Lambda Electronics 71 User manual

INSTRUCTIONMANUAL
POWERSUPPLY
MODEL____71____ SPEC._______
LAMBDAELECTRONICS CORP.
COLLEGEPOINT 56,N. Y.

INSTRUCTIONMANUAL
FOR
REGULATED POWER SUPPLY
MODEL71
MANUFACTUREDBY
LAMBDAELECTRONICS CORP.
CORONA68, NEWYORK
ISSUE A MODEL NO. 71
1-55-123SERIAL NO.1525

INSTRUCTIONMANUAL
FOR
REGULATED POWER SUPPLY
MODEL71
1. GENERAL DESCRIPTION
1. GENERAL DESCRIPTION.
TheModel 71power supply describedin this manualis
designedfor generalpurpose use inindustry, laboratory,
radiostation andschool to supplypower to electronic and
otherequipment. TheDC output voltages areelectronically
regulated,are practicallyindependent of normal linevoltage
fluctuationsand substantiallyfree from hum and noise. The
high-voltageDC output isconstant (within the specified
limits)from zeroto maximum load andfeatures a continuously-
variable voltage·controlwith anauxiliary vernier-control
for precise voltage adjustment. The DC bias-voltage output
is also continuously adjustable and is closely regulated for
linevoltage variations. The following outputvoltages are
supplied:
Output#1: 0-500VDC, 0-200 MA, regulated.
Output#2: 0-200VDC, 0-50 VDC, bias output. Regulated
for line voltage variation.
Output#3: 6.5VAC, 5A, unregulated.
Output#4: 6.5VAC, 5A, unregulated.
Theeasy-to-read 3-1/2" panelmeters permit monitoring
of output voltage and current. Magnetic circuit-breakers
provideconvenient ACand DC overloadprotection. A time-
delayrelay circuitprotects the tubes duringthe initial
warm-upperiod. Sturdy, insulatedbinding-posts are
providedfor frontpanel connections. A 5651voltage
referencetube insureslong time stability for operation.
Qualitycomponents, conservatlvély rated,guarantee long,
dependabletrouble~free service.
1.

2. ELECTRICAL SPECIFICATIONS:
Input;105-125 VAC,50-60 CPS, 475W (max)
DCOutput No.1; (regulated for lineand load)
Voltage:0-500 VDC (continuouslyvariable)
Current;0-200 MA(over entire voltage range)
Regulation (line); 0.15% or 0.3 volt (whichever is
greater)
Regulation (load); 0.15%or 0.3volt (whicheveris
greater)
InternalImpedence: Lessthan 4 ohms
Ripple and Noise: Less than 5 millivolts rms
Polarity:Either positiveor negative terminal
may be grounded.
DCOutput No.2; (regulated for lineonly)
Voltageranges: Internal Resistance:
a)0-50 VDC(no load) 5,500ohms
b) 0-200 VDC (no load) 25,000 ohms
Currentrange:
Any value of external load impedance may be used
includinga continuouslyapplied low impedance or short-
clrcult.Insignificant interactlonon OutputNo. 1.Short
CircuitCurrent: 9MA (max.)
Regulation (line): Betterthan 0.1%.
Ripple and Noise; Less than 5 millivolts rms.
Polarity:Positive terminalconnected
internallyto negativeterminal of
DCOutput No.1.
ACOutputs (unregulated):
Twooutputs, isolatedand ungrounded. Each is6.5 VAC
at 5A (at 115 VAC input). Allows for drop in connecting
leads.May beconnected in series for 13.0VAC
(nominal)at 5A,or in parallel for 6.5VAC (nom1nal)
at 10A.
2.

AmbientTemperature AndDuty Cycle:
Continuousduty atfull load up to40°C (104°F) ambient.
OverloadProtection:
Externaloverload protectionAC and DCsystems
utilizemagnetic
circuitbreakers. Trip-
Free.Instant manual
reset.Front panel.
InternalFailure ProtectionFuses, access through
rearof cabinet.
InputAnd OutputConnections:
Input8 footheavy duty rubber
coveredline cordwith
integralmolded plug,
rearof cabinet.
OutputSturdy insulated"5-way"
bindingposts, front
panel.
Meters:
OutputVoltage Multi—range 3-1/2"
rectangularvoltmeter
calibrated0-50 VDC,
0-200VDC, 0-500VDC.
OutputCurrent 3-1/2"rectangular
mllliammetercalibrated
0-200MA.
VoltageReference Tube:
A stable 5651 reference tube is used to obtain superior
long—t1me voltage stability.
Time·DelayRelay Circuit:
A 30-sec time delay circuit is provided to allow tube
heatersto cometo proper operating temperature before
high voltage can be applied.
3.

TUBECOMPLEMENT:
TubeType Quantity Function
5R4·GY1 Rectifier
6X4 1 Rectifier
6w6-GT6 ControlTubes
6N0301 TimeDelay Relay
12AX73 VoltageAmplifier
56511 VoltageReference
0A2 1 Voltage Stabilizer
3. MECHANICAL SPECIFICATIONS:
Size and Weight and Finish
Size 13" H x 8-3/4" W x 14-1/2" D
Weight49 lbs.
FinishTwo-tone gray
4.

II.OPERATING INSTRUCTIONS.
MODEL71
1. OPERATINGCONTROLS.
a)The "AC"circuit-breaker is inseries with the AC
lineand controlspower to the supply.When the toggle of
the"AC" breakeris in the"ON" position,the adjacent pilot-
lightindicator marked"AC" is illuminated, theheaters of
allthe tubesin the supplyare energized, anda thirty-second
protectivethermal time·delay relay is setinto operation.
b) The "DC" circuit·breaker contacts are in series
with the plate power relay and controls the application of
platevoltage tothe rectifiers ofthe high—voltage DC and
biassupplies. The“DC“ circuit breaker is interlockedwith
thethermal time-delay relay so that the delay cycle is
completedafter thetube heaters reach operatingtemperature.
Afterthe delaycycle iscompleted the “DC" breaker,when
thrownto the‘DC—ON" position, will apply "DC" power, and
theadjacent pilot—lightindicator will beilluminated. The
"DC"breaker maythen be used in normal switch fashionto
turnDC poweron and off withoutdelay.
c)The "VOLTMETER"toggle~switch connects the
"OUTPUTVOLTAGE" meter to eitherthe "HV" output orthe
"BIAS"output circuitsso that eithervoltage canbe monitored
as desired. The voltmeter circuit is designed so that
switchingfrom biasto high·voltage reading will disturb
neitheroutput voltage.
d) The "HV" control consists of a variable transformer
anda precisionwirewound potentiometer gangedtogether,
andpermits the highvoltage DC output tobe set atany
valuefrom 0to 500 VDC. Thecalibration ofthis control
indicatesthe valueof the DCoutput—voltage andpermits
presettingof the "HV"control beforethe "DC" breakeris
turnedon. Italso provides anindication of the high—voltage
DCoutput whenthe "OUTPUTVOLTAGE" meter is used to monitor
thebias outputvoltage.
e)The "/\HV"control is a wirewoundpotentiometer
permittingvernier controlof the high voltageDC output
for precise voltage adjustment. It has a range of plus or
minus5 voltsand a calibration accuracyof 5%.
f) The "BIAS RANGE" toggle switch provides two ranges
of bias output voltage, 0-50 or 0-200 volts DC.
5.

g) The "BIAS" control is a wirewound potentiometer
whichpermits the biasoutput voltageto be set toany
valuefrom zeroto the maximum outputvoltage ofeither
biasvoltage range.
h) The "OUTPUT VOLTAGE" meter is a 3-1/2 inch panel
instrumentwhich indicateseither the "HV"output or "BIAS"
voltageoutput dependingupon the position ofthe "VOLTMETER"
toggleswitch. Inthe "HV" positionit reads 0-500 VDC full
scale(black numerals).In the "BIAS"position itreads
either0-200 VDC or0-50 VDC (red numerals) dependingupon
theposition of the"BIAS RANGE" switch.
i) The "OUTPUT CURRENT" meter is a 3-1/2 inch panel
instrumentin serieswith the "HV" outputand indicates the
external load current of the high—voltage DC output only.
2. OUTPUT TERMINALS.
a)FRONT PANELTERMINALS:
Theoutput terminalsare sturdy insulated "captive—
head"binding-posts whichcan be used ina number of ways
andare sufficientlysturdy totake a substantial amountof
handlingand abuse. Theywill accept "wrap·around"wire
connections,"alligator clips", bananaplugs, spadelugs,
andwire aslarge as #12 AWG forpermanent feed—through
clamping.The 'HV""BIAS" andeach of the "6.5vAc" output
terminal—pairsare spacedon 3/4 inch centersso that they
willaccept standarddouble bananaplugs.
b) "HV" OUTPUT CONNECTIONS:
Theregulated high-voltageDC output is available
at the front panel terminals marked "HV".
Thepositive connectionis brought out through
thered bindingpost marked "+". The negative connection
is brought out through the black binding post marked "—".
In most applications, it is usual for the negative
terminaletobe atground potential. Insome cases, it may
be desired to place the positive terminal at ground potential.
Stillother applicationsmay require that neitherpositive nor
negativeterminal beat ground potential. In suchcases
whereeither thepositive ornegative terminal is to beat
groundpotential, theappropriate terminal on the panel
should be connected by means of a Jumper wire to the binding e
post,marked "INTGND".
6.

Forminimum outputripple, it is recommended
thateither the positiveor negativehigh voltage DC
outputterminal begrounded.
c)"BIAS° OUTPUTCONNECTIONS:
Theregulated DCbias-output voltage is available
at the front panel terminals marked "BIAS". The positive
"BIAS"connection isinternally tied tothe negative "HV"
connectionand isbrought out through the black binding
postmarked "BIAS+"and "HV-". The negative "BIAS"connection
is brought out through the black binding post marked "BIAS-".
d) AC OUTPUT CONNECTIONS:
TheAC outputconnections marked "6.5VAC 5A"
providetwo independentsources ofunregulated voltage for
vacuum-tubeheater—circuits. Both outputsources are
availableat thefront-panel binding-posts. The AC output
terminals may be connected in series to provide 13.0 VAC
at 5 amperes, or in parallel to provide 6.5 VAC at 10 amperes.
Theschematic diagram onthe panelbelow the AC outputbinding
postsshows theproper connections ofthe terminals for
correct"phasing' ofthese voltages.
_SAFETYNOTICE_
DANGEROUSVOLTAGES EXISTIN THIS EQUIPMENT.
OBSERVETHE USUALSAFETY PRECAUTIONS WHEN OPERATINGOR
SERVICINGTHE EQUIPMENT TOAVOID SEVERE SHOCKOR INJURY.
3. PLACING MODEL71 INTOOPERATION.
a)Both the"AC" and "DC"circuit·breakers snouid be
inthe "OFF"position. The "HV" control andthe "BIAS"
controlshould bein their extremecounter—clockwise positions,
the"/\HV" controlin the centeror "O" position.
b) Plug the power cord into a source of 115 volts AC
50/60cycles.
c)Connect thedesired AC andDC loadsto theoutput
terminals of the supply. Note the schematic diagram on the
frontpanel showingproper phasingof the 6.5 VAC outputs
for series or parallel operation.
d) Throw the "AC" circuit breaker to the "ON" position.
TheAC pilotindicator marked "AC"will be illuminated, and
6.5volts ACwill be present at thefront panelbind1ng·posts.
Thethermal time-delaycircuit will startitS 30·seconddelay-
cycle.
7.

e)After approximately30 seconds, throwthe "DC"
circuit-breakerto the "ON"position. The pilot-light
indicatormarked "DC"will be illuminated,and the internal
plate-power·relaywill close. Ifthe "DC" circuit breaker
is thrown to the "ON" position before the 30 second time
delayhas elapsed,the pilot indicatorwill not light nor
willthe plate-power-relayclose until the time-delaycycle
is complete.
f) After the pilot "DC" indicator 1e illuminated throw
the"VOLTMETER" selectorswitch to the"HV" position. Turn
the"HV" controlclockwise to thedesired DC outputvoltage
as indicated on the "OUTPUT VOLTAGE" voltmeter. The "/\HV"
verniercontrol maybe utilized for precise voltageadjustment.
If an external load is connected to the "HV" output terminals,
theoutput currentwill be indicatedon the "OUTPUT CURRENT"
meter.
g) If use of the "BIAS" output voltage is desired,
throwthe "DC"breaker off, connect the bias-loadto the
"BIAS"terminals, setthe "BIAS RANGE"switch to thebias
voltagerange desired,the "VOLTMETER" selectorswitch
to"BIAS" and the"BIAS" controlto zero. Throw the "DC"
breakeron. Turnthe "BIAS" control clockwiseto therequired
voltageas indicated onthe properred scale ofthe "0UTPUT
VOLTAGE"meter. The"OUTPUT VOLTAGE" metermay be used to
monitorthe biasvoltage, the calibrationon the"HV" control
then serving as an indication of the "HV" output voltage.
h) If it is desired to turn off the DC output only,
usethe "DC"circuit breaker,leaving the "AC" breakerin
the"ON" position.In this manner, the supply willbe in
a standby condition ready for instant use.
CAUTION: Turning the supply on and off rapidly
bymeans ofthe "AC" breaker(with the DCbreaker in the
"ON" position) may seriously damage or impair the life of
thehigh voltagerectifier tube. If less than one minute
elapsesbetween thetime the "AC”breaker is turned off and
turnedon again(the time required for theprotective
thermaltime-delay relayto re—cycle)the "DC" breaker should
be kept in the ”OFF" position for at least 20 seconds after
the"AC" breakeris turned on topermit the rectifier heaters
toreturn toproper operating temperature.
4. OVERLOAD PROTECTION.
a)AC OUTPUTCIRCUITS:
Anoverload orshort circuit of the6.5 VAC 5A
outputcircuits willtrip the "AC" circuitbreaker shutting
off the entire supply. Removing the overeload and turning
8.

the"AC" breakeron again will restoreoperation. If the
supply is off for more than one minute the thermal delay-
relaymay re-cyclebefore DC voltagewill be present at
theoutput terminals.(see CAUTION note in paragraph 3
above).
b) HIGH VOLTAGE DC OUTPUT CIRCUITS:
Anoverload orshort circuit of the"HV" output
willtrip the"DC“ circu1t—breaker releasingthe plate-
power·relayand disconnectingthe plate-voltage fromthe
rectifiertubes ofboth the high-voltage DC andbias supplies.
Removingthe overloador short-circuit and throwing the"DC"
breakerto the"ON" position will restore operation
immediately.
c)DC BIASOUTPUT CIRCUIT:
Thebias outputcircuit is so designedthat it
may be short·circuited for indefinitely long periods of
time without damage to any component or effect on the high
voltageDC output.
5. INTERNAL POWER SUPPLY FAILURE PROTECTION:
a)In general,external overload of the outputvoltage
circuitswill resultin tripping of thecircuit breakers.
Internalfailure ofthe power supply components mayresult
intripping of thebreakers or blowingof the internal
protectivefuses mountedas the rearof the unit. Failure
of F1, the I/2 ampere 3AG "Slo-Blo" fuse, indicates failure
of a component of the bias reference supply. Failure of this
fuse will probably require servicing of the power supply.
Referto SectionIII for maintenance databefore servicing
of equipment or replacement of the fuse.
NOTE: Failure of this fuse will result in removal
of voltage from all DC output terminals.
b) F2, a 10-ampere 3AG "Slo-Blo" input line fuse
locatedadjacent toF1 provides protection againstfailure
of the powerstat TA-1, Lambda Part No. TA-549, and input
wiring.This fusewill also protectthe power supply in
eventthat theunit is accidentally plugged intoa 220 VAC
circuitor intoa DC.circuit. This fusewill not failin
thecase ofoverloads of the DCor AC output circuits.
Thls protection is provided by the circuit breakers.
9.

6. NOISE AND RIPPLE OUTPUT:
Thenoise andripple output ofthe high-voltage
DCsupply shouldbe less then 5 millivoltsrms and the
DCbias supplyless than 5millivolts rms atall voltages
andload conditionswithin the specifications. Measurement
of thls level of voltage may be made with an AC VTVM
capableof reading5-8 millivo1tsrms. Meesurements of
theselow valuesof voltege shouldbe made using ashielded
cableconnecting thepower supplyoutput to the AC VTVM.
It is recommended that either the positive or
negativeterminal ofthe "HV" output be connected by a Jumper
wire to the "INT-GND" terminal for minimum ripple output.
7. INTERNALIMPEDANCE.
a)"HV" OUTPUT:
Theinternal impedanceof the hlghvoltage DC
supply is approximately 4 ohms for DC. A 2 mfd oll-filled
papercapacitor isln shunt with the DCoutput circuit
for two purposes: 1) to maintain this low value of output
lmpedenceat audio, andat lowand medium radiofrequencies,
2) to provide a reservoir to supply transient currents of
shortduratlon havingpeak values greater than200 MA.
Anadditional externalcapacitor shuntedacross
the"HV" outputwill provide even lower ACoutput impedance
andallow evenhigher peaktransient currents to be drawn.
Forlow impedanceto high frequency RF·currents,the common
practiceis touse a mica capacitor shuntclose to the RF unit.
b) DC BIAS OUTPUT:
Theinternal resistanceof the DC bias supply
O-200VDC rangeis approximately 25,000 ohms.For low
impedanceto AC, anexternal capacitor shouldbe shunted
acrossthe "BIAS OUTPUT"terminals. For lowimpedance to
high-frequencyRF currents,the common practice is touse
a mica capacitor shunt close to the RF unit. The internal
resistance of the bias supply 0-50 VDC range is 5,500 ohms.
10.

III.MAINTENANCE
SAFETYNOTICE
DANGEROUSVOLTAGES EXISTIN THIS EQUIPMENT.
OBSERVETHE USUALSAFETY PRECAUTIONS WHEN OPERATINGOR
SERVICINGTHE EQUIPMENT TOAVOID SHOCK ORINJURY.
1. GENERAL.
Undernormal conditionsno special maintenance
of the Model 71 regulated power supply is required except
for occasional tube replacement. In the event of failure,
or inability of the regulated DC output circuits to function
properlya listof typical symptoms andtheir probable causes
is given in paragraph "6" of this section.
2. REMOVAL OF POWER SUPPLY UNIT FROM CABINET.
If tube replacement or servicing of the unit is
necessitated,the power susplyunit mustbe removedfrom
itscabinet. Thisis accomplishedby removing the four
largediameter nickel-platedscrews on the rear face of
thecabinet andsliding the unit out.
NOTE: It is not necessary to loosen any screws
otherthan the fourmentioned abovefor removal of the
supply from the cabinet. At no time should removal of
thepainted screwsin the rearof the cabinet beattempted.
3. SERVICING OF POWER SUPPLY WHEN REMOVED FROM CABINET.
a)Upon removalof the cabinet,all tubesare made
accessible,and tubereplacement is simply accomplished.
6W6-GTtubes andthe 6N030 tubeare securedto their
socketsby means ofspring~type retainerclamps. These
retainingclamps mustbe depressed into and held in a
flattenedposition beforeremoving these tubes.when
replacingthe miniaturetype tubes, theyshould be inserted
intoa pinstraightener before puttingthem into the sockets
toavoid bendingpins. Bentpins create strain onthe glass
baseswith the resultingpossibility of breakageor cracking
intime. Whentubes arereplaced, adjustment of calibrating
potentiometersshould bechecked.
11.

b) 6N030 TIME-DELAY·RELAY:
The6N030 1smost readily checkedunder actual
operatlngconditions. If thepower supply is turned on
froma coldstart, and the "DC"circuit·breaker left in
the"ON" position,the internal plate-power-relay will
c1osewith anaudible click, and the"DC ON"pilot light
lndlcatorwill bellluminated within 30to 45 seconds.
Athigh ACline-voltages, the relaymay close
1nas earlyas 20 seconds, atlow line-voltagesas late
as 1 minute. If the plate·power-relay closes much earlier
than 20 seconds or later than 1 minute from a cold start,
the6N030 should bereplaced.
c)0A2 VOLTAGEREGULATOR TUBE:
Uponplacing theModel 71 powersupply into an
operatingcondition at anysetting ofoutput voltage the
0A2 should exhibit an lnternal pale purple glow. If tube
fallsto glowor appears to flicker,the tube should be
replaced.If thenew tube does notoperate properly,the
circuitvoltages shouldbe checked againstthe circuit
diagram.
d) 5651 VOLTAGE REFERENCE TUBE:
Nospecial checkof the 5651tube is required.
Thetube operatesnormally witha bright orangeglow on the
surfaceof itsdlsc-shaped cathode. If the tubefails to
glowor appearsto flicker, it should be replaced.If
then the fault is not remsved, a voltage check should be
madeof thetube and itsassociated circuits. The voltage
acrossthe 5651 shouldrange between 82 and 92VDC and
should not fluctuate.
4. ADJUSTMENTOF CALIBRATING POTENTIOMETERS R35 & R36:
If any of the tubes other than the rectifiers,
(5R4-GYand 6x4),the series control tubes,(6w6·GT), and
thetime·delay relay,(6N030), arereplaced, the calibrating
andalignment potentiometers, R35 andR36, mayrequire
readjustment.This readjustmentshould be madeaccording
tothe followingprocedure:
a)With ACand DC circuitbreakers in the "OFF"
position,zero-set the "OutputVoltage" and "Output Current"
metersaccurately.
b) Turn the "HV" control to its extreme clockwise
position.The pointeron the controlknob should line up
with the 500 volt callbratlon line or very close to it.
12.

If a major discrepancy exists, loosening of the two set
screwsin theknob will permit readjustment of its position.
c)Set the"/\HV" control toits center or "0"
position.
d) Set the "Voltmeter" switch to the "HV" position.
e)With noexternal AC orDC load on thepower supply,
turnboth "AC"and "DC" circuit breakers onand allowthe
supply to warm up for at least 10 mlnutes.
f) With the "HV" control set to 500, adjust R36 so
thatthe "OutputVoltage" voltmeter reads500 volts (black
scale).
g) Turn the "HV" control to the zero mark. Adjust
R35so thatthe "Output Voltage" voltmeter reads zero.
h) Repeat steps "f" and "g" until the "HV" control
readszero inits extreme counter clockwise positionand
500volts lnits extreme clockwiseposition.
5. OPERATIONAL CHECK.
a)REGULATION WITHLOAD:
Aftertubes havebeen replaced orthe equipment
serviced,a simplecheck of theproper operation of the
0-500VDC output circuit supplymay bemade byalternately
connectingand disconnectinga 200 MAload to the supply
with the 'Output Voltage" meter in the "HV" position.
Except for a transient kick of the meter needle when the
load is connected to the supply, the change in output
voltageshould bebarely perceptable (less than 1/10 of
1division onthe meter scale) for proper operation. An
ACVTVM capableof reading5 millivolts rms maybe employed
tocheck thenoise and ripple leveloutput of the supply
whenmaking thischeck. Shielded leads shouldbe employed
toconnect theAC VTVM to thepower supply outputterminals.
Notethat the"DC" "BIAS OUTPUT"circuit is not
regulatedfor loadvariations. (SeeElectrical Specifications)
b) REGULATION WITH LINE:
A Variac or Powerstat connected between the AC
powerline andthe input to the Model 71may beemployed
tocheck theregulation of the DCoutput circuits.With
the"Output Voltage"voltmeter lnthe circuit being monitored
andthe linevoltage varied from 105to 125 VAC,the change
inoutput voltageshould be barelyperceptible (lessthan
l/10of 1meter division) for proper operation.
13.

6. TYPICALPOWER SUPPLYFAILURE CONDITIONSAND THEIR
PORTABLECAUSES.
SAFETYNOTICE
DANGEROUSVOLTAGES EXISTIN THIS EQUIPMENT.
OBSERVETHE USUALSAFETY PRECAUTIONS WHEN OPERATINGOR
SERVICINGTHE EQUIPMENT TOAVOID SEVERE SHOCKOR INJURY.
Referto theSchematic Diagram for proper
operatingvoltages in theequipment.
It is recommended that the input plug be removed
fromthe 115VAC source whenremoving or replacing tubes.
OPERATINGCONDITION REMEDYOR SOLUTION
a)AC circuitbreaker CheckAC output for overload
trips repeatedly or short circuit. Remove
overloadcondition.
b) DC circuit breaker 1) Check "HV" output load
trips repeatedly circuit for overload or short
circuit.Remove overload
condition.
2),If thisdoes not eliminate
tripping of DC breaker, then
checkfor faulty5R4-GY tube.
This tube should be tested in
a tube checker. If found
faulty,it shouldbe replaced.
3) If tube is found to be
goodor ifreplacement by a new
tube does not eliminate breaker
tripping,check capacitors,
C1and C2Afor breakdown or
shortcircuit. Ifthese are
foundto because of breaker
tripping,replacement ofthese
capacitorsis required.
c)Presence ofhigh DC 1) Shorted6W6-GT tubes,V2
positive voltage at through V6. Shorting of tube
terminals compared to elements within tube envelope
thatindicated on"HV" will resultin lossof control.
dial, along with high A visual inspection of the
rippleand poor individualtubes may lead to
regulation.(no externalidentification of faulty tube.
load is applied to "HV" If this is not the case, each
output.)tube individuallyshould be
removedwhile theoutput
voltageis monitoredon the
"OutputVoltage" meter.
14.

If upon removal of any tube
V2-V6,this condition is
eliminated, replace this
faultytube witha new tube.
2) Filament burnout of 12AX7.
V8.lf tubesV2-V6 ere all
foundto begood, the 12AX7,
V8may havea burned out
filament. This is slmply
checkedfor byreplacing the
l2AX7with anew tube.
3) Loss of bias supply voltage
willresult inrise of output
voltage.If biassupply output
voltageapproaches zero volts,
and5651, V14is extinguished
andvoltage acrossC5A is zero,
thebias supplysystem fuse,
F1,1/2 Ahas failed. Insert
a 1 Ampere AC ammeter in place
of the fuse and turn on the
supply.lf currentexceeds
0.4Amperes check 6X4,V10 for
shortor gassycondition, and
C5A,CSB forshorted capacitors.
If any of these components are
foundto befaulty, replace
thesecomponents.
4) Absence of voltage across
filtercapacitors C5A,C5B.
checkV10, 6X4tube for open
or burned out filament. This
is most simply accomplished by
replacingtube witha new tube.
5) Presence of bias supply
inputfilter voltageand
absenceof supplyoutput
voltagesa) 6W6—GT, V1
filamentis burnedout, replace
tube.
b) Filament burnout of 12AX7,
V12.This iseasily checked
for by replacement with e new
tube.
15.

d) Presence of positive 1) Filament burnout of l2AX7,
lowlevel "HV"voltage as V11. Thisis easily checked
comparedwith thatby replacement with anew
indicatedon the"HV" dial, tube.
poorregulation andhigh
ripple.(no external load2) Check voltage across
appliedto "HV"output.) capacitor, C2A forvoltage
conditionsspecified on
schematicdiagram. Iffar
belowindicated voltage,check
filtercapacitor foropen
circuit.
3) An abnormal increase of
referencesupply voltage
resultsin reducedpower
supply "HV" output voltage.
Highbias supplyvoltage with
associatedhigh reference
supply ripple voltage. This may
be the result of internal grid
tocathode orscreen grid short of
6W6-GT,V1. Replacewith a new
6W6-GTtube.
4) Burnout of V8, 12AX7 will
causethe biasvoltage to rise.
It will have a similar effect
onthe "HV"supply of greater
magnitudein the "HV"supply.
Thereforethe netresult of
filamentburnout of thistube
is a rise of "HV" voltage.
e)Apparent satisfactory6W6-GT tubes, V2through V6,
operationat 200MA loadexhibit poor cut-off
with rise of ripple voltage characteristic. To check
at zero external load. cut—off characteristic,
operateat zeroload and low
"HV" output voltage. Monitor
the"HV" outputwith a VTVM
or high impedance AC voltmeter.
Removeone tube ata time
untilfaulty tubeis identified.
Faultytube isidentified by
returnto normalof "HV"
outputripple voltage.Care
should be exercised in
handling6W6-GT tubes to
preventburning of handsdue
totouching hotglass envelope.
In removing 6W6-GT tube,
depressretaining clamp
maintainingthis positionof
theclamp whiletube is
removed.
16.

f) Apparent satisfactory 1) Faulty 6W6-GT tubes, V2
operationat lowcurrent through v6, willcause
valueswith supplyfailure remaining6W6-GT tubes to
at 200 MA external and carry excess load. Tubes
105line. shouldbe visually inspected
for filament burnout. If
burnoutis notapparent, then
tubesshould bechecked on
a tube checker.
2) Faulty 5R4-GY, V9,
rectifiertube. A similar
conditionapplies tothe 5R4-GY
rectifier.If tubedrop is
excessiveunder load,then
operationat 200MA andat
105VAC linewill be impaired.
Thetube shouldbe checked in
a tube checker, and if faulty,
itshould bereplaced.
g) Apparent instability Faulty bias and main amplifier
lnPower SupplyVoltage, input tubes cause this voltage
drift of order 1 volt wandering. The tubes involved
magnitudeor greater. are12AX7 tubes, V11 and V12.
One tube should be first
replacedand theoutput voltage
monitored.If thiscondition
is not removed, replace the
secondl2AX7 tube.
A schematic diagram of the
powersupply willbe found in
therear ofthis manual. The
diagramcontains typical
operatingvoltages for a
specificset ofoperating
conditions.
Thepilot lightindicator
lampsare NE51neon lamps.
Theyare accessiblefrom the
frontpanel bymerely
unscrewlngthe pilot·1ightdome.
_SAFETYNOTICE_
DANGEROUSVOLTAGES EXISTIN
THISEQUIPMENT. OBSERVE THE
USUALSAFETY PRECAUTIONS WHEN
OPERATINGOR SERVICING THE
EQUIPMENTTO AVOID SEVERE
SHOCKOR INJURY.
17.

7. MAINTENANCE OF THE POWERSTAT ("HV" CONTROL).
a)DETERMINING DEFECTIVEOPERATION:
Whenthe brushcontact of the"Powerstat"
indicatesexcessive wear (lessthan 1/32"of the carbon
brushextends fromthe brush holder)or arcingoccurs when
the"Powerstat" isrotated with a loadon thesupply
resultingin highnoise output from the equipmentor hash
inRF equipmentin thelaboratory, the brushcontact should
be examined. A properly adjusted "Powerstat" shouldnot
arcor sparkunder load when therotor shaft is turned.
If arcing is present, the "Powerstat" should be examined
andserviced.
b) SERVICING THE "POWERSTAT".
The"Powerstat" can beeasily reached by removal
of the cabinet from the power supply. If closer examination
or adjustment of the powerstat is required, greater
accessibilityis realized byremoval ofthe front panel.
This is accomplished.by unscrewing the six large phillips
head screws on the front panel. After removing the six
screws,draw thepanel forward then tiltit being careful
toclear thepowerstat from the frame indoing so. The
powerstatbrush isnow free andclear. If wearis
indicated,replacement ofthe brush iseffected by
looseningthe twoset screwsin the brush holder and
removingthe holder.Care must be exercisedin replac1ng
theholder to insurethe new holder verynearly assumes
itsformer position.
1. DIRTY OR PITTED COMMUTATOR SEGMENTS.
Dirtyor pittedcommutator segmentsmay
be cleaned with carbon-tetrachloride.and/orsanded
lightlywith finecrocus-cloth. Excessively pitted
commutatorsegments area result of failureto replace
a worn brush or severe overload of the "Powerstat".
Replacementof the entire"Powerstat" assembly may
be necessary. (See paragraph 8a) Refer to Lambda
PartNo. TA-549when ordering.
8. SERVICENOTES.
a)REMOVAL OFTHE "HV" POWERSTAT ANDPRECISION
POTENTIOMETERASSEMBLY.
1. Remove the connections to the powerstat
andthe precisionpotentiometer. Identify
leadsto facilitatereplacement of entire
assembly.
2. Remove the "HV" control knob.
18.