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INSTRUCTION MANUAL
MODEL 420A
LOG N PERIOD AMPLIFIER
MODEL 420A KY.7 n WHIOD AMPLIFIER CONlTNTs
TABLE OF CONTENTS
Page
Section I. Introduction ........................ l-1
Section II. Specifications. ....................... 2-l
Section III. Operation. ......................... 3-l
Section IV. Description ......................... 4-l.
Section V. Maintenance ......................... 5-l
Section VI. Replaceable Parts List. ................... 6-1.
Voltage and Resistance Diagram ...................... 6-9
Circuit Schematic Diagram. ........................ 6-11
WhangeNotice...............................Las t
Page
*If a change in the instrument affects the instructions, the correction is
printed on a yellow sheet at the back of the manual.
0862R i
MXEL &OAICQ nPERIOD&@LIFDB INTFiOIWXIOlV
SECTION I INTRODUCTION
Model &20-A
The Keithley Model h20-A Log n Period Amplifier consists of
a logarithmic micro-microammeter for indication of reactor power
level, followed by a differentiator which indicates the reactor
period.
High level outputs for oscilloscopes and one-milliampere
recorders, as well as 50 millivolt outputs, are provided from
both the micro-microammeter and the period amplifier. One side
of all outputs is at ground, making it convenient to connect
associated equipment.
The features of the Log n Amplifier section include full
scale voltage drop at the input of less than five millivolts,
zero drift of less than 0.05 decade in 2L hours, good accuracy,
and built-in calibration standards, The major panel control
is the OPERATE switchj minor controls are the RECOVER button,
AMPLIF`IER BALANCE, SET lo-7 and SET lo-11 adjustments.
The Period Circuit features quick recovery from overloads.
The controls are the OPERATE-CHKCK oo switch and the SET oo
adjustment.
The power switch is at the right of the meters. The pilot
light indicates that power is on.
FIUUFtE 1. Keithley Model 420A Log n Period Ampllfiar.
0662R
MIDEL 42OA LX4 n PERIOD AMPLIFIER SpEcIFICA!CIONS
SZCTION II SPECIFICATIONS
Log n Amplifier
The current range covered is 10-o to 10'13 ampere and is dis-
played on a six-inch panel meter for maximum readability. Accuracy
is within plus or minus 0.2 decade and the output voltage is 10.7
volts per decade plus or minus 20%. Positive currents only can be
accepted; the output voltage is negative.
Calibration: The calibration is checked at the front panel by
means of a control which selects either of two current sources; lo-l1
or 10-7 amperes, The Log n Amplifier is adjusted to read correctly
by means of screw driver contrcls on the front panel. The current
source consists of a 1011 and a 107 ohm resister and a mercury battery.
Amplifier balance may also be checked and adJusted at the front panel.
Input impedance is decreased to a small value by negative feed-
back. The voltage drop across the input terminals will be less than
five millivolts for any position across the meter scale provided that
the amplifier balance is properly set.
Grid current is less than 5 x 10-lh ampere and will not affect
operation of the instrument.
Recover Switch is located at left side of the panel. Its purpose
is to short out the feedback diode and allow quick dissipation of
snuricus charges which sometimes accumulate on the innut of a micro-
mlcroammeter, or are caused by overloading the input.
Accuracy is within 0.2 decade.
Linear-Log Relationship is within 2% f scale length from lo-l3
to 10-f ampere; within 5% from 10-7 to lo- 8 ampere.
Drift, After one hour warm-up, if the instrument is set on a
lxlF= ampere, the reading will not increase to greater than 1.1
x lo-l1 ampere nor decrease to less than 9 x lo-l2 ampere in the
following eight hours of operation.
75 Volt Negative Output is developed for full-scale meter de-
flection, and 1 milliampere can be drawn without upsetting the circuits.
The 75 volt Output connector is at the rear of the chassis. The connec-
tion details and suitable output attenuators are discussed in OPERATION,
Section III.
50 Millivolt Output is provided for convenient, direct connection
to servo rebalance recorders. The internal impedance is approximately
50 ohms.
1263R 2-1
SPECIFICATIONS MODEL 42OA IM) n PERIOD AMPLJFIER
Response Speed of the Log n Amplifier depends upon the current
being measured, upon the capacitance of the external input circuitry,
and upon the setting of the DAMPING control at the rear of the chassis.
Because of the method application of the negative feedback, the slowing
effects of capacitance from the high input terminal to ground have been
greatly reduced, but are still significant. The DAMPING control varies
the response time over a ten-to-one ratio. Table I, below, gives typical
response speeds; via: the tirre of 90% response to a step function with
the DAMPING control set at its minimum position.
TABLE I
RISE TIME - to 90% of final current
Current change, With no significant With SO00 mmf
amperes external capacitance across input
from lo-l3 to 10-l* less than 3 seconds less than 6 seconds
from 10-l* to 10m7 less than 1 second less than 2 seconds
Amplifier Noise is principally power frequency, and isy at most, 2%
of full scale peak to peak at the output terminals, irrespective of the
current range.
Peri~od Circuit
Range covered is from -30 seconds to infinity to three seconds
a single scale.
Accuracy is 3% at 6 seconds.
Speed of Response is three seconds maximum.
Recovery Time is 10 seconds maximum.
Operate-Check oo switch, in the CHECK oo position, removes the
signal from the Log n Amplifier to the Period Circuit. The meter should
read infinity; and if not, the circuit is readjusted with the SET poten-
tiometer. In the OPERATE position, the circuit is normal, with the
Period input connected to the log n output.
10 Volt Output is developed by the period circuit; the voltage is
zero for infinite period, and 10 volts positive for three second positive
period. One milliamm can be drawn. Connection details are discussed
in OPERATION, Section IV.
2-2
MCDEL 42OA Loo n PERIOD AMPLIFIEFI smIFIcmoNs
50 Millivolt Output is provided for convenient direct connection
to servo rebalance recorders. The internal impedance is approximately
50 ohms,
General
Polarizing Potential
.- for ion chambers: +225 volts, connecter is
Amphenol 80-C.
Input Connector is type HN with Teflon insulation, type UG560/U.
High Level Output Connectors are Cinch-Jones tm S202.
Recorder
-- Connectors are Amphenol 80 PC-2F.
Power Requirements: 110 or 220 V. 50-60 cps; 50 watts; unless
specially requested, units wired for 110 volts. See MAIN'FENANCE
section for voltage ccnversion instructions.
Tube Compleonent: FEW 5886, one 6~~6, one 6~~4, one 6~4, two 6~~6,
one 6y6, one lZAUT, two lZAX7, one 12DH7, one OAZ, one W3.
Accessories Supplied: Matchine connectors for all outputs and
inputs, six-foot power cord.
Accessories Available: 4102 Plug-in Input Assembly (replacement
spare).
Cabinet is aluminum, and mounting is standard rack and panel.
19" xmgh x 12" deep, weight 23 pounds.
2-3
MDDEL 420A LOG II PERIOD AMPLIFIER OPNRATION
SECTION III OPEIWLTON
Connect the innut to the ion chamber, and outputs to the recorder
or external indicators as desired.
Turn on power switch.
After a few minutes warm-u turn the OFERATE switch to SET lo-l1
and set the log n meter to lo- lP'with SET lo-11 control.
Check calibration by turning OPERATE switch to 10-T position.
Ad.just if necessary by setting meter to 10-T with the SET 10-T control.
Check amplifier balance by depressing RECOVER switch. Meter
should read lO-l3, If necessary set with AMPLIFIER BALANCE control.
Return the OPERATE switch to OPERATE.
Depress the CHECK infinity switch and set the Period Circuit meter
to infinity with the SET oo adjustment.
Recheck and readjust the calibration of the Log n Amplifier and
SET infinity of the Period Circuit occasionally. These adjustments
should require attention only occasionally after warm-up.
Input Connection
The current source should be connected to the input connector with
the high impedance side of the current source associated with the central
conductor of the connector. The lead-in cable should be polyethylene,
polystyrene, or teflon insulated coaxial cable, and the connector should
have teflon insulation.
Amphenol S2-8Ok is recommended for large cables, type 82-816 for
small cables. During preparation of cable and connectors, it is essen-
tial that all high impedance surfaces be kept scruplously clean to avoid
lead-age. With graphite coated cable, it is necessary to avoid track-
ing graphite onto the high impedance surfaces of the out end of the
insulation and the teflon surface of the connector, Movement of the
cable during measurement should be avoided since this will cause spurious
input signals, because of capacitance changes and generation of static
charges.
066211 3-l
OPERATION MDDNL 42OA Lot) n PERIOD AMPLm
Recording. The Log n Amplifier and Period Circuit both have
two outputs: one for 50 millivolt recorders, and the other for
auxiliary panel meters of controls.
50 millivolt recorders are plugged directly into the 50 milli-
volt output connectors. Both 50 millivolt connectors are Amphenol
SO-PC2F. The internal impedance is approximately 50 ohms. Resistor
dividers for more sensitive recorders can easily be made at the
recorder input.
The Log n high-level output is aero volts for lo-13 amperes and
75 volts negative for 10-6 ampere. One milliampere can be drawn.
The connector is Cinch-Jones S202.
The Period Circuit high-level output is zero volts for infinite
period and 10 volts for 3 seconds period. One milliampere can be
drawn. The connector is Cinch-Jones S202.
Alarm and remote indicating circuits can easily be connected to
the high-level outputs. Amplifiers and cathode ray oscilloscopes are
also connected to the high-level outputs. Terminal #l of each connec-
tor is at ground potential.
+225 bits. A connector has been mounted on the back face of
the chassis to provide +225 volts for polarizing an ion chamber. The
potential is derived directly from the electronically regulated power
supply. The chassis connector is Amphenol 80-C; 80-M is the mat$ng plug.
The Speed of Response, or the time constant of the ion chamber and
micro-microammeter, depends upon the speed of response of the circuitry
of the instrument and also upon the capacitance of the current source
and its connecting cable. Because of the way the negative feedback is
applied in the Log n Amplifier the external input capacitance is not
nearly as important as in the older systems using a voltmeter across a
shunting resistor or diode, and quite large capacitances can be toler-
ated without having an impossibly slow response. Thus, a cable run
from an ion chamber to the micro-microammeter is permissible.
Variable Damping of the Log n Amplifier is provided by the poten-
tiometer on the back face of the chassis adjacent to the input connector.
Maximum damping is obtained by rotating the control fully clockwise.
The damping slows the response of the micro-microammeter so that it tends
to average the statistical noise of the ion Ohamber current and the
noise generated in the input &able, so that when the micro-microammeter
output is dif,ferentiated in'the Period Circuit, false short periods will
not be indicated.
3-2 0662R
MODEL 42OA LOS II PERIOD AMPLIFIER DESCBDTION
BECTION IV DESCRIPTION
Circuit Description - Log n Amplifier Sect+
The Circuit schematic diagram, DR 11737-C, is included at the
back.
The logarithmic scale of the micro-microammeter is obtained by
negative feedback from output to input through a diode whose emission
is limited by negative plate-cathode voltages. The diode used is the
grid-filament structure of a type 5886 electrometer tube.
The 5886 offers outstanding advantages in this application:
(1) The insulation of the grid is of a very high order since the
5886 is an electrometer tube. Therefore the diode plate has very little
leakage which would cause erratic effects in the low current region.
(2) The grid and filament in this tube are extremely small, so
that capacity across the diode is minimal, This results in a consi-
derable improvement in response speed over instruments which employ
more conventional diodes.
The diode used for feedback is V-l, type 5886. The grid is used
as the diode anode and the filament as the cathode, Rl06 is placed in
series with the grid to protect the tube.
The filament circuit voltage is regulated by transistor QlOl con-
nected as an emitter follower. The Zener Diode, ZDlOl, provides the
reference potential.
Rlll is a 200 ohm, ten-turn potentiometer in series with R107
which provide a voltage drop of 2.5 volts. The feedback from the out-
put is connected at this point so that variation of Rlll will contrcl
the potential in series with the output. This potential is necessary
to buck out the voltage across the diode in order that the micro-
microammeter output can be kept at ground potential when the input is
at ground potential.
The calibration circuit consists of a mercury battery, (Rtd&OlR),
and resistors RlOl, R102, R103, and RlOh. The OP RATE switch is used
to select the desired signal, either lo-11 or lo- 9 ampere, With the
RECOVER switch depressed, the log diode is shorted out. In this condi-
tion the logarithmic characteristic of the amplifier is removed and the
circuit is simply a linear feedback amplifier whose zero corresponds to
the lo-13 position on the meter. The AMPLIFIER BAL screw driver poten-
tiometer adjusts the amplifier zero. With proper balanoe of the ampli-
fier, dc voltage at the input will be less than 5 millivolts in normal
operation.
0662~ 4-l
DT!scRIpp10N MDDRL 42OA Loo II PRRIOD AMPLIFIER
The meter calibration is established by alternating between he
lo-11 and 10-7 positions of the OPERATE seitch, which causes 10' lf or
lo-7 ampere to flow in the input. The corresponding potentiometers
are adjusted until these calibration signals read properly on the meter.
The SET lo-11 control adjusts the buck-out voltage in series with the
diode and thus sets the static resistance of the diode at one point, while
the SE 10m7 controls the gain of the amplifier apd thus adjusts the
change of the diode voltage with current, so that the rest of the scale
reads correctly. Once these adjustments are made only the SET lo-11
control needs to be used to compensate for diode drift. The other con-
trols will require infrequent adjustment,
The RECOVER switch shorts out the diode and allows the circuit to
recover quickly from large overloads.
Cl02 is the damping capacitor which slows the response of the micro-
microammeter. With the low impedance end of Cl02 connected to ground,
the response is damped the least. As more and more feedback signal
from the output is introduced at the low impedance end of C102, the damp-
ing is increased. R115, the DAMPING control, increases the feedback
voltage until the desired amount of damping is obtained.
The amplifier of the micro-microammeter consists of two 5886 elec-
trometer tubes, V-2 and V-3, followed by V-L and V-5, high gain pentodes,
operated as a long-tail pair. Feedback from the cathodes of V-h and V-5
to the screens of V-2 and V-3 stabilizes the plate potentials of V-3 and
V-Ii. Additional gain is provided by V-6a. V-7 is a constant-current
coupling element between V-6a and V-6b, which is the cathode follower
output for the Log n Amplifier. The constant-current coupling element
eliminates attenuation so that the output will develop - 75 V for full
scale. The output drives the diode feedback circuit, the panel meter,
the high level and 50 millivolt outputs lus the Period Circuit. The
circuit output potential s zero for lo- P3 ampere meter indication, and
negative 75 volts for 10 -i ampere indication. The 50 millivolt output
is supplied through a resistive voltage divider.
The open loop gain of the amplifier is approximately 10,000; the
feedback factor is approximately 1000.
Cirouit Description - Period Seotion
The period circuit is an operational amplifier connected as a quasi-
differentiator. C201 is the differentiating capacitor and R202 is placed
in series with the capacitor so that response to very high frequencies
is lessened. R2O7 is the feedback resistor and determine the sensitivity
of the period amplifierr R207 is returned to the wiper of potentiometer
R2lo so that the feedback fraction can be varied. In this way the cali-
bration of the period circuit may be adjusted. Capacitor C2Oh slows
the circuit response to about 1 second full scale. If faster or slower
response is desired, C2Oh may be varied accordingly.
0662R,
EiDDNL
42OA LOGn PERIODAMPLIFIER DESCRIFTION
The amplifier consists of balanced 5'886 tubes followed by a
12AU7 tube connected as a differential amplifier. Feedback from
the l2AU7 cathodes to the screens of the 5886 tubes stabilizes the
operating point of the 5886 tube plates. Vll, a cathode follower,
drives the output meter and feedback loop. The open loop gain of
the amplifier is approximately 200. The circuit output is 10 volts
for a positive period of 3 seconds.
Check infinity switch SWj, in the check position, grounds one
terminal of C201 and leaves the grid of ~8 only with the feedback
resistor connected. This condition corresponds to infinite period
or no change in output from Log n Amplifier. If the period meter
does not point to infinity in this position, it may be adjusted by
R20h, the set infinity control on the front panel.
ZD 201 and 202 are Zener diodes connected back-to-back to limit
the amplifier input voltage in case of overload. Substantial decreases
in recovery time is provided by these diodes.
Circuit Description - Power Supple
The Model h20-A utilizes an electronically regulated plus 225 volt
supply and a VR tube regulated minus 150 volt supply.
'phe electronic&iy regulated supply utilizes a type 6~6 series
tube (Vl3) which Is controlled by a two stage differential dc amplifier
(V14 and Vl7). VlT ccnqparee the B plus voltage, sampled via R312 and
R315, to the vol-e of reference tubs V16. The output of V17 Is sqp-
lified by Vl4 and used to control the reslstame of the series tube V13.
The unre@ated B supply is derived frcm full-wave rectifier VI.2 and a
conventional F6 filter netmrk. The minus supply Is derived from a half-
wave rectifier SR2, 3, 4, 5 and filtered with a three stqe RC filter,
R304, 5, 6 and C303, 4, 5 aud finally regulated at minus 150 volts by
v15. The polarizing potential which appears on the back of the chassis
is taken directly from the +225 v0lt supply.
Unless otherwise requested, instruments are supplied wired for
110 v 50-60 cps power line operation. See schematic diagram for
instructions for conversion to 220 volt operation.
0662R 4-3
MODEL 420A Lot n PERIOD AMPLIFIER MAINTENAECE
SECTION V - MAIBTELNANCE
The Keithley Model 420-A Log n Period Amplifier has been designed to give
long, trouble-free service. High quality components have been used throughout,
and the circuits are stabilized by a substantial amount of negative feedback.
DR U737-C, at the back, is the detailed circuit schematic diagram of the
Model 420-A. The circuit operation was discussed in Section IV - Description.
Vacuum tubes V-2 and V-3 are two electrometer tubes and are located in an alum-
inum can which plugs onto the top of the chassis near the input terminals. These
tubes have been selected, matched and labelled; V-2 and V-3 are Keithley parts
~~5886-8. It is reconnnended that the complete input tube assembly, Model 4102,
be kept on hand for replacement purposes.
Vacuum tubes v-8 and V-9 are also Keithley parts ~~5886-8 in a Keithley Model
4102 input tube assembly.
Feedback diode V-l is a Keithley part EV5886-6 which is tested for its logarith-
mic characteristic. Use normal electrometer tube care in handling the tube so
that the glass at the press wKU not become contaminated.
INSULATION: All insulation for the high impedance conductors is made of
teflon, as are the contact insulators on the range switch. This should give
satisfactory service in all humidities. Occasionally, the high impedance insul-
ators should be inspected to insure that they are free from dirt and dust, and
brushed off if necessary.
CONNECTORCAP: The cap for the input connector should be kept in place
whenever the connector is not being used. In storage and in transport, it keeps
the insulation Pmm accumulating dust, dirt and moisture. Before screwing the
cap back onto the connector, be certain that it is clean, so the insulation will
not be contaminated and so that a low impedance bridging conductor will not be
formed between the high impedance contact end the grounded cap.
Reference Voltage Battery: Bl should be replaced once yearly.
Calibrate Period: If period calibration is to be checked, a teat set-up
as described below will be satisfactory:
0762R 5-l
il
MAINTENANCE tam 42OA UN n PERIOD AMPLIF-l.ER
To simulate the exponential change in reactor power level, a
capacitor discharge may be used to set up an electrical analog.
The voltage discharge may be converted into a current by using a
HI MEC resistor to connect the capacitor into the Log n Amplifier
input as shown in Figure 2.
MDDEL
420A
FIGURE 2
The period circuit, if correctly calibrated, should read directly
the time constant of the RC network (RlC) as C is allowed to discharge
through Rl when the key is opened. With a 100 v@t source when the
key is closed, the Log n Amplifier will read 10' ampere, When the
key is opened, after an initial transient, the period circuit should
read RlC. In practice C should be 1 to 10 microfarads and R varied
to give various period readings. A time constant or period of six
seconds is a convenient calibration point, With the values shown,
the period,indication will be accurate from a current reading of about
5 x 10m9 to about 10-l' amperes and any period calibration should be
made while the current is in this range.
Be sure to note that since the instrument can only be calibrated
on negative period with this arrangement, the meter leads of the period
meter should be reversed for this calibration.
The CALIBRATION PERIOD potentiometer is mounted on the chassis
immediately behind the period meter.
5-2 0662R
MODEL
k?OAJJX nPERIODAMPLIFIER
SECTIONVI. REPLACEABLE
PAR%3
LIST
HOW'x)ORDERPAR!lB. Order ccn@onent parts directly from the manufacturer or
from Keithley Instruments, Inc. Order all structure1 parts from Keithley.
The Replaceable Parts List gives the cods number of the component's manufact-
urer in the MlW. CODEcolumn. The neme and address of the nuwrufacturer hav-
ing the code number is listed in the Manufacturers Code Definitions Table
immediately following the Replaceable Parts List. When ordering from ths men-
ufacturer, purchase only quality components meeting the listed specifications.
When ordering from Keithley Instruments, give a description of the part being
ordered, the circuit designation, the Keithley part number, the instrument
model number, and the instrument serial number. Send to:
Order Service Department
Keithley Instruments, Inc.
I.2415 Euclid Avenue
Cleveland 6, Ohio
a Anperes n Ohm
Cer Ceramic Disc P Pica (lo-&)
CerV Ceramic Variable PST Polystyrene Tubular
Camp Composition
compv Composition Variable R Resistor
DCb Deposited Carbon SW Switch
Ex2 Electrolytic Can M MICRO(1.045)
ETB Electrolytic Tubular
V volts
f Farad Var Variable
K Kiln (103) Watt
Elw Wire Wound
m Milli (m-3) WWVar Wire WoundVariable
M Mega (IL+)
MY w--
0662R 6-1
MODEL420A Loo n PERIODAMPLIFIER RNPLACFIABLE
PARTSLIST
cAPAC1mRs
circuit Keithley
Desig. Value Rating Type Mfg. Code Part No.
Cl01 10 pf EbOV cer 19701 c22-100
Cl02 150 Pf 200v PST 00686 c31-150
Cl03 .02 vf Cer oll.21 c22-.02
Cl04 10 pf gq Cer 19-m c22-l.Kl
Cl05 loo Pf Cer 72982 c22-.OOl
cl06 50 fif 6v EC 83125 c17-50
c201 1 Pf MY 00686 c37-1.0
c202 10 pf ii: v" Cer 19701 c22-100
c203 50 llf c17-50
C204 .l bf & : %g: c30- .l
c301 16 Ctf 600V Ex2 14655 ~34-16
c302 loo pf 15 v RrB cll-loo
c3o3 16 Ilf EC FL%2 ~34-16
c304 20 *f g:: EC 37942 c7-20
C305 20 fif 450 v NC 37942 c7-20
~306 .02 pf Cer oll21 c22-.02
C307 .02 vf E:: Car oll21 c22-.02
~308 .l &f 14655 c30-.l
c309 20 pf g:: z 37942 w-20
Circuit Mfg. Keithley
Desig . Description Code Part No.
Bl Battery, Mercury Energizer, 1.34 V, (Vendor No. m42 an8
RM4OlR)
Fl me, 3alW 75915 m.3
Ml Meter, 200 ma 80164 m3
M2 Meter, 200 ma 80164 MEW
Transistor, Genmnlum, 2N365 01295 m5
SR1 Rectifier, Bridge, Single phase, full wave, 20 ma, 73506 1w6
25 V, Selenium
SR2 Rectifier, Half-wave, 65 ma, 1.30 v 81483 ~8
SR3 Rectifier, Half-wave, 65 ma, 130 V
SR4 Rectifier, Half-wave, 65 ma, 130 v FEEi; %
SR5 Rectifier, Half-wave, 65 ma, 130 V 81483 RF~
Tl Transformer (Vendor No. Kl-125) 95333 TN?1
ZDlOl Zener diode, IiN
ZD201 Zener diode, IN469 g$z ::i
ZD202 Zener diode, IN469 99942 DZl
1263R 6-3
REPLACEABLE
PARTSLIST MODEL
42OA LOGn PERIODAMPLIFIER
r3Emmms
Circuit Keithley
De&g. Value Rating 'Pype Mfg. Code Part No.
RlOl CCb 0032-f Rl2-34K
R102 r.m 01661 R12-100K
R103 HiMeg 63060 R20-10"
R104 DCb 00327 R13-10M
R105 camp oll21 Rl-22M
R106 l0KI-l Camp 44655 Rl-1OK
R107 DCb RI%50
R108 g.A DCb ZE RI%150
RlOp WWVar 71450 RP3-100
RllO zz cow OIL21 Rl-680
Rlll 200 n War 73138 ~~4-200
R112 looKn DCb 01661 Rl2-100K
Ru3 Eb 00327 RI&300K
Rl14 z?n* WWVar RP3-UC
Ru5 3m WWVar :g m3-3
R116 1.5 n-i DCb 01661 Rl2-l.r(
RU7 250 n ww R&10-250
Rl.l.8 200 n Var ;:g: ~~3-200
RJJ-9 150 cl ww 77764 R18-10-150
RI.20 22.5 m ww 63743 ~5-22.5~
R121 22.5 m ww 63743 R5-22.5K
RI.22 6~n SCb 01661 R13-6M
~123 loM0 DCb 00327 R13-10M
~124 lolm cow 44655 Rl-1OK
RI.25 u)Mn DCb 00327 R13-10M
Rl26 6mKn Deb Rl2-@OK
R127 10 m DCb RlZ-lOK
~128 220 ul KCb R12-220K
RI-29 470 Kn DZb RU-470K
R130 1.14 Ml DCb R12-1.&l
R131 1.4 Mn 01661 RI&l&J
R132 6oKn zt 00327 RI&6OK
R133 l.ooKn camp 44655 R2-100K
R134 1.5 hcl DCb 01661 RI&1.5M
R135 50 Kn Deb 00327 Rl2-50K
~136 250 KS-I ICb ol661 RI&250K
Rl37 ?N K&-l DCb 01661 ~12-250~
~138 22.5 Kn ww 63743 R5-22.5X
IZb 0032-f Ru-375K
sz ::5KF? Eb 01661 m-2-7%
R141 wn Deb 00327 RI&50
6-4 0662R
MODEL
b2OALCUnFERIODAMPLIFIW ItJmAcEABLE P&m3 LIBT
Circuit Keithley
Desig. Value Type Mfg. Code Part No.
R201 22 Mn Camp olal.21 RI.-22M
R202 6ooIQ-I Eb 00327 RL?&OK
~203 250 n ww 77764 R184.0-250
~204 200 n WWVar 71450 ~~3-200
~205 150 n biw 77764 R18-10-150
~206 47 M camp Rl-47K
R207 5.25 m Eb R13-5.2M
R208 22.5 Kn ww ~5-22.5~
R209 22.5 m ww ~5-22.5~
R2lO 6~ Deb R13-6M
R2l.l ImKn Eb 01661 R12-lOOK
R2l2 10 Mn DCb 00327 R13-l.OM
~213 10 Mn Eb 00327 Rl3-lOM
R214 3.4 Kn Eb Rl2-3.4.K
R215 loo Kn rm Z: Rl2-1WK
~216 Eb 01661 RI&l&l
R217 20% DZb 00327 RX&OK
~218 1.5 MO DCb 01661 Rl2-1.5M
R219 22.5 M ww 63743 ~5-22.5~
R220 1lU-i Eb 00327 Rl2-IX
R221 WWVar 71450 m3-Y(
R222 xi LCb 01661 RIZ-Q(
~223 l.oKn DCb 01661 RE?-lOK
R224 50 n Eb 00327 Rl2-50
~225 55 Kn n;b 01661 ~12-5%
R301 loo n ww 44655 R4-l.OO
~302 loo n camp olJ.21 Rl-100
conlp OIL21 Rl-100
:$a E5nKn ww R5-1.25K
R305 1.25 m-i ww k$1: Rb-1.25K
~306 1.25 IU-I ww 63743 ~4-1.25~
R3o? 5m ww R4-5K
R308 3.3 M-I camp E:: g-p&-M
R309 68Kn camp OIL21
R310 2.2 Mn Eb 00327 Rl2-2.2M
R3u 2.2 MC LCb 00327 Rl2-2.2M
R3I-2 1Mn Eb 01661 RlZ-IM
R313 1l.m ECb 44655 Rl-lM
R314 1.3 Mn Eb 01661
R315 6ooM DCb 00327 ;g:&g
0662R 6-5
RBPLACUBIXPARTSLIBT MDDEL420A Loo n PERIODAhmmlER
Keithley
Circuit Desig. Mfg. code Part No.
Vl 80164
v2 80164 ",',Ez-ii
V3 80164 g&u@&:"
v4
V5 z% EecB6
v6 a6684
V7 i%z7
Va ii m5886-a
VP EV5aa6-8
VlO 73445 EVl2AU7
Vll a6684 Ev6c4
VI.2 58854 EV~BW~
V13 24446 Ew6Y6
v14 73445 mm7
V15 73445 EVOA2
~16 73445 wm3
V17 73445 Ev1zAx'I
6-6 0662R
MODEL
42OA LOGn PERIODAMPLIFIER REPLACEABLE
PARTSLIST
MANOFA!XUREW
' CODEDEFRiITIONS
00327 Welwyn International, Inc. 71450 cm Corp.
Cleveland, Ohio Elkhart, Ind.
00686 Film Capacitors, Inc. 72982 Erie Resistor Corp.
New York, N. Y. Erie, Pa.
ol.l.21 Allen Bradley Co. 73138 Helipot Division of
Milwaukee, Wis. Beckman Instruments, Inc.
FulJ..erton, Calif.
01295 Texas Instruments, Inc.
Transistor Products Div. 73445 Amperex Electronic Co, Div. of
Dallm, Texas No. American Philips Co., Inc.
Hicksville, N. Y.
01661 Wilrite Products, Inc.
Cleveland., Ohio 73506 Bradley Semiconductor Corp.
Hem&an, Conn.
14655 Cornell-Dubilier Electric Corp.
Newark, N, J. 75915 Littlefuse, Inc.
Des Plaines, Ill.
19701 Electra Mfg. Co.
Kansas City, MO. 77764 Resistance Products Co.
Harrisburg, Pa.
2444.6 General Electric Co.
Schenectady, New York 80164 Keithley Instnmu?nts, Inc.
Cleveland, Ohio
37942 Mallory, P.R. and Co.
Indianapolis, Ind. a0183 Sprague Products co.
North Adams, Mass.
44655 Ohmite Mfg. Co.
Los Angeles, Calif. 81483 International Rectifier Corp.
El Segundo, Calif.
49956 RaJrtheon Co.
Lexington, Mass. 83~5 General Instrment Corp.
Capacitor Division
58854 Sylvania Electric Products, Inc. Darlington, S. C.
Electronic Tubes Mv.
New York 19, N. Y. a66434 RCAElectronic Tube Div. of
Radio Corp. of America
63060 Victoreen Instrument Co. Harrison, N. J.
Cleveland. Ohio
95333 Central Transfomer Co., Inc .
63743 Ward Leonard Electric Co. Chicago, Ill.
Mount Vernon, N. Y.
99942 Hoffman Electronics Corp.
Semiconductor Mvlsion
El Monte, Calif.
0662R 6-7
VOLTAGEAND RESISTANCE DIAGRAM - 420 A
MEAS"REMENT5
MADEWITH"TYM FPOM T"SE PINTO WOUND. CONDlTIONS:
LOG n CiRCUlT ON "AMPLIFIER BALANCE", PERloD CiRC"lT ON `\CHECK c-3: BOTH
OUTPUTS SET TO ZERO.
RESiSTANCE READINGS, ( ), A+?6 IN OUMS; K-,000, M=MEGOHMS.
,4LL REAIJINGS APPROXIMATE.
VIEW IS FROM BELOW CHASSIS.
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