Crown Com-Tech CT-1600 User manual

Com-Tech 1600 Amplifier Service Manual
1
COM-TECH®1600
POWER AMPLIFIER
SERVICE MANUAL
K-SVCCT1600
1-96
Com-Tech®,ODEP® andCrown®are registered trademarks of Crown International, Inc.
MailingAddress:
P.O. Box 1000
Elkhart,INU.S.A. 46515-1000
ShippingAddress:
57620C.R.105
Elkhart, IN U.S.A. 46517
©1996 by CROWN INTERNATIONAL, INC.
Model CT1600B

Com-Tech 1600 Amplifier Service Manual
2
À PRÉVENIR LE CHOC
ÉLECTRIQUE N’ENLEVEZ
PAS LES COUVERTURES.
RIEN DES PARTIES
UTILES À L’INTÉRIEUR.
DÉBRANCHER LA BORNE
AVANT D’OUVRIR LA
MODULE EN ARRIÈRE.
TO PREVENT ELECTRIC SHOCK DO
NOT REMOVE TOP OR BOTTOM
COVERS. NO USER SERVICEABLE
PARTS INSIDE. REFER SERVICING
TO QUALIFIED SERVICE
PERSONNEL. DISCONNECT
POWER CORD BEFORE REMOVING
REAR INPUT MODULE TO ACCESS
GAIN SWITCH.
CAUTION AVIS
WARNING
TO REDUCE THE RISK OF ELECTRIC
SHOCK, DO NOT EXPOSE THIS
EQUIPMENT TO RAIN OR MOISTURE!
The information furnished in this manual does not include all of the details of design, production, or variations
of the equipment. Nor does it cover every possible situation which may arise during installation, operation or
maintenance. If you need special assistance beyond the scope of this manual, please contact the Crown
Technical Support Group.
Mail: P.O. Box 1000 Elkhart IN 46515-1000
Shipping: 57620 C.R. 105 Elkhart IN 46517
Phone: [phone]
FAX: [phone]

Com-Tech 1600 Amplifier Service Manual
3
Table of Contents
Introduction ............................................................ 4
Parts Information .................................................... 5
Specifications......................................................... 6
Theory .................................................................... 7
Electrical Checkout Procedures........................... 12
Parts List (Non Module) ....................................... 16
Module and Schematic Information ..................... 19
Q42828-6 Control Module Parts List .................... 20
Q43213-0 Control Module Parts List .................... 21
Q43241-1 Control Module Parts List .................... 22
Q42706-4 Display Module Parts List.................... 23
Q42758-5 Output Module Parts List .................... 24
Q42889-8 Output Module Parts List .................... 25
Q42973-0 Output Module Parts List .................... 26
Q43051-4 Output Module Parts List .................... 27
Q43192-6 Output Module Parts List .................... 28
Q42782-5 Main Module Parts List........................ 29
Q42919-3 Main Module Parts List........................ 32
Q43010-0 Main Module Parts List........................ 35
Q43041-5 Main Module Parts List........................ 38
Q43131-4 Main Module Parts List........................ 41
Q43240-3 Main Module Parts List........................ 44

Com-Tech 1600 Amplifier Service Manual
4
Crown
Technical Support Group
Factory Service
Parts Department
Mailing Address:
PO Box 1000
Elkhart, IN USA 46515-1000
Shipping Address:
57620 C.R. 105
Elkhart, IN USA 46517
Phone: [phone]
Toll Free: [phone]
FAX: [phone]
This manual contains service information on Crown
poweramplifiers. Itisdesignedtobeusedinconjunc-
tion with the applicable Owner's Manual. However,
some important information is duplicated in this Ser-
viceManualincasetheOwner'sManualisnotreadily
available.
NOTE: THE INFORMATION IN THIS MANUAL IS INTENDED
FOR USE BY AN EXPERIENCED TECHNICIAN ONLY!
Scope
ThisServiceManualinintendedtoapplytoallversions
of the CT-1600B amplifier including the Amcron ver-
sion. The Parts Listings include parts specific for the
USversionandtheEuropeanversion(CT-1600BE13).
For parts specific only to other versions contact the
Crown Technical Support Group for help in finding
part numbers.
ThisService Manual includes several sections. These
sections include Parts Information, Specifications,
Voltage Conversion, Circuit Theory, Electrical Test
Procedures, Non-Module Parts Lists, and Module
Parts Lists. Schematics are attached. Note that com-
ponent parts with circuit board comprise a complete
module. Module part numbers are always associated
withaspecificcircuitboard,althoughanunpopulated
circuit board may be built up with different parts to
create different modules. Note that Crown does not
sell blank (unpopulated) circuit boards.
Each of the compact audio power amplifiers are
designed for professional or commercial use. Provid-
inghighpoweramplificationfrom20Hz to 20KHz with
minimumdistortion, they feature balancedinputs with
bridged and parallel monophonic capability. Specific
features vary depending on model family.
Warranty
Each Owner's Manual contains basic policies as re-
lated to the customer. In addition it should be stated
that this service documentation is meant to be used
only by properly trained service personnel. Because
most Crown products carry a 3 Year Full Warranty
(includingroundtripshippingwithintheUnitedStates),
all warranty service should be referred to the Crown
Factory or Authorized Warranty Service Center. See
theapplicableOwner’sManualforwarrantydetails.To
find the location of the nearest Authorized Service
Centeror obtain instructions for receiving Crown Fac-
toryServicepleasecontacttheCrownTechnicalSup-
port Group (within North America) or your Crown/
Amcron Importer (outside North America).
Introduction

Com-Tech 1600 Amplifier Service Manual
5
Parts Information
shipmentonaC.O.D.orpre-payment(checkorcredit
card) basis.
Terms
Normal terms are pre-paid. Net-30 Days applies to
onlythosefirmshavingpre-establishedaccountswith
Crown. If pre-paying, the order must be packed and
weighed before a total bill can be established, after
which an amount due will be issued and shipment
made upon receipt of pre-payment. New parts re-
turned for credit are subject to a 10% re-stocking fee,
and authorization from the Crown Parts Department
must be obtained before returning parts for credit.
Crownisnotageneralpartswarehouse.Partssoldby
the Crown Parts Department are solely for servicing
Crown/Amcron products. Part prices and availabil-
ity are subject to change without notice.
General Information
Latersections includeboth mechanicaland electrical
parts lists for this product. The parts listed are current
as of the date printed. Crown reserves the right to
modify and improve its products for the benefit of its
customers.
Part Numbering System
As of the printing of this manual, Crown is using two
numbering systems. The elder system always uses
eight characters. The first character is a letter. Com-
monlettersusedareC, D,H,M,P,andQ.Thesecond
through sixth characters are numbers. The numbers
build sequentially (for each prefix letter) as new parts
are added to our parts inventory system. (In some
cases there will be a space then a four character
numberafter theprefixletter; thespace is considered
a character.) The seventh character is usually a hy-
phen,thoughitmaybealettertoindicatea revisionor
specialnote.Thelastcharacteriscalledacheck-digit,
and is useful to Crown for internal tracking.
Crown is in the process of converting to a new part
number system. Length may vary from eight to twelve
characters. There is still a letter prefix, then five
numbers. These five numbers identify a type of part.
The seventh character is a hyphen. Remaining char-
acters identify the details of the type of part identified
by the first part of the number.
Standard and Special Parts
Many smaller electrical and electronic parts used by
Crown are stocked by and available from electronic
supply houses. However, some electronic parts that
appear to be standard are actually special. A part
ordered from Crown will assure an acceptable re-
placement. Structural items such as modules and
panels are available from Crown only.
Ordering Parts
When ordering parts, be sure to give the product
model, and include a description and part number
(CPN/DPN) from the parts listing. Price quotes are
available on request.
Shipment
Shipment will be normally made by UPS or best other
method unless you specify otherwise. Shipments are
made to and from Elkhart, Indiana USA, only. Estab-
lished accounts with Crown will receive shipment
freightprepaidandwillbebilled.Allotherswillreceive
Crown
Parts Department
Mailing Address:
PO Box 1000
Elkhart, IN USA 46515-1000
Shipping Address:
57620 C.R. 105
Elkhart, IN USA 46517
Phone: [phone]
or: [phone]
Toll Free: [phone]
FAX: [phone]

Com-Tech 1600 Amplifier Service Manual
6
Specifications
Unless noted otherwise, all specifications are based
on driving an 8 ohm load per channel, both channels
driven, the sensitivity switch in the 26dB position, the
AC supply is 120VAC at 60Hz. Crown specifications
areguaranteedthrough the warrantyperiod(normally
3years). Because our testing methods aremorestrin-
gent than our published specifications, every Crown
amplifier will exceed its published specifications.
Power
Power
8 Ohm Stereo—540W/Ch
4 Ohm Stereo—875W/Ch
70-V Line Stereo—890W/Ch
8 Ohm Bridge Mono—1720W
4 Ohm Parallel Mono—1080W
2 Ohm Parallel Mono—1750W
Bridge Mono, 140-V Line—1780W
Parallel Mono, 70-V Line—1765W
Load Impedances: Rated for 16, 8, 4, 2, Ohm, and 70-
Vuse.Safewithalltypesofloads,eventotallyreactive
loads.
AC Mains: 120VAC at 60 Hz with standard three-wire
groundedconnectorforNorthAmericanunits;100VAC,
120VAC, 220VAC, and 240VAC at 50 or 60 Hz units
are available when ordered country specific. Com-
Tech amplifiers are not voltage convertable.
Performance
Frequency Response: ±0.1dB from 20 Hz to 20 kHz at 1
Watt.
Phase Response: ±10° from 10 Hz to 20 kHz at 1 Watt.
Signal to Noise Ratio: A-weighted, better than 105 dB
below full rated output. Better than 100 dB below full
rated output from 20 Hz to 20 kHz.
Total Harmonic Distortion (THD): <0.05% from 20 Hz to
1 kHz, increasing linearly to 0.1% at 20 kHz at 500W.
I.M.Distortion:<0.05% from lessthan 164 milliwatts to
520 W at 26 dB gain.
Slew Rate: >13V per microsecond. (Slew rates are
limited to useful levels for ultrasonic/RF protection.)
Damping Factor: >1000 from 10 Hz to 400 Hz.
DC Offset: <10 millivolts.
Input Impedance: Nominally 20K ohms balanced; 10K
ohms unbalanced.
Output Impedance: <10 milliohms in series with <2
microhenries.
Protection Systems: Output Device Emulation Protec-
tion (ODEP) limits drive in the event of dangerous
dynamicthermalconditionswithoutinterruptingpower.
Currentlimitingforshortedloadprotection.DC/LFand
common mode output current Fault circuitry to mute
audio.Delayof4secondsfromturnonmutesamplifier
to prevent dangerous turn-on transients.
Mechanical
InputConnectors:Balancedthree-terminalbarrierblock
for each channel on standard P.I.P.-BB module (in-
cluded)
Output Connectors: Four-terminal barrier block.
Front Panel Controls: A front panel rocker switch used
to power the amplifier on and off.
Back Panel Controls: A three-position switch which
selects Stereo,Bridge-Mono,orParallel-Monomode.
A rotary potentiometer for each channel used to
controloutputlevel.Atwopositionrecessedswitchfor
each channel selects between 8/4 ohm and 70-V
modes. A push button circuit breaker used to protect
the power supply.
InternalControls:Athree-positionswitchselects0.775V,
1.4V, or 26 dB voltage gain input sensitivity.
Indicators:AmberEnableindicatorshowson/offstatus
of low-voltage power supply. A green indicator for
each channel shows the reserve energy status. If no
reserve energy is available the indicator will dim in
proportion to ODEP limiting. A yellow indicator for
each channel flashes in the event of distortion. And
greenSPI(signalpresenceindicator)indicatorsshow
the presence of output signal.
Construction: Black splatter-coat steel chassis with
specially designed flow-through ventilation system.
Mounting: Standard EIA 310 front-panel rack mount
with supports for supplemental rear corner mounting.
Dimensions: 19 inches wide, 7 inches high, 16 inches
deep behind front mounting surface.
Weight: 57 lbs, 14 oz. (26.3 kg)

Com-Tech 1600 Amplifier Service Manual
7
Theory
Overview
It should be noted that over time Crown makes im-
provementsandchangesto theirproductsforvarious
reasons. This manual is up to date as of the time of
writing. For additional information regarding these
amplifiers, refer to the applicable Technical Notes
provided by Crown for this product.
Thissectionofthemanualexplainsthegeneralopera-
tion of a typical Crown power amplifier. Topics cov-
eredincludeFrontEnd,GroundedBridge,andODEP.
Due to variations in design from vintage to vintage
(andsimilaritieswithotherCrownproducts)thetheory
of operation remains simplified.
Features
Com-Tech amplifiers utilize numerous Crown innova-
tionsincludinggrounded bridge and ODEP technolo-
gies. Cooling techniques make use of the what is
essentially air conditioner technology. Air flows bot-
tomtotop,andfronttoside.Airflowsashortdistance
across a wide heatsink. This type of air flow provides
significantly better cooling than the “wind tunnel”
technology used by many other manufacturers. Out-
put transistors are of the metal can type rather than
plastic case. This allows for a significantly higher
thermal margin for the given voltage and current
ratings. All devices used are tested and graded to
ensure maximum reliability. Another electronic tech-
nique used is negative feedback. Almost all power
amplifiers utilize negative feedback to control gain
and provide stability, but Crown uses multiple nested
feedback loops for maximum stability and greatly
improveddamping.MostCrownamplifiershavedamp-
inginexcessof1000inthebassfrequencyrange.This
feedback, along with our compensation and ultra-low
distortion output topology, make Crown amplifiers
superior.
Features specific to the Com-Tech Series’ include
slew rate limiting, and audio muting for delay or
protective action. This amplifier can operate in either
a Bridged or Parallel Mono mode as well as dual
(stereo). A sensitivity switch allows selection of input
voltage required for rated output. Level controls are
mounted on the rear panel and are of the rotary type.
Front panel indicators let the user know the status of
the low voltage power supply (enable), signal pres-
ence, distortion, and an ODEP indicator for each
channel which shows the reserve energy status. In
general, the packaging of this model is designed for
maximumwatt/price/weight/sizevaluewithuserfriendly
features.
Foradditionaldetailsrefertothespecificationsection,
or to the applicable Owner’s Manual.
Front End Operation
Thefront end iscomprisedof three stages: Balanced
Gain Stage (BGS), Variable Gain Stage (VGS), and
theError Amp. Figure 1shows a simplified diagramof
a typical front end with voltage amplification stages.
Balanced Gain Stage (BGS)
Input to the amplifier is balanced. The shield may be
isolated from chassis ground by an RC network to
interrupt ground loops via the Ground Lift Switch. The
non-inverting (hot) side of the balanced input is fed to
the non-inverting input of the first op-amp stage. The
inverting (negative) side of the balanced input is fed
to the inverting input of the first op-amp stage. A
potentiometerisprovidedforcommonmoderejection
adjustment. Electrically, the BGS is at unity gain.
(From an audio perspective, however, this stage
actually provides +6dB gain if a fully balanced signal
is placed on its input.) The BGS is a non-inverting
stage. It’s output is delivered to the Variable Gain
Stage.
Variable Gain Stage (VGS)
FromtheoutputoftheBGS,thesignalgoestotheVGS
where gain is determined by the position of the Sen-
sitivity Switch, and level is determined by the level
control. VGS is an inverting stage with the input being
fedtoits op-amp stage. Because gain after this stage
is fixed at 26dB (factor of 20), greater amplifier sensi-
tivityisachievedbycontrollingtheratiooffeedbackto
input resistance. The Sensitivity Switch sets the input
impedancetothisstageand varies the gain such that
the overall amplifier gain is 26 dB, or is adjusted
appropriately for 0.775V or 1.4V input to attain rated
output.
Error Amp
The inverted output from the VGS is fed to the non-
invertinginputoftheErrorAmpop-ampstagethrough
anACcoupling capacitorandinput resistor.Amplifier
output is fed back via the negative feedback (NFb)
loop resistor. The ratio of feedback resistor to input
resistor fixes gain from the Error Amp input to the
output of the amplifier at 26 dB. Diodes prevent
overdriving the Error Amp. Because the Error Amp
amplifies the difference between input and output
signals, any difference in the two waveforms will
produceanearopenloopgainconditionwhichinturn
results in high peak output voltage. The output of the

Com-Tech 1600 Amplifier Service Manual
8
Theory
Error Amp, called the Error Signal (ES) drives the
Voltage Translators.
Voltage Amplification
The Voltage Translator stage separates the output of
the Error Amp into balanced positive and negative
drive voltages for the Last Voltage Amplifiers (LVAs),
translatingthesignalfromgroundreferenced±15Vto
±Vccreference.LVAsprovidethemainvoltageampli-
fication and drive the High Side output stages. Gain
from Voltage Translator input to amplifier output is a
factor of 25.2.
Voltage Translators
A voltage divider network splits the Error Signal (ES)
into positive and negative drive signals for the bal-
ancedvoltagetranslatorstage.Theseoffsetreference
voltages drive the input to the Voltage Translator
transistors. A nested NFb loop from the output of the
amplifier mixes with the inverted signal riding on the
offsetreferences.Thisnegativefeedbackfixesgainat
theoffsetreference points (and the output of theError
Amp) at a factor of -25.2 with respect to the amplifier
output. The Voltage Translators are arranged in a
common base configuration for non-inverting voltage
gain with equal gain. They shift the audio from the
±15V reference to VCC reference. Their outputs drive
their respective LVA.
Also tied into the Voltage Translator inputs are ODEP
limiting transistors and control/protection transistors.
The ODEP transistors steal drive as dictated by the
ODEP circuitry (discussed later). The control/protec-
tiontransistorsactasswitchestototallyshuntaudioto
ground during the turn-on delay, or during a DC/LF or
Fault protective action.
Last Voltage Amplifiers (LVAs)
The Voltage Translator stage channels the signal to
the Last Voltage Amplifiers (LVA's) in a balanced
configuration.The+LVAand-LVA,withtheirpush-pull
effect through the Bias Servo, drive the fully comple-
mentary output stage. The LVAs are configured as
common emitter amplifiers. This configuration pro-
videssufficientvoltagegainandinvertstheaudio.The
polarity inversion is necessary to avoid an overall
polarity inversion from input jack to output jack, and it
allows the NFb loop to control Error Amp gain by
feedingbacktoitsnon-inverting input(withitspolarity
opposite to the output of the VGS). With the added
voltage swing provided by the LVAs, the signal then
gains current amplification through the Darlington
emitter-follower output stage.
Grounded Bridge Topology
Figure 2 is a simplified example of the grounded
bridge output topology. It consists of four quadrants
of three deep Darlington (composite) emitter-follower
stages per channel: one NPN and one PNP on the
High Side of the bridge (driving the load), and one
NPN and one PNP on the Low Side of the bridge
(controlling the ground reference for the rails). The
output stages are biased to operate class AB+B for
ultra low distortion in the signal zero-crossing region
and high efficiency.
High Side (HS)
The High Side (HS) of the bridge operates much like
aconventionalbipolar push-pulloutputconfiguration.
+
-+ -+ -
BGS VGS Error
Amp
Audio
Inputs
Voltage Divider
NFb Loop
+
-
ODEP Mute
+15V
-15V
+VCC
-VCC
NPN Outputs (+HS)
PNP Outputs (-HS)
Q100
Q103
Q121
Q122
Q101
Q102
Q105
Q110
Voltage
Translators
LVA's
Figure 1. Typical Amplifier Front End and Voltage Amplification Stages.

Com-Tech 1600 Amplifier Service Manual
9
Astheinput drivevoltage becomesmorepositive,the
HSNPNconductsanddeliverspositive voltage to the
load. Eventually the NPN devices reach full conduc-
tion and +Vcc is across the load. At this time the HS
PNP is biased off. When the drive signal is negative
going,theHSPNPconductstodeliver-Vcctotheload
and the HS NPN stage is off.
The output of the +LVA drives the base of predriver
device. Together, the predriver and driver form the
first two parts of the three-deep Darlington and are
biased class AB. They provide output drive through
the bias resistor, bypassing the output devices, at
levelsbelowabout 100mW. An RLC network between
the predriver and driver provide phase shift compen-
sation and limit driver base current to safe levels.
Output devices are biased class B, just below cutoff.
Atabout100mWoutputtheyswitchontoconducthigh
currenttotheload.Togetherwithpredriveranddriver,
the output device provide an overall class AB+B
output.
The negative half of the HS is almost identical to the
positive half, except that the devices are PNP. One
difference is that the PNP bias resistor is slightly
greaterin value sothatPNP output devices runcloser
to the cutoff level under static (no signal) conditions.
This is because PNP devices require greater drive
current.
Theory
+
-
+Vcc (Positive Rail)
-Vcc (Negative Rail)
Load
(speaker)
Input
signal
HIGH SIDE LOW SIDE
Inverting Op-amp
Figure 2. Crown Patented Grounded Bridge Topology
HS bias is regulated by Q18, the Bias Servo. Q18 is a
Vbe multiplier which maintains approximately 3.3V
Vceunderstaticconditions.Thepositiveandnegative
halves of the HS output are in parallel with this 3.3V.
With a full base-emitter on voltage drop across
predrivers and drivers, the balance of voltage results
inapproximately.35Vdropacrossthebiasresistorsin
thepositivehalf,andabout.5Vacrossthebiasresistor
inthenegativehalf.Q18conduction(andthusbias)is
adjustable.
A diode string prevents excessive charge build up
within the high conduction output devices when off.
Flyback diodes shunt back-EMF pulses from reactive
loads to the power supply to protect output devices
from dangerous reverse voltage levels. An output
terminating circuit blocks RF on output lines from
entering the amplifier through its output connectors.
Low Side (LS)
The Low Side (LS) operates quite differently. The
power supply bridge rectifier is not ground refer-
enced, nor is the secondary of the main transformer.
In other words, the high voltage power supply floats
withrespecttoground,but±Vccremainconstantwith
respectto eachother. Thisallows thepower supplyto
deliver +Vcc and -Vcc from the same bridge rectifier
and filter as a total difference in potential, regardless
of their voltages with respect to ground. The LS uses

Com-Tech 1600 Amplifier Service Manual
10
inverted feedback from the HS output to control the
ground reference for the rails (±Vcc). Both LS quad-
rantsarearranged ina three-deepDarlingtonandare
biased AB+B in the same manner as the HS.
Whentheamplifieroutputswingspositive,theaudiois
fed to an op-amp stage where it is inverted. This
invertedsignal isdelivered directlyto thebasesofthe
positive(NPN) andnegative (PNP) LSpredrivers. The
negative drive forces the LS PNP devices on (NPN
off). As the PNP devices conduct, Vce of the PNP
Darlington drops. With LS device emitters tied to
ground, -Vcc is pulled toward ground reference.
Sincethepowersupplyisnotgroundreferenced(and
the total voltage from +Vcc to -Vcc is constant) +Vcc
is forced higher above ground potential. This contin-
ues until, at the positive amplifier output peak, -Vcc =
0V and +Vcc equals the total power supply potential
with a positive polarity. If, for example, the power
supplyproducedatotalof70Vfromrailtorail(±35VDC
measured from ground with no signal), the amplifier
output would reach a positive peak of +70V.
Conversely, during a negative swing of the HS output
where HS PNP devices conduct, the op-amp would
output a positive voltage forcing LS NPN devices to
conduct. This would result in +Vcc swinging toward
ground potential and -Vcc further from ground poten-
tial. At the negative amplifier output peak, +Vcc = 0V
and -Vcc equals the total power supply potential with
anegativepolarity.Usingthesameexampleasabove,
a 70V supply would allow a negative output peak of -
70V. In summary, a power supply which produces a
total of 70VDC rail to rail (or ±35VDC statically) is
capableofproducing140Vpeak-to-peakattheampli-
fier output when the grounded bridge topology is
used. The voltage used in this example are relatively
close to the voltages of the PB-1/460CSL.
The total effect is to deliver a peak to peak voltage to
the speaker load which is twice the voltage produced
bythepowersupply.Benefitsinclude full utilization of
the power supply (it conducts current during both
halves of the output signal; conventional designs
require two power supplies per channel, one positive
and one negative), and never exposing any output
device to more than half of the peak to peak output
voltage (which does occur in conventional designs).
Low side bias is established by a diode string which
also shunts built up charges on the output devices.
Bias is adjustable via potentiometer. Flyback diodes
Theory
perform the same function as the HS flybacks. The
output of the LS is tied directly to chassis ground via
ground strap.
Output Device Emulation Protection (ODEP)
Tofurtherprotecttheoutputstages,aspeciallydevel-
oped ODEP circuit is used. It produces a complex
analog output signal. This signal is proportional to the
always changing safe-operating-area margin of the
output transistors. The ODEP signal controls the Volt-
age Translator stage by removing drive that may
exceed the safe-operating-area of the output stage.
ODEP senses output current by measuring the volt-
age dropped across LS emitter resistors. LS NPN
current (negative amplifier output) and +Vcc are
sensed,thenmultiplied toobtaina signalproportional
tooutputpower.PositiveandnegativeODEPvoltages
areadjustableviatwopotentiometers.Across±ODEP
are a PTC and a thermal sense (current source). The
PTC is essentially a cutoff switch that causes hard
ODEP limiting if heatsink temperature exceeds a safe
maximum, regardless of signal level. The thermal
sense causes the differential between +ODEP and –
ODEPtodecreaseasheatsinktemperatureincreases.
Anincreaseinpositiveoutputsignaloutputintoaload
will result in –ODEP voltage dropping; an increase in
negativeoutputvoltageandcurrentwillcause+ODEP
voltage to drop. A complex RC network between the
±ODEP circuitry is used to simulate the thermal barri-
ers between the interior of the output device die
(immeasurable by normal means) and the time delay
fromheatgenerationat the die until heat dissipates to
the thermal sensor. The combined effects of thermal
history and instantaneous dynamic power level result
in an accurate simulation of the actual thermal condi-
tion of the output transistors.

Com-Tech 1600 Amplifier Service Manual
11
Theory
NEGATIVE
LOW SIDE
OUTPUT
PNP STAGE
POSITIVE
LOW SIDE
OUTPUT
NPN STAGE
NEGATIVE
HIGH SIDE
OUTPUT
PNP STAGE
POSITIVE
HIGH SIDE
OUTPUT
NPN STAGE
HIGH SIDE
BIAS
SERVO
+LVA
-1
-LVA
-1
+VOLTAGE
TRANSLATOR
-VOLTAGE
TRANSLATOR
OUTPUT
DEVICE
EMULATION
PROTECTION
ERROR
AMP
VGSBGS
BALANCED
INPUTS
INVERTING
BRIDGE
BALANCE
LOW SIDE
BIAS
DIODE
STRING
-1
-1
MAIN NEGATIVE FEEDBACK (NFb) LOOP
Figure 3. Typical Crown Amplifier Basic Block Diagram (One Channel Shown)

Com-Tech 1600 Amplifier Service Manual
12
Electrical Checkout Procedures
General Information
The following test procedures are to be used to verify
operation of this amplifier. DO NOT connect a load or
inject a signal unless directed to do so by the proce-
dure. These tests, though meant for verification and
alignment of the amplifier, may also be very helpful in
troubleshooting. For best results, tests should be
performed in order.
AlltestsassumethatACpowerisfromaregulated120
VAC source. Test equipment includes an oscillo-
scope, a DMM, a signal generator, loads, and I.M.D.
and T.H.D. noise test equipment.
Standard Initial Conditions
Level controls fully clockwise.
Stereo/Mono switch in Stereo.
Sensitivity switch in 26 dB fixed gain position.
70-V mode switches in the 8/4 ohm position.
It is assumed, in each step, that conditions of the
amplifier are per these initial conditions unless other-
wise specified.
Test 1: DC Offset
Spec: 0 VDC, ±10 mV.
InitialConditions:Controlsperstandard,inputsshorted.
Procedure: Measure DC voltage at the output connec-
tors (rear panel). There is no adjustment for output
offset.Ifspecisnotmet,thereisanelectricalmalfunc-
tion. Slightly out of spec measurement is usually due
to U104/U204 out of tolorance.
Test 2: Output Bias Adjustment
Spec: 300 to 320 mVDC.
InitialConditions: Controlsperstandard, heatsinktem-
perature less than 40°C.
Procedure: Measure DC voltage on the output module
across R02 (5.6 ohm), adjust R26 if necessary. Mea-
sureDCvoltageontheoutputmoduleacrossR21(5.6
ohm), adjust R23 if necessary. Repeat for second
channel.
Test 3: ODEP Voltage Adjustment
Spec: Bias Per Chart, ±0.1V DC.
Initial Conditions: Controls per standard, heatsink at
room temperature 20 to 30°C (68 to 86°F). Note: This
adjustment should normally be performed within 2
minutes of turn on from ambient (cold) conditions. If
possible measure heatsink temperature, if not mea-
sure ambient room temperature. Use this information
when referencing the following chart.
The following list of ODEP bias voltages VS. tempera-
ture is based on the use of Main Modules built on any
circuit board up to and including the D 7993-5 board.
°F °C V–ODEP V+ODEP
66 18.9 –10.31 11.41
68 20.0 –10.26 11.36
70 21.1 –10.20 11.30
72 22.2 –10.14 11.24
74 23.3 –10.09 11.19
76 24.4 –10.03 11.13
77 25.0 –10.00 11.10
78 25.6 –9.97 11.07
80 26.7 –9.91 11.01
82 27.8 –9.86 10.96
84 28.9 –9.80 10.90
86 30.0 –9.74 10.84
88 31.1 –9.69 10.79
90 32.2 –9.63 10.73
92 33.3 –9.57 10.67
94 34.4 –9.51 10.61
The following list of ODEP bias voltages VS. tempera-
ture is based on the use of Main Modules built on any
circuit board after the D 7993-5 board.
°F °C V–ODEP V+ODEP
66 18.9 –10.31 10.31
68 20.0 –10.26 10.26
70 21.1 –10.20 10.20
72 22.2 –10.14 10.14
74 23.3 –10.09 10.09
76 24.4 –10.03 10.03
77 25.0 –10.00 10.00
78 25.6 –9.97 9.97
80 26.7 –9.91 9.91
82 27.8 –9.86 9.86
84 28.9 –9.80 9.80
86 30.0 –9.74 9.74
88 31.1 –9.69 9.69
90 32.2 –9.63 9.63
92 33.3 –9.57 9.57
94 34.4 –9.51 9.51
–ODEPProcedure: Measurepin3 ofJ500 and,ifneces-
sary, adjust R121 to obtain V–ODEP as specified above.
Measure pin 3 of J500 and, if necessary, adjust R221
to obtain V–ODEP as specified above.
+ODEPProcedure: Measurepin4 ofJ500 and,ifneces-
sary, adjust R132 to obtain V+ODEP as specified above.
Measure pin 4 of J500 and, if necessary, adjust R232
to obtain V+ODEP as specified above.

Com-Tech 1600 Amplifier Service Manual
13
Test 4: AC Power Draw
Spec: 80 Watts maximum quiescent.
Initial Conditions: Controls per standard.
Procedure: With no input signal and no load, measure
AC line wattage draw. If current draw is excessive,
check for high AC line voltage or high bias voltage.
Test 5: Common Mode Rejection
Spec at 100 Hz: –70 dB.
Spec at 20 kHz: –50 dB.
Initial Conditions: Controls per standard.
Procedure: Noload. Inject a0dBu (.775VRMS) 100Hz
sine wave into each channel, one channel at a time,
with inverting and non-inverting inputs shorted to-
gether. At the output measure less than –44 dBu
(4.9mVRMS). Inject a 0 dBu 20 kHz sine wave into
eachchannel,onechannelatatime,withinvertingand
non-inverting inputs shorted together. At the output
measure less than –24 dBu (49mVRMS). For Main
Modules with board numbers lower than D 7993-5
adjust N100 and N200 to calibrate CMR. For Main
Modules with board number D 7993-5 or greater
adjust R921 and R1021.
Test 6: Voltage Gain
Spec 26dB Gain: Gain of 20.0 ±3%.
Spec 0.775V 8/4 ohm Sensitivity: ±6%.
Spec 0.775V 70-V Sensitivity: ±6%.
Initial Conditions: Controls per standard.
Procedure: No load connected. Inject a 0.775 VAC 1
kHz sine wave with the Sensitivity Switch in the 26 dB
position.Measure15.5VAC ±0.5 VAC at the amplifier
output. Inject a 0.775 VAC 1 kHz sine wave with the
Sensitivity Switch in the 0.775V 8/4 ohm position.
Measure 65.7 VAC ±3.9 VAC at the amplifier output.
Injecta0.775VAC1kHzsinewavewiththeSensitivity
Switch in the 0.775 VAC 70-V position and the Output
Mode Switch in the 70-V position. Measure 70.7 VAC
±4.2VACattheamplifieroutput.ReturntheSensitivity
Switch to the 26 dB position. Return the Output Mode
Switches to the 8/4 ohm position.
Test 7: Phase Response
Spec: ±10° from 10 Hz to 20 kHz at 1 Watt.
InitialConditions:Controlsperstandard,8ohmloadon
each channel.
Procedure: Inject a 1 kHz sine wave and adjust for 1
wattoutput(2.8 VAC).Check inputandoutputsignals
against each other, input and output signals must be
within 10° of each other.
Electrical Checkout Procedures
Test 8: Level Controls
Spec: Level controlled by level controls.
Initial Conditions: Controls per standard.
Procedure:Noload.Injecta1kHzsinewave.Withlevel
controls fully clockwise you should see full gain. As
controls are rotated counterclockwise, observe simi-
lar gain reduction in each channel. When complete,
return level controls to fully clockwise position.
Test 9: Current Limit
Spec: Current Limit at 39 Amps, ±6 Amps.
Initial Conditions: Controls per standard.
Procedure:Load eachchannel to1ohm. Injecta 1kHz
differentiated (or 10% duty cycle) square wave. See
figure 4. Increase output level until current limit oc-
curs. Current limit should occur at 39 ±6 Amps (39
Vpk).Observeclean(nooscillations)currentclipping.
Test 10: Slew Rate & 10 KHz Square Wave
Spec: 17 - 25 V/µS, 8 ohm load.
Initial Conditions: Controls per standard.
Procedure: Load each channel to 8 ohms. Inject a 10
kHz square wave to obtain 35 Volts zero-to-peak at
eachoutput.Observe the slope of the square wave. It
shouldtypicallymeasure17-25V/µS.Also,thesquare
wave must not include overshoot, ringing, or any type
of oscillation.
Test 11: Crosstalk
Spec: -60 dB at 20 kHz.
Initial Conditions: Controls per standard. Terminate
input of channel not driven with 600 ohms.
Procedure:8ohmloadoneachchannel.Injecta20kHz
sinewaveintothechannel1inputandincreaseoutput
level to 64 VAC. Measure less than 64 mVAC at the
output of channel 2. Inject a 20 kHz sine wave into the
channel 2 input and increase output level to 64 VAC.
Measure less than 64 mVAC at the output of Ch 1.
In Out
.047 uF
1K Ohm
Figure 4. Differentiator Circuit

Com-Tech 1600 Amplifier Service Manual
14
Electrical Checkout Procedures
Test 12: Output Power
Spec at 8 Ohm Stereo: ≥540 Watts/Ch at 0.1% THD
Spec at 4 Ohm Stereo: ≥850 Watts/Ch at 0.1% THD
Specat70-VMode,Stereo: ≥875Watts/Chat0.1%THD
Initial Conditions: Controls per standard
Procedure:Loadeachchannelto8ohms.Injecta1kHz
sine wave and measure at least 65.72 VAC at the
outputofeachchannel.Loadeachchannelto4ohms.
Inject a 1 kHz sine wave and measure at least 58.31
VAC at the output of each channel. Switch each
channeltothe70-Vmode. Load each channel to 6.25
ohms. Inject a 1 kHz sine wave and measure at least
70.7 VAC at the output of each channel. All power
measurements must be at less than 0.1% THD.
Test 13: Reactive Loads
Spec: No oscillations. Safe with all types of loads.
Initial Conditions: Controls per standard.
Procedure Capacitive: Load each channel to 8 ohms in
parallelwith.94µF.Injecta20kHzsinewavewith56.9
VAC output for 10 seconds.
Procedure Inductive: Load each channel to 8 ohms in
parallel with 159µH. Inject a 1 kHz sine wave with 15
VAC output for 10 seconds.
Procedure Torture: Loadeachchannel withtheprimary
(red and black leads) of a PS-U transformer (CPN D
7040-5).Eachchannelinthe70-Vmode.Injecta10Hz
sine wave with an output level sufficient enough to
cause 3 to 5 flyback pulses for 10 seconds.
ProcedureShort: Inject a60Hz sine wave into the input
andadjust for 5 VACatthe output. Short eachchanel,
one at a time, for 10 seconds.
Test 14: ODEP Limiting
Spec:NooscillationonODEPlimitingwaveform;either
channel controls limiting in Parallel Mono mode.
Initial Conditions: Controls per standard; rag or other
obstruction blocking fan blade so it does not turn.
Procedure: Load the amplifier to 2 ohms per channel.
Injecta 60 Hz sine wave intoeachchannel and adjust
the output to 15 VAC. Allow the amplifier to heat up
untilyouobserve awave formsimilar tofigure5.Allow
the amplifier to cool for a few miniutes. Switch the
amplifier to Parallel Mono mode and remove the load
from channel 2. Inject a 60 Hz sine wave into each
channel and adjust the output to 15 VAC. Allow the
amplifier to heat up and observe limiting on both
channels.
Test 15: LF Protection
Spec: Amplifier mutes for dangerous subsonic fre-
quencies.
Initial Conditions: Controls per standard.
Procedure: No load. Inject a .5 Hz 6 Vp-p, or a 2 Hz 6
VACsine wave into eachchanneland verify that each
channel cycles into mute.
Test 16: Signal to Noise Ratio
Spec:≥100dBbelow8ohmratedcontinuousaverage
20-20kHz power.
Initial Conditions: Controls per standard. Short inputs.
Procedure: Load each channel to 8 ohms. Measure
less than 648µV at the output of each channel (20 Hz-
20 kHz bandpass filter).
Test 17: Turn off Transients
Spec: < 80mV across an 8 ohm speaker load
Initial Conditions: Controls per standard.
Procedure: Load the output with an 8 ohm speaker.
Fromanoncondition,turnofftheamplifierandmonitor
the output noise at the time of turn off.
Note: Turn off noise may increase significantly if the
amplifier is cycled off and on.
Figure 5. ODEP Limiting Wave Form

Com-Tech 1600 Amplifier Service Manual
15
Electrical Checkout Procedures
Test 18: Intermodulation Distortion
Spec at 0 dB output: ≤0.01%.
Spec at -35 dB output: ≤0.05%.
Initial Conditions: Controls per standard.
Procedure: Load each channel to 8 ohms. Inject a
SMPTEstandardIMsignal(60Hzand7kHzsinewave
mixed at 4:1 ratio). Set the 60 Hz portion of the sine
wave to 51 volts RMS. Set the 7 kHz portion to 25%.
With an IM analyzer measure less than 0.01% IMD.
Repeat test at -35 dB (reference 51 volts RMS, 60 Hz
portion) and measure less than 0.05% IMD.
Test 19: Clipping
Spec: No protective action during test.
Initial Conditions: Controls per standard.
Procedure:Loadeachchannelto8ohms.Injecta1kHz
sine wave into each input and drive the output 6 dB
into clip for 10 seconds. The amplifier should not
activate any protective circuits (ODEP, Fault, or LF
Protection).
Post Testing
After completion of testing, if all tests are satisfactory,
the amplifier controls should be returned to the posi-
tionsrequiredbycustomer. Ifconditionsare unknown
or unspecified, factory settings are as follows:
Level Controls: 9 to 11 O'Clock.
Sensitivity Switch: 0.775V 8/4 Ohm.
Stereo/Mono Switch: Stereo.
70-V Mode Switches: 8/4 Ohm position.
Power: Off

Com-Tech 1600 Amplifier Service Manual
16
Supplimental Items
CPN Item Quantity
A10087-71012 Rack Screw, 10-32 x .75 8
C 3342-0 Feet, Selfstick Black 4
D 4137-2 Nylon Washer 4
A10086-70808 Screw, 8-32 x .5 (For volume cover) 2
A10101-12 Spacer, #8 x 5/16OD x 1/4L (For volume cover) 2
F11489-6 Plexiglass Plate (Volume cover) 1
K80636-2 CT Series Reference Manual 1
Power Supply
CPN Item Quantity
A10086-70604 Screw, 6-32 x .25 2
A10098-7 #6 Belleville Spring Washer 2
C 7786-4 Screw, 10-32 x 5.0 (For transformer) 2
C 7859-9 Relay, 30A 120VAC SPST (100V-120V Models) 1
C 9837-3 Breaker, 30 Amp (100V-120V Models) 1
C10177-1 Breaker, 20 Amp VDE (200V-240V Models) 1
C 9924-9 Faston, TAB .250 Stud Mount 2
D 7145-2 Power Transformer (120V 60 Hz) 1
D 9008-0 Power Transformer (220V/240V) 1
D 8087-5 Power Transformer (100V/120V) 1
A10094-8 Washer, #10 Internal Tooth 4
A10098-5 Washer, 1/4" Belleville Spring 4
C 8752-5 Bridge Rectifier, 35A 400V 2
C 9852-2 Capacitor, 6300µF 200V Electrolytic 2
C 9870-4 Screw, 10-32 x .38 4
D 2934-4 Solder Lug, .218 Hole 4
D 6764-1 Washer, Shoulder 4
D 8438-0 Bracket, Capacitor 2
Output Assembly (One Per Channel)
CPN Item Quantity (Per Channel)
A10315-1 Screw, 6-32 x .56 Hex Washer Head 12
C 9387-9 Plasti-Rivit, .156 2 Prong Blk 2
C 9491-9 Screw, 6-32 x .312 Pan Hd 29
C 8188-2 Output Power Transistor, PNP 6
C 8187-4 Output Power Transistor, NPN 6
C 8573-5 Driver Transistor, 2SA1186 PNP 2
C 8574-3 Driver Transistor, 2SC2837 NPN 2
M20591-0 Old Style Driver Transistor Assm. NPN, 2SC2527 2
M20590-2 Old Style Driver Transistor Assm. PNP, 2SA1077 2
D 7665-9 Mounting Clip, TO3P (For Drivers) 2
D 7666-7 Mounting Bracket, TO3P (For Drivers) 2
D 7796-2 Sil Pad, 2.87 x 14.57 (Between Heatsink & Chassis) 1
D 6280-8 Sil Pad for use with Output Board P10315-3 1
D 6104-0 Sil Pad for use with Output Board P10233-8 1
D 7797-0 Output Pad (Between Module and Chassis) 1
C 7597-4 Output Pad for use with Output Board P10315-3 1
D 7026-4 Output Pad for use with Output Board P10233-8 1
D 8774-8 PTC, 95DegC Cast Alum. 1
F12019-0 Heatsink (Under Diode String) 1
Parts List (Non-Module)

Com-Tech 1600 Amplifier Service Manual
17
Parts List (Non-Module)
Output Assembly Cont. (One Per Channel)
C 8813-5 Bias Transistor MPS8097/MPSA18 NPN (Q18) 1
B 5842-8 Tubing, #24 Thin Wall Red (For Q18) Order in Inches
C 5826-0 LM234Z-6 Thermal Sense (S100/200) 1
B 5464-1 Tubing, #24 Teflon Thin Wall Order in Inches
D 8197-2 Shroud, 1.75 x 14.45 Paper 1
M21324-5 Aluminum Heat Sink, 3/4" With Fins 2
Back Panel Assembly
CPN Item Quantity
D 8367-1 Knob, .5 Dia. Level Control 2
A10086-10410 Screw, 4-40 x .62 2
A10086-70808 Screw, 8-32 x .5 4
A10094-2 Lockwasher, #4 Internal Star 2
A10100-7 Aluminum Spacer, .250OD x .140ID x .312L 2
A10109-70808 Screw, 8-18 x .5 4
A10214-7 Strain Relief 1
C10187-0 Strain Relief (For European Power Cord) 1
A11793-0101D Power Cord, 14-3 SJT Neon UL/CSA 1
A10793-0503D Power Cord, European Plug (E-13 Amplifiers) 1
C 4508-5 IC Socket, 16 Pin 1
C 5990-4 Barrier Block, 4 Term. 1
C 6821-0 Edge Card Connector, 22 Contact 1
C 7957-1 Slide Switch, DPDT 15A (70-V Mode) 2
C 8812-7 Cable Tie, 5.5" 2
C10060-9 Header, 5 Pin R Angle Locking 1
D 6899-5 Ribbon Connector, PIP Daisy 1
D 7623-8 Cable, 10" 22AWG With Terminals 1
F12725-2 Back Panel 1
P10286-6 PIP Interconnect Board 1
Chassis Front Assembly
CPN Item Quantity
A10031-1 Captive Nut, 8-32 x .060 Flush (For rack ears) 4
A10110-70812 Screw, 8-32 x .75 PH Head (For Grille) 5
A10101-5 Nylon Washer, .5 x .136 x .02 (For Grille) 5
A10173-1 Clip, Filter Grille 5
C 5297-4 Screw, 8-32 x .37 (For rack ears) 4
C 6487-0 Power Switch, 2 Pole 22 Amp Rocker 1
D 7119-7 Air Filter, 4.9 x 16.23 1
F11574J4 Front Panel Overlay 1
F12708-8 End Cap (For Rack ears) 2
F12712-0 Grille, Filter 1
F11577J7 4.024" Finger Guard 1
Main Chassis Assembly
CPN Item Quantity
A10094-3 Washer, #6 Internal Star, Black 11
A10094-4 Washer, #6 Internal Star, Zinc 2
A10101-13 Washer, .25OD X .175ID X .187L Fiber Spacer 5
A10101-14 Washer, .380OD x .170ID x .125 5
A10110-70605 Screw, 6-32 x .312 Taptite (For covers) 9

Com-Tech 1600 Amplifier Service Manual
18
Parts List (Non-Module)
Main Chassis Assembly Cont.
CPN Item Quantity
D 7249-2 Label, 3 Position Voltage Gain 1
D 8501-5 Cover 2
A10086-10606 Screw, 6-32 x .375 2
A10086-70806 Screw, 8-32 x .37 1
A10094-6 Washer, #8 Internal Star 2
A10099-7 Shoulder Washer, #10 Nylon 4
A10109-10822 Screw, 8-18 x 1.375 2
A10110-70812 8-32 x .750 Taptite 2
A10102-5 Hex Nut, 6-32 2
A10106-70806 Screw, #8 x .37 Hex Washer Head 4
A10192-1 Snap Bushing, OCB .500 4
C 6066-2 Resistor, 33 Ohm 10W 1
C 7858-1 Fan, 4.7" Ball Bearing 1
C 1811-6 4" Cable Tie 8
C 3163-0 Solder Lug, #6 1
C 6457-3 Screw, #8 x 3/8 2
C 6873-1 .875 Spacer Toggle Nut Plastic 2
C 7862-3 Board Support, 7/8 Locking 2
C 9491-9 Screw, 6-32 x .312 5
C10111-0 Button, Mtg. 2
D 6109-9 .25 Tab #8H Terminal Strip 1
D 7060-3 Sil Pad, 7 Mil 2.05 x .775 1
F11632-1 Bracket, Transformer Mtg. 1
F12643-7 Chassis, 7" 1
PIP-BB
CPN Item Quantity
M46011-9 PIP-BB Assembly 1
A10086-70806 Screw, 8-32 x .37 2
A10094-5 Lockwasher, #8 Internal Star Black 2
A10110-10608 Screw, 6-32 x .5 4
A10266-2202 Resistor, 22 Ohm .5W 2
C 3842-9 Barrier Block, 3 Position 2
C 6806-1 Capacitor, .01µF 100V 2
C 7161-0 Screw, #8 x 1/4 #6 PNHD 2
F12553J7 Panel 1
P10343-5 PC Board 1

Com-Tech 1600 Amplifier Service Manual
19
Module and Schematic Information
Module History
The Com Tech 1600B amplifier was introduced in
1990. Since then there have been several updates
and revisions, some of which called for new modules.
The following is a list of all modules used up to this
date, January 1996.
Output Modules: (left and right are identical)
Q42758-5
Original Output Module on P10233-8 or P10265-5
board.
Q42889-8
Output Module on P10315-3 board.
Q42973-0
Output Module on P10337-7 board. No longer avail-
able. Use Q43192-6 as service replacement.
Q43051-4
Output Module on P10337-7 board. No longer avail-
able. Use Q43192-6 as service replacement.
Q43192-6
Output Module on P10396-3 board.
Main Modules:
Q42782-5
Original B Version Main Module on D 7222-9 board.
No longer available. Use Q43131-4 as a service
replacement.
Q42919-3
MainModule on D7605-5board. No longeravailable.
Use Q23131-4 as a service replacement.
Q43010-0
Main Module on D 7911-7 board. Use Q43131-4 as a
service replacement.
Q43041-5
MainModule on D7993-5board. No longeravailable.
Use Q43131-4 as service replacement.
Q43131-4
Main Module on D 8283-0 board.
Q43240-3
Main Module on D 8369-7 board. Detent Pots. Not
reverse compatible.
Control Module:
Q42828-6
CT-1600 Control Module on P10251-0 board. No
longer available. Use Q43241-1 as service replace-
ment.
Q43213-0
CT-1600 Control Module on P10404-5 board. No
longer available. Use Q43241-1 as service replace-
ment.
Q43241-1
CT-1600 Control Module on P10405-2 board.
Display Module:
Q42706-4
CT display on D 7083-5 board.
Schematic Information:
The schematics provided are representative only.
There may be slight variations between amplifier to
amplifier. These schematics are intended to be used
for troubleshooting purposes only.
For amplifiers with main boards D 7605-5 or earlier,
refer to schematic number J0482-0.
For amplifiers with main boards D 7911-7, D 7993-5,
or D 8283-0 refer to schematic number J0525-6.
For amplifiers with main board D 8369-7 refer to
schematic number J0633-8.

Com-Tech 1600 Amplifier Service Manual
20
Q42828-6 Control Module (P10251-0 board) Parts Lists
Capacitors
C700 C800 C 8426-6 .1µF 250V
C701 C801 C 8426-6 .1µF 250V
C900 C 8963-8 .47µF 250V
Diodes
D700 D800 C 3181-2 1N4148
D900 C 2851-1 1N4004
Relays
K1 C 7860-7 SPST
Transistors
Q700 Q800 C 3625-8 PNP 2N4125
Q701 Q801 C 7663-5 Triac MAC224A4
Q900 C 3625-8 PNP 2N4125
Q901 C 3625-8 PNP 2N4125
Q902 C 3625-8 PNP 2N4125
Resistors
R700 R800 A10266-1222 1.2K .5W
R701 R801 A10266-1812 180 .5W
R900 A10266-2722 2.7K .5W
R901 A10266-1021 1.5K .5W
R902 C 7669-2 300 10W
R903 C 7669-2 300 10W
R904 A10266-3902 39 .5W
ICs
U700 U800 C 7664-3 MOC3031 Optotriac
U901 C 7665-0 MOC3011 Optotriac
U902 C 7665-0 MOC3011 Optotriac
Misc.
Board P10251-0
J900 C 7672-6 8 Pin MTA Header
Tab Terminal C 7817-7 W1-W3,W100-W102
W200-W202
0 Ohm Jmp C 5868-2