
C. GENERALPRECAUTIONS
1. Source Resistance - 1n
Section luncler the Input Re-
sistance SpeCifiCatYiOg the maximum source resistance for use with
each voltage range is specified. Reasonable operation is possible
with source resistance up to ten times greater than those specified,
however, the measurement will suffer from a considerable decrease in
speed of response, and measuring accuracy. If the instrument is
left completely open-circuited, the meter will generally drift off
scale on any range.
2. Shielding - Since the instrument operates with a modulator
frequency of 120 cps, it is not generally sensitive to 60 cps pick-
up unless it is large enough to overload the amplifier. The pickup
may be a source of difficulty when using the amplifier with high
impedances on ~the more sensitive voltage ranges. In these cases it
is desirable to shield the leads and the sources as completely as
possible. In some cases a simple low-pass filter at the input to
eliminate frequencies of about 1 cps and above will be helpful.
No use is made of an input filter in this instrument since any input
series impedance due to the filter will increase the input noise and
the thermal drift. When operating above ground, the case of the in-
strument must be grounded.
3. Determination of Excessive AC Pickup - A terminal attached to
the output of the AC amplifier at the point of the demodulator is
provided at the rear of the instrument. It is labeled DEMOD. OUTPUT.
If an inability to make consistent readings persists, it is possible
to check for the presence of excessive pick-up by observing the
wave-form at this point. With the input shorted the picture should
be approximately as shown in figure 2. If excessive pickup is ob-
served it will look as shown in figure 3.
The circuit will operate
reasonably well as long as the wave-form does not clip as shown
in figure 4. At this point the operation will be erratic.
FIOUIlE2
--I.-
lo v P-P
t
c
40 v P-P
t

MODEL 149 MILLI-MICROVOLl'METI OPERATION
FIGURE 4
4. Thermal EMF - Extreme precautions have been taken in the input
circuit to minimize thermal EMF's so the residual RMF is usually less
than 0.5 uv. The material used in the input circuit is pure copper.
Any other metal will generate a thermocouple potential. Lead solder is
particularly troublesome. Where thermal W's are a problem, soldering
should be done with the cadmium-tin solder supplied with the instrument.
5. Input Noise - The noise at the input is a function of input
resistance and is approximately given by
E = 1.29 x 10-loum
where E is the RMS noise, and R is the source resistaixe. It is assumed
that the bandwidth of the instrument is about 1 cps and the temperature
is 80° F. If noise is observed, calculate the theoretical noise and
compare results. Also bear in mind that only wire-wound resistors
approach the ideal resistor. However, if Evanohm or Manganin resistors
are used, a considerable thermal EMF of the resistor material against
copper will be observed.
6. Checking the Zero Point - At low levels, spurious W's may be
generated simply by contact between the input leads and the terminals
under test. If possible, always leave the instrument connected and
adjust the zero after establishing a zero reference in the apparatus
under test. For example, in bridge measurements, disconnect the bridge
exciting voltage; or with a phototube, shield the tube from light.
7. Overloads - The current applied to the input circuit should be less
than one milliampere dc steady state, 10 milliamperes dc short-term.
When the FUNCTION switch is on the MILLIVOLTS position, the off-scale
impedance can be as low as 1000 ohms. On the MICROVOLTS position, it may
approach one ohm.
D. MEASURINGVOLTAGE
1. Direct Voltage Measurements - Place the FUNCTION switch at MILLIVOLTS
or MICROVOLTS as necessary for the measurement to be taken. Then turn
the RANGEswitch to more sensitive ranges until the meter gives a usable
deflection,
2. Measuring Voltage Variations - To observe small variations in a large
steady signal, first set the FUNCTION and RANGE switches as described in
D 1. Then operate the ZERO SUPPRESSswitch and potentiometer to reduce
the meter deflection to zero. Increase the meter sensitivity with the range
0667R 2-3

OPERATION MODEL 149 MILLI-MICROVOLTMETER
switch. The stability of the suppression voltage is adequate for 100 x full scale
suppression. Thus, if a thermocouple is suppling a signal of 10 millivolts to the
Model 149 after suppressing the meter deflection to zero, the RANGEmay set at 100
microvolts. If the 10 millivolt signal corresponds to a temperature of 250°C then
after suppression variations of 2.5OC are seen full-scale.
3. Measuring Differential Voltages - When measurements are to be made in a circuit
where the LOWconnection is above ground potential, slide OUTPUT LINK from one of its
posts. This disconnects the instrument circuit ground from chassis ground. NOTDO
attempt to make such measurements where the side of the circuit being measured is
more than 400 volts above external ground potential.
If a recorder is being used with the instrument in this arrangement, the recorder must
not be grounded since the low side of the output is no longer being grounded.
The Keithley Model 370 Recorder is ideal for use with the Model 149 in recording
operations. The Model 370 maximizes the performance of the Mo$el 149 over the
Milli-Microvoltmeter's entire range. The Model 370 can float -500 off ground.
E. QTJEJ APPLICATIONS
1. Null Indicator - The Model 149 makes an extremely sensitive null indicator which
may be used in a wheatstone or Mueller Bridge.
If the bridge is arranged so than one terminal of the detector is grounded, the Model
149 may be used as described in D 1. If the aet~ector must be used floating, remove
the DISCONNECT LINK at the rear and observe the same precautions as in D 3.
7-4 0667R

MDEL149MILIJ-IWROVOLI~ CIRCUITDESCFUFTION
SECTION 3 - CIRCUIT DESCRIPTlON
The Model 149 is basically a narrow-band chopper amplifier employing
negative feedback to stabilize the gain and increase the input impedance.
A.
Input Circuit
Zero Stability: The effect of thermal EMF's generated in the input
circuitry is reduced to nearly the vanishing point by the we of only
copper in the input circuit. All aoldar points are made with a low
thermal cadmium-tin solder. The chopper and chopper transformer
employ copper leads. All switching in the input circuit is accomplished
with copper switch. Critical resistors in the input circuit are
wound of copper wire. The input connector has solid copper,apring-
loaded contacts.
The input voltage is applied to the moving arm of a 120 cpa mechan-
ical chopper. The feedback voltage is connected to the primary
center tap of the input transformer. Thus, the difference voltage
is applied first acro88 one half of the primary and then, with phase
reversal, to the other half. This full wave error signal is stepped
up 90 to 1 by the inputtransformer and applied to the grid of
VI, 'a 6084 low-noise pentode.
B. AC Amplifier
In parallel with the plate load resistor of Vl is a relatively high
Q, 120 cps resonant circuit which narrow the bandwidth and reduce8
spurious signals.
V2 and V3, EF86 pentodes, further amplify the chopper error signal
which is then demodulated synchronously by silicon diodes Dl through
m.
To obtain the 120 cps demodulator driving signal, use is made of the
ripple frequency from a bridge rectifier circuit operating from the
line voltage. The ripple is used in the primary of the demodulator
driver transformer.
C.
lx2 Amplifier
The demodulated signal is applied to the grid of V4. V4, V5, and
V6 form the dc amplifier and.output cathode follower which add
further forward gain to the system and supply output power. Feed-
back around V4, V5 and V6 multiplies the effective capacitance of
demodulator filter capacitor Cl13 by about 1000. This yields the
large equivalent capacitance necessary to smooth the demodulated
error signal. Because of the feedback, spurious noise in the dc
stages outside the pass band of the whole amplifier are effeCtiVely
degenerated.

CIRCUIT DESCRIF'l'ION
D. Zero Suppression
A low-current +10 volt supply is derived from the main dc supplies
using lo-volt zener diodes. Potentiometer Rl54,may be set at any
voltage from -10 to +lO volts, this voltage is applied through ap-
propriate dropping resistors to the feedback point to achieve zero
suppression. The potentiometer is the front panel control marked
ZERO STJF'F'FESS,while switch 53, which determines the portion feed-
aback, is labeled 7LEROSUPPRESS,OFF-INCREASE.
E. Other Controls
Two controls are set at the factory and should require only infre-
quent attention by the user.
R118 is an internal control marked DC AMP BAL. It is used to zero
the DC amplifier, i.e., to set the output voltage to zero when the
demodulator output is zero. This is not very critical since an "n-
balance will simply be fed back to the input to produce a small er-
ror signal to correct itself. R127 is marked CAL. This is the var-
iable portion of the meter multiplier resistance to allow for meter-
to-meter sensitivity differences.
F. power Supply
A standard half-wave rectifier followed by an R-C filter is used to
supply unregulated B l and B- to the output cathode follower.
The unregulated B- is regulated to -150 volts in V7, OA2, and is
used for the negative returns for the dc amplifier.
Unregulated B+ is fed to the plate of V6, 12B4A, the series tube in
a 225-volt electronic regulator. The output voltage from this reg-
"later is divided by R510 and R511 and compared to reference tube
V9, a 5651. The difference signal is amplified by cascade amplifier
VIO, a 12AX7, and applied to the grid-cathode circuit of the series
tube. This regulated 225 volts supplies B+ directly to the dc amp-
lifier, through a decoupling filter (R176, Cl101 to the second end
third ac amplifier stages, and through another decoupling filter
(R103, C104) to the first ac amplifier stage.
Regulated B+ and B- also supply currents to the 10 volt zoner diodes
which are used for zero suppression. This gives two-stage regulation
for these very critical voltages.
Zoner DiodeDllZ regulates the filament voltage of Vl to reduce line
transient effects.

MODEL149 KILLI-KKROVOL'lXl!TER
SECTION 4
- MAINTENANCE
Except for occasional tube or chopper replacement, very little rcalntenance is
required by the Modell@. Components are operated well below rating and solid
state devices are employed where possible to achieve long, trouble-free service.
Certain portions of the input circuit are wired using chopper wire and special
cadmium-tin solder. These special joints are painted red. If, for sny reason,
these joints must be unsoldered or re-soldered, USEONLYCADMIUM-TINSOLDER
ANDACO~-~PPEDSOLDERINCIRONWMCBIIA9NEVERBWUSEDWITHaaDINARYLEAD
TIN SOLDER. A mall spool of cadmium-tin solder is supplied with each instrument.
What may seemto be circuit failure in the milJ.imicrovoltmeter is quite often
found to be an unusuel condition in the entire test set-up. !l!herefore, before
trouble-shooting the instrumeut, check to see whether it operates correctly with:
1. All other circuitry disconnected.
2. Input shorted (with copper leads).
3.
POwerLine voltage and frequency correct.
If the difficulty persists, the following systematic procedure may be employed
to determine the fault.
Reference is madeto the Schematic Magrsm 13621~, and the Voltage-Resistance
Diagram enclosed at the rear of the manuel.
To begin trouble-shooting, short the input terminals, StrapGto I1) with the
link provided. end switch ZEROsuppREsS, OFF-INCREASEto OFF. A Zero offset
of v.1 to 0.4 mlcromlt is normal.
E2ZESSIVEOUTFUTNOISE(INiTlTTpIMINAIs SHORTED)
Because of the vary low signal levels involved, noise in the ac amplifier Is
difficult to trace except by the substitution method. Most likely noise sources
are Vlendthe chopper. If noise persists after replacing the chopper, it is
being generated in the dc amplifier or power supply. A stage-by-stage search
~shouldrevealthe source. Very often the noise is generated by RlG2, low noise
~mtetalfilm resistor. Replace onlywlththe equivalentreeistor. Win-wound
resistors tend to introduce inductive pickup.
To replace the chopper, unplug the cap atthetop. Frcmtha bottom of the&o&l
14.9, removetheplate covering the areaaroundthe chopper base. Unsolder the
chopper leads. Claen out the lead at the input connector; teg the telminsl for
a correct connection later.
Unscrewthe choppermunting screws endlift out
the chopper frca the top.

MUNTEWNCE M2DEL149 MIUI-MICRCVOL
Insert the new chopper from the
top, putting the wire leads through
the holes. For convenience, place
the No. 2 lead nearest the Model
149 side as shown in Figure 5. From
the bottom, secure the chopper with
four No. 4-40 NC-2 screws. Put ap-
proxim&ely 34 In. of teflon tubing
over lead No. 2 and 2+ in. over the
other two Gads.
Solder lead No. 2 to the input con-
nector. Insert a shorting bar into
the input connector to push out the
leads enough to facilitate working
on the connection.
NOTEZ Use soldering iron with a
new solid copper tip end low-ther-
mal cadmium solder for all sol&r
connections painted red. This
solder is supplied tith the Model
149.
Uake sure of goodelectrical
and mecheacal connections.
Conned lead No. 1 to the red lead
Of trensformer-TR37; connect lead
No. 3 to the blue lead of transformer
m37.
l&k8 loops at the leadends,
interlock the loops, and solder Do
not cross ortwistthe leads. SliXe
the tubing over the connections.
FIGURR 5.
Chopper Replacemnt. View is
from the bottom of &Mel 149.
Twlstshie.l.dleadVaroundchopperleadNo.2asshowninFigure5. Makesure
the end of the shield leed Is free of all-contact. Replacetheplate over the
chopper base. Plug in the cap at the top of the chopper.
ouTmTNoT2ERo (~0.5mcRo~m)wITRINFuTTwMINnrssRo~
Besurethe?mosuPPmss is set to OFF.
7 of v4, to glxmld.
Short the dc amplifier input grid, pin
Use the DCAMPRAL control to set the output to Zero. The
control will becomevery "scratch' but the ad.justment is possible. If this can-
not be done, the dc sqplifler or power supply are at fault. If it ten be set to
zero, the trouble n&be in the ec emplifier or demodulator circuit.
Power suppq - B+ should be about +225011pin 10f va, and B- should
ti -150 on pins 2, 4 or 7 of W. If
V7 is not firing, correct the fault in
the unregulatedB-. If +225 is not present,
940volta) a;t the plate pin g of va.
check for unregulated Dt (about
If the unregulatedB+is all right,
check the tube pin voltages of VS, Vg, and Vu) to locate the faulty tube or
part.
b. ACAmplifier - Removethe output tube (~6) and clip pin 1 of the output
connectortoground. Place the NNCTION switch onMII&IVOLIs, andturnthe
ZEIKISlITandZRRORANUR controls full clockwlse. This puts a large dc error

ImDEL 149 PlILLI-MICROVOLI~2XZR MAINTENANCE
signal across the chopper and input transformer. Use an oscilloscope to check
for the presence of I20 cps at the primacy of the input trsnsfomers (the
two outside temiuals on the chopper terminal block). Absence of signal
means chopper failure (or much less likely, a shorted or open input trans-
former). Listen for audible chopper action and check chopper drive, if
necessary.
If the I20 cps signal is present, check stage-by-stage throughout the ac
emp.l.ifier, reducing the input signal as desired by backing off the ZERO
FiANGEand/or 2220 SET controls, until the failure is discovered.
d. Demodulator Circuit - Check for presence of about 80 volts 2W at the
secondary of the demodulator transformer (at the ends of FLU3 end FtlJ.4).
The tests outlined above will not suffice to pin-point every fault which
may exist. They should, however, lead to the correction of comon failures.
In the event that troubles cannot be corrected by these means, or the user
finds it more expedient, the unit may be returned to the factory for repair
and recalibration at a nominal cost.
220-VOLTOPF&lTION
For 220-volt operation the power tramformer primary connections must be changed.
The juktpers connecting black and black-white together and blue and blue-white
should be removed. The blue and black-white leads should be tied together.
Replace the 1.5~ampere fuse (Keithley Part No. W-8) with a 0.75-ampere fuse
(Keithley Part No. m-14).
4-1

MODEL 149 MILLI-MICROVOLTMETER REPLACEABLEPARTS
SECTION 5. REPLACEABLE PARTS
5-1. REPLACEABLEPARTS LIST. The Replaceable Parts List describes the components of the
Model 149 and its accessories. The List gives the circuit designation, the part descrip-
tion, a suggested manufacturer, the manufacturer’s part number and the Keithley Part
Number. The name and address of the manufacturers listed in the “Mfg. Code” column are
contained in Table 3.
5-2. HOWTO ORDERPARTS.
a. For parts orders, include the instrument’s model and serial number, the Keithlcy
Part Number, the circuit designation and a description of the part. All structural parts
and those parts coded for Keithley manufacture (80164) must be ordered from Keithley
Instruments, Inc. In ordering a part not listed in the Replaceable Parts List, completely
describe the part, its function and its location.
b. Order parts through your nearest Keithley distributor or the Sales Service Depart-
ment, Keithley Instruments, Inc.
I
amp ZXllpere
Mfg. Manufacturer
MtF Metal Film
CbVar Carbon Variable MY Mylar
CerD Ceramic, Disc
:0lU1 Commercial n ohm
Comp Composition P pica ( 10-12)
DCb Deposited Carbon PM Paper, metal cased
POlY Polvstvrene
ETB Electrolytic, tubular
. .
I-r micro ( 10m6)
f farad ” volt
hy henry Var Variable
k kilo (103) w watt
ww Wirewound
M or meg mega (106) or megohms wwvar Wirewound Variable
m milli (10-3)
TABLE 2. Abbreviations and Symbols.
5-l

REPLACEABLE PARTS MODEL 149 MILLI-MICROVOLTMETER
MODEL 149 REPLACEABLE PARTS LIST
(Refer to Schematic Diagram 13621D for circuit designations.)
CAPACITORS
Circuit
Desig. Value Mfg. Mfg. Keithley
Rating TYPO Code Part No. Part No.
Cl01
Cl02
Cl03
Cl04
Cl05
Not Used
4.7 (If
0.1 @f
20 pf
0.1 llf
Cl06 (60~~s) 0.0082 ,rf
Cl06 (50~~s) 0.0122 uf
Cl07 4.7 pf
Cl08 0.01 tlf
Cl09 0.1 I.rf
Cl10 20 uf
Cl11
Cl12
Cl13
Cl14
Cl15 (60~~s)
Cl15 (5Ocps)
4.7 pf
0.1 pf
0.47 ,lf
0.001 ,lf
0.02 If
0.0047 IJ.f
Cl16
Cl17 (60~~s)
Cl17 (5Ocps)
0.001 pf
w.0047 pf
w.0047 pf
c501
c502
c503
c504
c505
20 pf
20 pf
20 pf
0.01 IJf
20 jLf
C506
c507
C508
c509
w.5 pf
1000 ,lf
Not Used
0.1 pf
Circuit
10 v
400 v
450 "
400 v
100 v
100 "
10 "
1000 "
400 I!
450 v
10 "
400 v
200 v
1000 "
1000 "
100 "
1000 "
1000 "
100 "
600 v
450 v
600 "
1000 "
450 v
600 v
15 "
400 v
ETB
MY
ETB
MY
Poly
Poly
ETB
CerD
MY
ETB
05397 K4R7JlOS
14655 wMF4Pl
56289 TVA1709
14655 wMF4Pl
84171 PE-822J
84171 PE-123.l
05397 K4R7JlOS
72982 811Z5V103P
14655 wMF4Pl
56289 TVA1709
ETB
MY
MY
CerD
CerD
Poly
05397 K4R7JlOS
14655 wMF4Pl
00656 V161
72982 801Z5V102P
72982 841Z5V203P
84171 PE-472J
CerD
CerD
Poly
72982 801Z5V102P
72982 811Z5V472P
84171 PE-472J
ETB 00656
ETB 56289
ETB 00656
CerD 72982
ETB 56289
MY
ETB 14655 PI(M6P5 72699 TDLOOO-15
MY 14655
DIODES
PRS
TVA1709
PRS
81125V103P
TVA1709
wMF4Pl
C71-4.7M
C114-.1M
C8-20~
C114-.lM
C45-.0082M
C45-.0122M
C71-4.7M
C22-.OlM
Cl14-.lM
C8-20M
C71-4.7M
Cl14-.lM
C29-.47M
C22-.OOlM
c22-.02M
C45-.0047M
C22-.OOlM
C22-.0047M
C45-.0047M
C35-20M
CS-20M
C35-20M
C22:.01M
C8-20M
C92-0.5M
Cll-1000M
C114-.lM
Mfg. Keithley
Desig. TYPO Number Code Part No.
DlOl SiliCOll Matched Set 80164 14168~
D102 Silicon Matched Set 80164 14168A
D103 Silicon Matched Set 80164 14168A
D104 Silicon Matched Set 80164 14168~
D105 Selenium PT065 81483 RF-18
~~Nominal value, factory set.
5-2 1068R

MODEL 149 MILLI-MICROVOLTMETER REPLACEABLEPARTS
DIODES (Cont'd)
Circuit
Desig.
DlO6
D107
Dl08
DlO9
DllO
Dill
Dll2
D113
Dl14
D115
D116
Mfg.
TYPO NlXllbf?r Code
Selenium PT065 81483
Selenium PT065 81483
Selenium PT065 81483
Selenium PT065 81483
Selenium PT065 81483
Selenium Bridge ClB 81483
ZenC?L- lNl589 81483
Zt?lle?Z lN715 12954
ZeIler lN715 12954
Selenium PT065 81483
Selenium PT065 81483
MISCELLANEOUS PARTS
Keithley
Part No.
RF-18
RF-18
RF-18
RF-18
RF-18
RF-7
DZ-4
DZ-22
DZ-22
RF-18
RF-18
Circuit
Desig. Description Mfg. Code Keithley Part No.
FL (115~)
FL (230~)
Gl (60~~s)
Gl (50~~s)
Jl
---
52
53
---
_--
---
__-
LL
M
---
---
171/,P
Fuse, slow blow, 1.5 amp, 3 AG (Mfg. No.
31301.5)
Fuse, slow blow, 0.75 amp, 3 AG (Mfg. No.
313.750)
Fuse holder (Mfg. No. 342012)
Chopper, Frequency Doubling
Chopper, Frequency Doubling
Receptacle Assembly, INPUT
Plug, Special, Mate of Jl
Jack, Telephone, DEMOD. TEST (Mfg. No. 275)
Receptacle, Microphone, OUTPUT (Mfg. No.
80-PC2F)
Plug, Microphone, Mate of 53 (Mfg. No.
80-MC2M)
Binding Posts (Z), OUTPUT, black (Mfg.
No. DF21BC)
Binding Post, OUTPUT, red (Mfg. No.
DF21RC)
Shorting Link (Mfg. No. 938-L)
Choke, 200 hy
Meter
Meter Lamp (Mfg. No. 323)
Cord Set, 6 feet (Mfg. No. 4638-13)
75915 FU-8
75915 m-14
75915 FH-3
80164 cv-2
80164 cv-3
80164 12450B
80164 13011B
71002 CS-65
02660 CS-32
02660 cs-33
58474 BP-11B
58474 BP-11R
24655 BP-6
80164 CH-1
80164 ME-14
08804 PL-1
93656 co-5
5-3

REPLACEABLEPARTS MODEL 149 MILLI-MICROVOLTMETER
MISCELLANEOUS PARTS (Cont'd)
Circuit
Des@. Description Mfg. Keithley
Code Part No.
Sl
---
---
s2
s3
---
---
54 Toggle Switch, DPDT, ON (Mfg. No. 20905-FR) 04009 SW-14
Tl Transformer, Power 80164 TR-36
T2 Transformer, Filament 80164 TR-26
T3 Transformer, Chopper 80164 TR-37
Cable Clamp (Mfg. No. SR-SP-1)
Rotary Switch less components, FUNCTION
Switch Assembly with components, Function
Skirted Knob, Function Switch
Rotary Switch less components, RANGE
Switch Assembly with components, Range
Skirted Knob, Range Switch
Rotary Switch less components, ZERO SUPPRESS,
Range
Switch Assembly, Zero Suppress, Range
Skirted Knob, Zero Suppress Range Switch
Skirted Knob, Zero Suppress Set Potentiometer
RESISTORS
28520 cc-4
80164 SW-161
80164 13728B
80164 la-11
80164 SW-96
80164 13727B
80164 la-10
80164 SW-58
80164 13726B
80164 RN-11
80164 KN-17
Circuit Mfg. Mfg. Keithley
Desig. Value Rating TYPO Code Part No. Part No.
RlOl 33 kn
R102 2Mn
R103 47 I~(~?
R104 1 m
R105 3.3 MO
RlO6 1 HT:
R107 22 IC?
R108 3.3 M1
R109 1 It-!
RllO 22 I<<?
Rlll 1 M:
RLl2 200 kc:
R113 100 ki!
R114 100 k:!
Rl15 "1 ti:i
R116 470 kq
R117 333 k?
R118 500 kc:
*?jomi.nal value, factory
lO%, l/2 w
0
l/,, 1 w
lO%, l/2 w
l%, l/2 w
lO%, l/2 w
l%, l/2 w
lO%, l/2 w
lO%, l/2 w
l%, 112 w
lO%, l/2 w
I%, l/2 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
10%, 2 w
set.
camp 01121 EB Rl-33K
MtF 07716 MEF R44-2M
Comp 01121 EB Rl-47K
Deb 79727 CFE-15 Rl2-1M
camp 01121 EB Rl-3.3M
DCb 79727 CFE-15 R12-1M
camp 01121 EB Rl-22K
camp 01121 EB Rl-3.3M
DCb 79727 CFE-15 R12-1M
camp 01121 EB Rl-22K
DCb
DCb
DCb
DCb
DCb
79727
79727
79727
79727
79727
79727
79727
01121
CFE-15 Rl2-1M
CFE-15 Rl2-200K
CFE-15 R12-100K
CFE-15 R12-100K
CFE-15 R12-1M
DCb
DCb
CbVar
CFE-15 Ri2-470K
CFE-15 R12-333K
.J RP5-500K
j-4 1264R

MODEL 140 IIILLI-MICROVOLTMETER REPLACEABLEPARTS
RESISTORS (Cont'd)
Circuit Mfg. Mfg. Keithley
Desig. Value Rating TYPO Code Part No. Part No.
R119
R120
R121
R122
R123
R124
R125
R126
R127
R128
R129
R130
R131
R132
R133
R134
Rl35
RI36
R137
R138
R139
R140
R141
R142
R143
R144
R145
R146
R147
R148
R149
R150
Rl51
Rl52
R153
R154
R155
680 kn
3.33 m
2. 2 M"
62 k!?
100 kr2
1.3 Mri
1 Mn
30 kfi
10 kn
95.3 kc
12
1 kn
111 ?
10 kR
100 kc
10 m
3.33 m
1Kl
333 k<l
100 kn
33.2 kn
9.9 kn
220 kn
100 kn
II%
100 kn
9 kn
10 kn
30 kn
l%, l/2 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
5%, 10 w
lO%, 2 w
l%, 1 w
1%
1%
lf4%, l/3 w
5%
lO%, l/2 "
l%, 112 w
l%, l/2 w
0.5%, l/2 w
0.5%, l/2 w
0.5%, l/2 w
0.577, l/2 w
0.5%, l/2 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 "
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
1%, l/2 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
3%, 5 w
5%, 10 w
JrNominal vali.le, factory set.
WrR129 and R130 are matched to l/2%.
DCb 79727 CFE-15 R12-680K
DCb 79727 CFE-15 RlZ-3.33M
DCb 79727 CFE-15 R12-2.2M
DCb 79727 CFE-15 R12-62K
DCb 79727 CFE-15 Rl2-100K
DCb 79727 CFE-15 R12-1.3M
DCb 79727 CFE-15 R12-1M
ww
WWVar
MtF
ww
Special
ww
Special
63743
71450
07716
80164
10F
WP
CEC
R5-30K
RP9-1OK
R94-95.3K
'.*RlE-18-1
80164
'.+cR18-18-1K
wwenc
Special
ww
Special
camp
DCb
DCb
01686
7010 R105-111
80164 R18-18-10K
01121 EB Rl-LOOK
79727 CFE-15 Rl2-1OM
79727 CFE-15 R12-3.33M
MtF 07716 CEC R61-1M
MtF 07716 CEC R61-333K
MtF 07716 CEC R61-100K
MtF 07716 CEC R61-33.2K
MtF 07716 CEC R61-9.9K
camp
DCb
Special
camp
Comp
Comp
01121
80164 EB Rl- 220K R38- 1OOK
01121 EB RI- 1.5M
01121 EB Rl-150K
01121 EB Rl-150K
Comp 01121 EB Rl-150K
Comp 01121 EB Rl-33K
camp 01121 EB Rl- 3.9K
Comp 01121 EB Rl-3.3K
DCb 79727 CFE-15 R12-1K
DCb 79727 CFE-15 R12-1M
DCb 79727 CFE-15 R12-100K
DCb 79727 CFE-15 R12-9K
WWVsr 73138 A
RP4- 10K
ww
63743 10F R5-30K
Order a8 a pair.