Dynascan B&K 290 User manual

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Deqr Friend:
Congrotulqtions on your purchose of B d K-Precision
Test Equipment, qnd welcome to the B & K Icnnily. We
hope your experience with your new test equipment
will mcke you q lifetime B d K customer.
Your instrument is bocked by more thqn 20 yeors of
experience in designing and mqnufocturing. Our most
importcnt gool is your sqtisfqction. At B & K, test
equipment is mqde to meet the demqnds of the field focusing on dependcbility
qnd qccurqcy. We also concentrqte on simplicity crnd operoting ecse with
feqtures thqt reduce the possibility of humqn error crnd speed the servicing
Process.
In order to determine the type of test units thqt cre needed we hqve been
guided by letters qnd reports from techniciqns ond engineers who use the
equipment doily. Our field tests qnd studies hove helped provide better qnd
Icster service techniques. Close contqct hqs been mqintqined with the mqnu-
facturers of consumer products which our test units will be checking ond
trouble-shooting.
Key personnel in our company cut their eye teeth in the TV service business.
This is why we hqve more "sensitivity" for the problems qnd conditions under
which the test eguipment will be used.
B & K product desigrnscrre constantly reviewed, qnd refinements qre mode
or new models developed to meet crdvqnces in our industry ond to fill your
needs. We set our stqndqrds high so you can be cssured that the B & K test
inskuments you buy represent qdvqnced design, quclity conshuction, crnd
dependcble long-term performonce qt a price you con cfford.
If you hqve qny comments or thoughts qbout our products, or test equipment
in generol, I would be delighted to heqr from you.
Thqnks for your confidence in B d K ond we look forwqrd to serving you for
c long time to come.
Sincerely,
CqrI Korn
President

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TABLE OF CONTENTS
Page
GENERALDESCRIPTION
AND SPECIALFEATIJRES ...... 3
SPECIFICATIONS
OPERATING
CONTROLS
OPERATINGTHEMODEL29O. .,...6
SafetyPrecautions... 6
PreparationforMaking
Meazurements 7
MeasuringDCVoltages... .....7
7*ro Center DCVoltages 7
MeasuringACVoltages... 7
dBMeasurements 8
MeasuringResistances... .....10
MeasuringACCurrent.
. . . . . . . 12
MeasuringDCCurrent.... ....13
MeazuringDCCurrentsbelow
50mA . . . . . 13
CALIBRATION
ANDMAINTENANCE .....14
CIRCI]IT
DESCRIPTION. ..17
WARRANITYSERVICE
INSTRUCTIONS ....19
WARRANTY ....20
3
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OHMSMEASI,JREMENT:
8LnwVoltage
Ranges RXO.I, RXl, RXl0, RXl00, RXIK, RXI0K,
(33mV): RX100K,
ru(lM.
7NormalVoltage
Ranges RXl, RX10, RX100,RXIK, RX10K, RXI0OK,
(1.25V): RxlM.
Midscale
Reading: l0 (timesmultiplier)
Accuracy: t3oofarc,
(+4"ofarconRX0.1
and
RXIM ranges). '
DC CURRENT:
10Ranges 50pA,
l50pA,5001rA,
l.SmA,
5mA,l5mA, 50mA,
150mA,500mA
and1.5
Amp
fullscale.
Accuracy: !37ofull scale;
+
4%on1.5
AmpRange.
InternalVoltage
Drop: 50mV
atinstrument
inputterminals,
to 50mArange.
AC CURRENT:
10
Ranges: 50pA,l50pA, 500pA,
l.smA, smA,l5mA,50mA,
lsOmA,50OmA,
and
1.5Ampfullscale.
Accuracy: !4% full scale
@6011z,,
lsvo on 50pA
and1.5
unp
ranges.
Internal
Voltage
Drop: 50mV,
at
instrument
inputterminals,
to 50mA
range.
Frequency
Response: +.5d8,
20llzto 5kHz,
50ouA
to l5&nA ranges.
+3d8,
TlIzto l6kHz,
500uA
to l50mA
ranges.
DECTBEL
(dB):
l0 Ranges:
Accuracy:
Reference:
RESISTORS:
Multipliers:
-40 to+66.
!3Vo
offullscale.
lmWinto
600ohms.
(.775V]_
trLVo
Precision
Type
- Frequency{ompensated.
Current
Shunts: l%Precision
TYPe
Ohms
Shunts
:ZVoPrecision
Type
METER: 7",l001rA,!2Vo,100".
DCzero
center
scale.
Mirrored
scale.

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OPERATING CONTROLS
This ElectronicMultimeter is assimple to operateasaconventional
WVM. The
following is a brief description
of eachcontrol andhow it is used
(refer to Figure
1).
l. METER ZERO ADJUST (MECHANICAL): The mechanicalmeter zero
adjustment must be made before the instrument is turned on. Insert a
screwdriver
(preferably
non-metallic)
into the slotlocated
in thecenter
of the
front panel immediately below the meter face.While gently tappingmeter,
veryslowlyturn themechanical
zeroadjustuntil thepointer restsat zero.
2. FI,JNCTION
SWITCH: Usedto selectthe desired
function for the measure-
mentsto beperformed.
3. RANGE SWITCH: Usedto selectthe desired
rangeof current, voltage, or
resistance
to bemeasured.
4. OFF-ON SWITCHAND ZERO CONTROL: To turn the meter on, pull the
ZERO control shaft
outward.
Theredlampon themeterwill glow,indicating
the meter is ON. Rotate the ZERO control to position the pointer of the
meter at zeroon themeterscale
or to positionthepointer on thezerocenter
when usingthis feature.Push the ZERO control shaft in to turn the meter
OFF.
5. OHMS CONTROL: The OHMS control is adjustedwith the FUNCTION
switch in oneof theOHMS
positions
and
with thetestleadsopen. Rotatethe
OHMScontrol for afull scale
indication, infinity (oo)
on the ohmsscale of the
meter.
6. PROBE SWITCH: This instrument is equippedwith a strieldedtest leadto
allow accurate
AC measurementsin the presence
of strong
electrical
fields.
Whenthe switch is in the 100Kposition,a l00K resistor
isswitched in series
with the test lead. This isolatesthe cablecapacityfrom the circuit under test
when makingDC voltage
measurements
in RF, IF or sweepcircuits. Setthe
probe switch to the DIRECT position for all measurements
other than DC
voltage.
7. ADJUSTABLE HANDLE: The carryinghandle
may be used
to supportthe
instrument in a convenientslopingposition for easy
viewing.The casealso
canbeplaced in eitheraverticalor horizontalposition.
OPERATING THE MODEL 290
SAFETY PRECAUTIONS
A certain amount of danger
is always
present
when working on
electricalequipment and therefore,the user
is cautionedto always
familiarize himself as much as possiblewith the equipment to be
tested,
beforeanywork isperformed. It shouldbekept in mind that
high voltages often appear at unexpected points in defective
equipment.

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d. Set the RANGE selectorswitch fully clockwise andconnectthe test leads
to
the circuit the sameas
for DC voltage
measurement.
e. Observethe meter pointer indication on the black scalemarked "O" and
rotate the RANGE switch counterclockwise to obtain the best useable
meter deflection. Positivevoltages
will make the pointer deflect to the right
of the center zero mark. Each side of the scalelepresentsone-half of the
range
being
used.For example,
whenthe .5volt range
isbeingused,
each
half r
of the scalerepresents
.25volt andeach
division.01volt. Thepurpose
for the
center zero scale
is to indicate a balanced
condition. For example,if this
instrument is used in the alignment of an FM discriminator, the desired
balanced
condition will resultin areading
of zeroon themeter.
A misaligned
condition will cause some deflection in either the positive or negative
direction.
4. MEASURING AC VOLTAGES (RIvlS & P-P):
NOTE
Effect of waveform in measuringAC voltages:
This instrument
employs a peak-to-peak
type detector, and is calibrated using a
sinusoidalsignal.The scale
is calibrated to give RMSreadings,
using
effective values basedon a true sinewave.When it is known that
other than sinusoidal
signals
are beingused,
it must be recognized
that the accuracy as specified for sinusoidal waveforms will not
apply. However,peak-to-peak
values
will remainaccurateusingthe
peak-to-peak
scaleson themeter.
a. Setthe FUNCTION switch to the AC V position.
b. SetthePROBE
switchto DIRECT.
c. Setthe RANGE switch to the desired
position. If the voltageis not known,
setRANGE switch fully clockwise.
d. Short test leads
together
and rotate ZERO control until meterpointer rests
over
zeromarkon VOLTS/MA scale.
e. Connect the black (negative)lead of the test lead assemblyto the chassisor
reference
point of thecircuitundertest.
f. Bring the tip of the probe in contact with the point in the circuit wherethe
voltage
isto bemeasured.
g. Observe
the meterindication. RMS voltage
is readon the two redscales
just 6
below the mirrored scaleon the meter.
To measure
peak-to-peak
voltage,
the
two red scalesmarked VOLTS P-P
areused.
The scale readings
aremultiplied
by the same
multiplier factors as
wereused
in DC voltagemeasurements. '1
s. dB MEASUREMENTS:
The dB scale
(-10dB to +6dB) for measuring
output level is calibrated
according to the standard of lmW into 600 ohms and direct scalereadings

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NOTE
ThedBscales
of thismeter
andthechartsin Figure
2 and
Figure
3
only applywhenthe voltage
being
meazured
is a puresinewave.
Complex
waveforms
suchasthose
encountered
in musicmaterial
will not give
a trueRMSreadingfor thedB systemto beaccurate,
however,
the dBscalescanbeused
for relative
level
measurements.
6. MEASI.JRING
RESISTANCES:
CAUTION
When
makingre$stance
measurements
besurethatthepower to the
equipment
under test is disconnected.
If voltageis accidentally
appliedto theohms
ranges,fusereplacement
maybecomenecessary.
a. Hi frms Measnuements.
Tomeasure
resistance,
settheFIJNCTION
switchto
theHI OHMS po$ition,
andtheRANGE
switchto therange
thatwill put the
resistance
to bemeasured
asclose
to the centerof meter
scaleas
possible.
When
the FLJNCTION
switchis placed
in the OHMS functions,
the meter
pointerwill movefrom theleft hand
edge
of themeter
(zero)
to theinfinity
(c) markon therighthand
side
of themeter.
Shorttestleads
together
and
rotateZERO
controluntil neter pointerrests
overzero
markonohms
scale.
Remove
shortfrom testleads
androtatethe OHMS
control to adjustthe
meter
pointerto exactly
theinfinity (o) markon theright hand
sideof the
meter.Besure
that theprobeswitch
isin theDIRECT
position.
When
using
the HI OHMS
function in solidstate
circuits,
theapplied1.25
voltswill be
high enough
to causediodesor transistors
to conduct.On all resistance
ranges,
the probe tip is positive
with reqpect
to the minus(-) testlead.
Remember
this whenchecking
components
which
have
a differentforward
andreverse
resistance
such
assemiconductors
and
electrolytic
capacitors.
b. Cheching for Triggering of Inw-Power Silicon-Controlled Rectifiers
(SCR):Low-power
SCR'scan
becheckedto see
if theycanbetriggered
to
the
ON.condition:
Tomake
this
check,
proceed
asfollows:
(1) Set
theFLJNCTION
switchto HIOHMS
and
the
RANGE
switch
toRXl.
(2) Adjust
OHMS
controlso
meter
reads
full scale (oo).
(3) Set
thePROBE
switch
to theDIRECT position.
(4) Connect
Minus
(-) testleadto thecathode
of theSCRand
thePlus
(+)
testlead
tothe
anode.
(5) If theSCR
isgood, the
meter
willcontinue
toread
o. Nowmomentarily
shorttheSCR gate
lead
to anode
lead.
Themeter
strouldread
averylow
resistance,
in"dicatingthat theSCRhas
beentriggered
and
isconducting.
Removing
voltagefrom theanode
lead
of theSCRwill returnit to the
non-conducting
condition.
c. [.o Ohms
ll{casurements.
TheLO OHMSfunctionisused
to makeresistance
measurements
in solidstate
circuits
when
theforward
conductionof adiode
or transistor
junction cancause
an objectionable
error. Whenusingthis
I
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(3) Connect
a short
heavy
gauge
wirebetween
theplusandminus
jacks
and
adjust
ZERO
control
until pointer
rests
exactly
over
zeromarkonOHMS
scale.
(4) Removeshort
from test
jacks.
The.meter
pointer
will move
fromthe
left
hand
edgeof themeter
(Zerc)toward theinfinity (oo)
mark
ontheright
hand
side
of the meter.
Rotate
theOHMS
control
to adjust
themeter
pointer
toexactly
theinfinity mark.
(5) Repeat
ZERO
and
OHMS
adjustments
atleastone
moretimeto obtain
thebest accuracy.
(6) Makesolid
connections
between
test
jacks
and
devicebeing
measured
and
readresistance
on OHMS
scale
(if device
hasnoleads,use
short
heavy
gauge
wire).
(7) Multiplyresistance
reading
by 0.1.For example,
if themeter
reads
l0
ohms
(center
scale)
the resistance
beingmeasured
will be l0 x 0.1= I
ohm.
NOTE
It will benecessary
to readjust
theOHMS and
ZERO
controls
when
returning
to thehigherOhms
ranges.
e. Measuring Resistance
of Thermistors:The I.o OHMS function strouldbe
used
for making accurate
measurements
of resistances
of thermistors
of low
resistancevalue.
If this measurement
is made
in the HI OHMS
function,a
changtrg
resistancereading
will resultdueto heatingcaused
by thehigher
current
flow through
thethermistor.
The
thermistorstrould
notbe
held
in the
hand and shouldbe kept awayfrom any other heatto obtain the most
accurate
fesistanceindication.
7. MEASI,JRING
ACCI.JRRENT:
a. Set
theFUNCTION
switch
to theACA position.
b. Set
thePROBE switch
to DIRECT.
c. Shorttestleadstogetherand
rotateZERO controluntil meter
pointerrests
overzeromark
onVOLTS/MAscale.
d. Set
RANGEswitch
to the desired
range.If theapproximate
value
of current
flowingwithin thecircuitisnot known,set
theRAf.lGEswitch
to the l.5A
positionandwork down toward
the50pA range
until anaccurate
reading
is
obtiined.
e. Turn the powerto the equipment
undertestOFF andopentheciicuit in
'whichyou wistr
to measure
current
flow.Connect
theground
lead
of thetest
lead
assembly
to oneside
of thecircuit.Connect
thetip of the
probe
to the
otherside
of thecircuit
under
test.
f. Turn the power to the equipmentunder test ON andobserve
the meter
pointer deflection.Set the RANGE switchto obtain the most accurate
indication
(nearest
to full scale).
ACcurrent
isread
onthetworedscales
just
belowthemirrorscale
onthemeter.
t2

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:INSUUnC JO CNIUOSVSW '8

CALIBRATION Af.{D MAINTENATICE
The catbration, bias and balance adjustments have been carefully and
accurately adjusted at the factory, and they should not require readjustment
unless components have been replaced or these adjustmentshave been dis-
turbed. If, for any reason,recalibration becomesnecessary,
carefully perform
the following proceduresas required.
CALIBRATTON OF THE 29O (SEE FTGURE. 4 FOR ADJUSTMENT
LOCATIONS): To gain access to the calibration adjustments it will be
necessaryto remove the back from this instrument. To remove the back
cover, remove the two (2) screws located at the bottom rear and the two
(2) screwsat the rear near the top of the cover. After the screwshave been
removed, tilt the bottom part of the back cover outward (away from rear of
unit) allowing the line cord to slide through opening and then gently lift the
back cover up and away from the top portion of the front panel.Adjustments
must bemadein the order indicated below:
BIAS ADJUSTMENT: Connect an external voltmeter between * meter
terminal and common ground (foil ground, common jack, etc.). Set the
ZERO control so meter pointer restsoverzeromark on VOLTS/MA scale.
Adjust Biasadjustment
(R53) so
that external
meter
reads
6.5volts.
Itr0
CAL
crL
R39
r,
,'
.ry
fi)c
CSIJ
R46
-DC
CAL
R45
BIIS
AD''
R53
AD'
R51
RI
. (Racessed
Contrcl)
r USE TLIGIilENT IOOL OR EIN BIIDE
SCREIIDRIVER !O I,IAXE gIS IA'US$,IErIT
Figurc 4. Adiu$mcnt locotionr
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Sumogo;eql u!?lqoot les eq lsnu luaulsnfp? ocwpq eql rflCN;H;

REMOVING THE INSTRLJMENT
FROM ITSCASE: To gain
accessto theprinted
circuit boardand for general
servicing,thecase
(endpieces)
mustberemovedfrom
the front panel.
To remove the case, first remove
the cover
(see
instructionsunder
"Calibration
and Maintenance").Next, removethe two screwsfrom the tie bar locatedat the
top rear,
just abovethe meter.Rotate the handledown towardthebottom rearof
the instrument. Gently pull end pieces
outward (sideways)
and awayfrom front
panel.
Lift endpieces
up and away
from front panel.
To remove
theprinted circuit boardfrom the front panel,proceed
as
follows:
l. Removethe two (2) screwsat the bottom rear of the unit that holds the
transformer
bracket
in place.
2. Remove
the two (2) laryecontrol knobs
andcontrol nutson the front panel.
3. Slide thetop portion of themeterback
(away
from front panel).
4. Remove
the two (2) largemeter retaining
nutslocatedat approximatelythe
centerof the P.C.
Board.
5. Remove
the meterfrom the front of the P.C.
board.
Sufficientlead lengthis
provided
to allow servicing
of theP.C.
boardcomponents.
OVERLOAD PROTECTION: This instrument is protected against accidental
overloads
on all functions and all ranges.
The voltageranges
are
protected
because
the high input impedancelimits the amount of voltageand current applied to the
gate
of the FET. On the resistance
andcurrent
functions,the fuse
Fl anddiode
Dl
protect both the metermovementand the circuitry. This fusestrould
be replaced
with one of the sametype so that the protection feature and accuracy of this
instrumentarenot affected.
Accuracy of theRX0.l rangewill bemostaffected
by
usinganincorrect fuse
type.
t6

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NOIJdIUJSIIO IINJUIJ

meter. Any DC voltage which would normally be applied to the gate of Q4B is
slrorted
out in theAC volts functions by the switch.
When measuring
current, a standardresistor
is selected by the RANGE switch
andput in serieswith the circuit to bemeasured.
Thevoltage
(AC or DC) develdped
acrossthe standardresistoris then measured
andreadascurrent on the meter.The
fuse Fl protects low valueresistors
which aremore susceptible
to burnout. Fuse
protection is not requiredon high resistance
value,resistors.
The meter movement
itself is protected on all ranges
because
it isisolatedthru the impedanceconverter.
18