Mackie HR824 User manual

HR824
High Resolution
Active Studio Monitor
SERVICE MANUAL

1999MACKIEDESIGNS, INC.
820-183-00

Page 3 is interactive

2
CAUTION
AVIS
RISK OF ELECTRIC SHOCK
DO NOT OPEN
RISQUE DE CHOC ELECTRIQUE
NE PAS OUVRIR
CAUTION: TO REDUCE THE RISK OF
ELECTRIC SHOCK DO NOT REMOVE
THE COVER (OR BACK)
NO USER SERVICEABLE PARTS INSIDE
REFER SERVICING TO QUALIFIED
PERSONNEL
WARNING: TO REDUCE THE RISK OF
FIRE OR ELECTRIC SHOCK, DO NOT
EXPOSE THIS PRODUCT TO RAIN OR
MOISTURE
TO PREVENT ELECTRIC SHOCK, DO
NOT USE THIS POLARIZED PLUG WITH
AN EXTENSION CORD, RECEPTACLE OR
OTHER OUTLET UNLESS THE BLADES
CAN BE FULLY INSERTED TO PREVENT
BLADE EXPOSURE.
ATTENTION: POUR EVITER LES
RISQUES DE CHOC ELECTRIQUE, NE
PAS ENLEVER LE COUVERCLE. AUCUN
ENTRETIEN DE PIECES INTERIEURES
PAR L'USAGER. CONFIER L'ENTRETIEN
AU PERSONNEL QUALIFIE.
AVIS:POUR EVITER LES RISQUES
D'INCENDIE OU D'ELECTROCUTION,
N'EXPOSEZ PAS CET ARTICLE A LA
PLUIE OU A L'HUMIDITE.
POUR PREVENIR LES CHOCS
ELECTRIQUES NE PAS UTILISER CETTE
FICHE POLARISEE AVEC UN
PROLONGATEUR, UN PRISE DE
COURANT OU UNE AUTRE SORTIE DE
COURANT, SAUF SI LES LAMES
PEUVENT ETRE INSEREES A FOND
SANS LAISSER AUCUNE PARTIE A
DECOUVERT.
This apparatus does not exceed the Class A/Class B (whichever is applicable) limits for radio
noise emissions from di
g
ital apparatus as set out in the radio interference re
g
ulations of the
Canadian Department of Communications.
ATTENTION :Le présent appareil numérique n'émet pas de bruits radioélectriques dépassant
las limites applicables aux appareils numériques de class A/de class B (selon le cas) prescrites
dans le ré
g
lement sur le brouilla
g
e radioélectrique édicté par les ministere des communications
du Canada.
This equipment has been tested and found to comply with the limits for a Class A di
g
ital
device, pursuant to part 15 of the FCC rules. These limits are desi
g
ned to provide reasonable
protection a
g
ainst harmful interference when the equipment is operated in a commercial
environment. This equipment
g
enerates, uses, and can radiate radio ener
g
y and, if not
installed properly and used in accordance with the instruction manual, may cause harmful
interference to radio communications. Operation of this equipment in a residential area is likely
to cause harmful interference in which case the user will be required to correct the interference
at his own expense.
The lightning flash with arrowhead symbol within an equilateral
triangle is intended to alert the user to the presence of uninsulated
"dangerous voltage" within the product's enclosure, that may be
of sufficient magnitude to constitute a risk of electric shock to persons.
Le symbole éclair avec point de flèche à l'intérieur d'un triangle
équilatéral est utilisé pour alerter l'utilisateur de la présence à
l'intérieur du coffret de "voltage dangereux" non isolé d'ampleur
suffisante pour constituer un risque d'éléctrocution.
The exclamation point within an equilateral triangle is intended to
alert the user of the presence of important operating and maintenance
(servicing) instructions in the literature accompanying the appliance.
Le point d'exclamation à l'intérieur d'un triangle équilatéral est
employé pour alerter les utilisateurs de la présence d'instructions
importantes pour le fonctionnement et l'entretien (service) dans le
livret d'instruction accompagnant l'appareil.

3
CONTENTS
SHIPPING ............................................................................................3
INTRODUCTION .................................................................................4
TECHNICAL SUPPORT ...................................................................4
DISCLAIMER...................................................................................4
OVERVIEW.....................................................................................5
REAR PANEL ..................................................................................6
FRONT PANEL ................................................................................7
SPECIFICATIONS ................................................................................8
BLOCK DIAGRAM .............................................................................9
WIRING DIAGRAM..........................................................................10
PACKAGING PARTS........................................................................11
QUICK PARTS.............................................................................. 11-12
TEST PROCEDURES ..................................................................... 13-19
PARTS LIST ................................................................................... 21-25
IC AND TRANSISTOR CHARTS .................................................. 25-26
FOLD-OUT SECTIONS:
SCHEMATICS.........................................................................A1-A2
PRINTED CIRCUIT BOARDS REV A......................................A3-A4
PRINTED CIRCUIT BOARDS REV B ......................................A5-A6
FINAL ASSEMBLY ............................................................... A7-A13
SHIPPING
When shipping this speaker, make sure that all the original packaging is used, including
both the inner and outer boxes, and especially the thin, white sheet material. If shipped
in just one box or without the sheet material, the lovely finish can be damaged. Shipping
damage due to improper packaging is not covered under Warranty!
If you do not have the original packaging, it can be ordered from our parts department.
Never use loose-fill foam pieces (peanuts) as these can damage the finish and get inside
the amplifier section.
Click on any item to open that page

4
INTRODUCTION
This manual contains service information for the HR824 Powered Studio Monitor. It is
recommended that you also have a copy of the owner’s manual as this contains the
complete operating instructions.
To service the HR824, technicians should be familiar with op-amp based and discrete
amplifier circuitry, speaker repair and speaker performance testing. Presentation of this
manual does not constitute endorsement of qualifications by Mackie Designs.
PROTECT YOUR HEARING
The HR-824 speakers are capable of producing high sound pressure levels. We
recommend the use of hearing protectors to prevent permanent hearing loss.
SERVICE TECHNICAL ASSISTANCE
MackieDesigns, ServiceTechnical Assistance,is available8AM -5PM PST,Monday through
Friday for Authorized Mackie Service Centers, at 1-800-258-6883. Feel free to call with any
questions and speak with a carefully-calibrated technician. If one is not available, leave
a detailed message and a qualified Mackoid will return your call asap.
DISCLAIMER
The information contained in this manual is proprietary to Mackie Designs, Inc. The entire
manual is protected under copyright and may not be reproduced by any means without
express written permission from Mackie Designs Inc.
WARNING
Service on the HR824 must only be
undertakenbyexperienced
service technicians.
!SMD!
The HR824 makes extensive use of
surface mount components.
Service technicians should have the
tools, experience and patience to
perform surface mount rework.

5
THE AMPLIFIERS
• The Fast Recovery amplifier design uses low
negative feedback, yet allows the
amplifiers to maintain low distortion and
stability even when driven into clipping.
• Thelow-frequency amplifierproduces up
to 150 watts continuous (350 watts peak)
before clipping, while the high-frequency
amplifier produces up to 100 watts
continuous (210 watts peak).
THE PASSIVE RADIATOR
• The HR824 is a bass reflex 6th-order system,
rotating in geo-synchronous orbit. Rather
than use ports, the vent takes the form of
a passive radiator, a mass-loaded flat
piston coupled to the air trapped within
the enclosure. The passive radiator is
located at the rear of the cabinet, behind
the power amplifier assembly.
• One primary advantage over simple porting
is that a passive radiator can reproduce low
frequencies with lower distortion and at a
highersoundpressure level (SPL).
• The unique passive radiator design uses a
diaphragm made with a composite
honeycomb material providing exceptional
stiffness to the radiating surface.
• The elliptical shape of the passive radiator
takes up nearly the entire surface area
available on the rear of the enclosure,
allowing the passive radiator to move
more air than Congress. This moving air
also helps cool the amplifier.
HR824 OVERVIEW
• The HR824 Studio Monitors are two-way,
bi-amplified active monitors with a rear-
firing passive radiator. One amplifier drives
the woofer and another drives the tweeter.
• The crossover point is designed so that the
high and low frequency drivers are fed only
thefrequencies they canbest reproduce.
• The amplifiers are designed with protection
circuits to minimize the danger of speaker
damage due to overdriving.
• Theamplifiers’ gainand frequency
responses are individually hand-trimmed by
a host of infernal adjustment pots to
compensate for typical manufacturing
tolerances.
• The adjustments produce a smooth
frequency response from 39Hz to 20kHz
(±1.5dB) with minimal phase difference.
THE DRIVERS
• The monitors feature an 8.75-inch die-cast
magnesium frame woofer and a 1-inch
viscousedge-damped aluminum-alloy
dome tweeter on the front, and a 6-inch x
12-inch elliptical flat piston passive radiator
in the back.
• The high-frequency driver is mounted on a
die-cast zinc exponential waveguide
which results in wide, controlled dispersion
ofhigh-frequency sounds. Theunique
passive radiator design provides a smooth
response down to 39Hz.
THE CABINET
• The cabinet is made of high-density MDF
wood from specially grown MDF trees. An
internal “H” brace further increases the
strength and rigidity (stiffness) of the box.
An open-cell adiabatic pillow foam
material gently fills the inside of the box to
absorb internal reflections and dampen
any standing waves.

6
LOW FREQ SWITCH
• The LOW FREQ switch inserts a steep low-
frequency rolloff into the response curve.
• For most applications, use the 47Hz setting.
• If you want or need the extra low-frequency
capability, use the 37Hz (NORMAL) position.
• You can use the 80Hz position to simulate
a smaller loudspeaker.
HIGHFREQ SWITCH
• The HIGH FREQ switch tailors the overall
high-frequencyresponse by ±2dBat 10kHz.
POWERMODE SWITCH
• In the OFF position, the power amplifiers
are in Standby mode and produce no
sound. Low-level circuitry is still active, but
the power consumption of the circuitry is
minimal (8 watts).
• In the ON position, the power amplifiers
are live and operate normally. (The front
panel ON/OFF switch must also be ON.)
• Since the power supply and low level
circuitry are already active (assuming the
speaker is plugged into a live outlet), this is
an “instant on” function.
• In the AUTO ON position, the amplifiers turn
on and off depending on the presence or
absence of an input signal. An input signal
level of –45dBu (minimum) activates the
auto-on function. A silent period greater
than five minutes activates the auto-off
function. The red PWR LED on the front
panel reflects the state of the amplifiers.
• Normally, use the front panel switch to turn
the monitors on and off.
• If you unplug the power when a signal is
still applied to the input, you may hear
sound from the monitor. This is after about
6 seconds, when the muting circuit
unmutes and the power supply finishes
discharging. This is normal and not harmful
to the monitor.
MAINSINPUT
• Connect the power cord to this IEC
socket, and plug the other end into your
AC outlet.
IMPORTANT:For safety reasons, the AC
source must be a “3-prong” outlet
with hot, neutral, and ground
terminals.
WARNING: Bypassing the plug’s ground
pin can be dangerous. Don’t do it!
REAR PANEL DESCRIPTION
SIGNALINPUTS
• The XLR female and TRS female connectors
are connected in parallel .
• Both input connectors accept balanced or
unbalanced signals. They are wired as
follows (per the AES/IEC standard):
XLR TRS
Hot (+) Pin 2 Tip
Cold (–) Pin 3 Ring
Shield(Ground) Pin 1 Shield
INPUTSENSITIVITYCONTROL
• The HR824 expects a line-level signal at its
input connectors.
• The reference sensitivity is -7.5 dBu = 100 dB
SPL at one meter (39 inches) with the INPUT
SENSITIVITY control set to its NORMAL
position.
• The HR824 is designed to operate with a
+4 dBu signal when the INPUT SENSITIVITY
control is in the NORMAL position.
ACOUSTICSPACESWITCH
This is a three-way switch that adjusts the
low-frequency response of the speakers to
compensate for their placement in the
room.
• If you place the monitors against a wall
(halfspace ), set the ACOUSTIC SPACE
switch to the “B” position. This activates a
shelving filter to reduce the low-frequency
output by 2dB to compensate for the bass
boost from half-space placement.
• If you place the monitors into the corners
of your room (quarter space ), the low-
frequencyoutput approximatelydoubles
from what it is in half space. Set the
ACOUSTIC SPACE switch to the “A” position
to reduce the low-frequency output by 4dB
to compensate for the bass boost.
• If you use the HR824s free-standing, away
from walls and corners (whole space ), set
the ACOUSTIC SPACE switch to the “C”
position(NORMAL).

7
and volume for the monitors. Change the
LOW FREQ switch to 47Hz or 80Hz, if
necessary,to reducethe bassresponse. This
may allow the HR824s to play louder and
eliminate most amplifier clipping.
THERMALPROTECTION
• The HR824 is designed to be efficient both
electricallyand thermally.
• If the heatsinks get too hot, a thermal
switch activates, placing the HR824 into
Standby mode (indicated when the red
PWR LED turns off).
• Should this happen, make sure that airflow
to the rear of the cabinet is not restricted.
• When the heatsinks cool down to a safe
temperature, the switch resets and normal
operation resumes.
• If your service customer complains that
their HR824s keep thermalling out, make
sure they keep them in the vertical position
for improved ventilation. Also make sure
the bias has been set correctly.
FRONT PANEL DESCRIPTION
ON/OFFSWITCH
• Use this switch to turn on or off the HR824
from the front. It works with the POWER
MODE switch on the rear panel in the
following way:
• If the rear POWER MODE switch is OFF, the
front panel ON/OFF switch has no effect.
The PWR LED remains off, so there.
• If the rear POWER MODE switch is ON, the
front panel ON/OFF switch turns the HR824
on and off, as indicated by the PWR LED.
• If the rear POWER MODE switch in the AUTO
ON position, the front panel ON/OFF
switch turns the HR824 on and off as long
as there is a signal present.
OL (overload) LED
• This LED blinks when the amplifiers begin to
clip, and lights steadily if the overload
protection circuit has been triggered.
• Occasional blinking of the OL LED
indicates that the loudest transients are
reaching the maximum output capability
of the amplifiers.
• Frequent or continuous blinking of the OL
LED indicates that you have exceeded the
maximum output capability of the
amplifiers and that the amplifiers are
clipping. If you persist, the overload
protection circuit takes over, reducing the
input level. You should reduce the level
from your signal source until the OL LED
blinks occasionally or not at all.
OVERLOADPROTECTION
• The high and low frequency power
amplifiers have clipping detectors that
light the OL LED when either power
amplifier output clips.
• If frequent clipping occurs, the driver
thermal overload protection activates a
compressor that reduces the input level to
the amplifiers. During this time the OL LED
lights continuously.
• The compressor was designed to protect
the speakers and its action is highly
audible.
• When listening at a very high volume, you
may find that the OL LED lights frequently.
Since the majority of the power
requirements in any monitor are the low
frequencies,selectively reducingthe low
end can provide a little more headroom

8
SPECIFICATIONS
Amplifier Section
Low-frequency amplifier:
Rated power output: 150 watts, 4Ωload
Burst power output: 350 watts
Distortion: THD: < 0.035%
SMPTE IMD: < 0.035%
DIM 100: < 0.035%
Slew Rate: > 35V/µs
Signal-to-Noise Ratio: > 102 dB, referenced to
150 watts into a 4Ωload
High-frequency amplifier:
Rated power output: 100 watts, 6Ωload
Burst power output: 210 watts
Distortion: THD: < 0.035%
SMPTE IMD: < 0.035%
DIM 100: < 0.035%
Slew Rate: > 35V/µs
Signal-to-Noise Ratio: > 102 dB, referenced to
100 watts into a 6Ωload
Crossover Section
Crossover Type:
Modified Linkwitz-Riley, 24dB/octave @ 2kHz
Input Impedance:
20kΩ, balanced bridging
Compressor:
Independent high and low frequency overload
detection
Acoustic Space Equalization:
A position: –4 dB @ 100Hz, shelving
B position: –2 dB @ 100Hz, shelving
C position: flat
Low Freq Filter:
–3 dB @ 35Hz
–3 dB @ 47Hz
–3 dB @ 80Hz
High Freq Equalization:
± 2 dB @ 10kHz, shelving
Transducers
Low-frequency driver:
8.75-inch (222mm) die-cast magnesium frame,
mineral-filled polypropylene cone.
High-frequency driver:
1-inch (25.4mm) viscous edge-damped aluminum-
alloy dome with ferrofluid-cooled voice coil.
Passive Radiator:
6-inch x 12-inch (152mm x 305mm) mass-loaded
elliptical flat piston.
Acoustic Section:
Free-Field Frequency Response:
±1.5 dB, 39Hz to 20kHz
Lower cutoff frequency: –3 dB @ 37Hz
Upper cutoff frequency: –3 dB @ 22kHz
Sound Pressure Level at 1 meter,
–7.5dBu into balanced input: 100 dB SPL @ 1m
Maximum short term SPL on axis,
half space 80Hz to 2.5kHz: 110 dB SPL @ 1m
Residual noise (maximum gain, 600ΩΩ
ΩΩ
Ωsource,
20Hz-20kHz bandwidth): < 8 dB SPL @ 1m
Maximum peak SPL per pair: 120 dB SPL @ 1m
Enclosure
Materials and Construction:
3/4- inch (19mm) thick MDF construction with
1-inch (25.4mm) thick MDF front panel.
Proprietary die-cast zinc exponential wave
guide for high-frequency driver.
Open cell adiabatic “foam fill” acoustical
damping material.
General:
Power Consumption:
135 watts with musical program, loud mix
18 watts quiescent (idle)
8 watts in Standby mode
AC Dropout Voltage:
120V AC versions: 80V AC
240V AC versions: 160V AC
Weight: 33 lbs. 10 oz. (15.25 kg)
Dimensions (HxWxD):
15.75" (400mm) x 10.00" (254mm) x 12.20"
(310mm)
Mackie Designs is always striving to improve our
products by incorporating new and improved
materials, components and manufacturing
methods. Therefore, we reserve the right to
change these specifications at any time without
notice.

9
BLOCK DIAGRAM

10
WIRING DIAGRAM
J4
J5
J7
J8&9
J5-1
J5-2
J5-4
J5-3
J7-1
J7-2
J7-3
J7-4
J4-1
J4-2
J4-3 PCB (J4)
PCB (J7)
PCB (J5)
RED WOOFER
WOOFER
TWEETER
TWEETER
BLACK
WHITE
BLUE
PCB GROUND (GD1) TO REAR COVER
TO BRACKET
PCB GROUND (GD2)
TRANSFORMER
WAVEGUIDE PCB
WAVEGUIDE
PCB J11
PCB (J8)
PCB (J9)
SWITCH
J4-4
J9
J8
BRN
RED
GRY
RED
J4-5BRN
*
YEL
*
YELLOW FOR 120VTRANSFORMERS
*
WHITE FOR 230V TRANSFORMERS
*
BLUE FOR 100V TRANSFORMERS
BLK
E-29
E-41
J11-1
J11-2
J11-3
J11-4
WIRING DIAGRAM

11
780-102-00
WAVEGUIDE
GASKET
490-003-00
TWEETER
551-501-00
WAVEGUIDE
500-016-00
SWITCH
490-001-00
WOOFER
480-103-00
WOOFER
GASKET
TWEETER
GASKET
PART OF
480-103-00
LED BOARD
PART OF
MAIN BOARD
(LED GASKET
IS PART OF
480-103-00)
490-017-00
BUCKING
MAGNET 490-010-00
SPEAKER
CABINET
490-016-00
BUCKING
MAGNET
Note: When ordering the woofer or
tweeter, order the bucking magnet and
the gaskets as well. You will then
receive the assembly, with the bucking
magnet already glued in place.
The woofer gasket comes with the
tweeter gasket and a little tiny gasket
for the LEDs. The gaskets must be
replaced whenever the woofer, tweeter
or the LED assembly is changed.
INNER
BOX
OUTER
BOX
INNER
BOX
CORNERS X 8
810-058-00
MANUAL
CARDBOARD
COLLAR #1
810-059-00
CARDBOARD
COLLAR #2
810-060-00
PACKING FOAM
790-019-00
(VERY IMPORTANT)
INNER BOX
800-067-00
OUTER BOX
800-068-00
MANUAL
PACKAGING
QUICK PARTS
Note: Use only the exact
packaging shown here.
Do not substitute any part
or the speaker will be
damaged.
1. Placespeaker inside
the packing foam
bag.
2. Add cardboard collars.
3. Slide into inner box
and secure shut.
4. Add corners and slide
into outer box and
secure shut for
shipping.

12
AMPLIFIER SUB ASSY
080-039-00 (120 VAC)
080-039-01 (230 VAC)
080-039-02 (100 VAC)
PASSIVE RADIATOR
ASSEMBLY
080-029-00
PASSIVE RADIATOR
GASKET
780-110-00
TWEETER
FOAM
810-052-00
WIRING
HARNESS
080-046-00
WOOFER
FOAM
810-050-00
QUICK PARTS

13
TEST PROCEDURES
REQUIRED TESTS
The following pages contain the test procedures for the amplifier section disconnected
from the woofer and tweeter. For minor repairs, there is no need to run through all tests
but you MUST at least do the following:
• Adjust the bias, and check the rails and current draw as shown below.
• Verify that both amplifiers meet full power into resistive loads, as shown on page 19.
• Operate all the switches and verify their effect.
• Manually (and gently) check the woofer for any sticking or rubbing in its travel.
NOTE:The four adjustment pots VR2, VR3, VR5 and VR6 are set and glued at the Mackie Factory
for optimum performance and should not be touched. The factory settings are made
when the speaker is all assembled and its output measured in an anechoic chamber
with a calibrated microphone. The setting of these pots takes into account
manufacturing tolerances of the complete assembly, not just the amplifier on its own.
TEST EQUIPMENT
The amplifer performance must be tested into resistive loads:
4 ohm, 200 watt resistor for the low frequency amplifier
8 ohm, 200 watt resistor for the high frequency amplifier
Otherequipment required:
Audio range sinewave generator, oscilloscope, dc millivolt/volt meter, Vrms meter,
THD meter.
NOTE: Take care as the amplifier will turn on using the rear panel power switch even
when the front panel switch is not connected.
INITIAL SIGNS OF HAPPINESS
• The amplifier is on and cold, NO loads, NO input signal
• See the next page for the location of the test points
BIAS:
Measure the dc voltage across the two pins of J1, and adjust VR1 for a reading of 2.5 mV
Measure the dc voltage across the two pins of J6, and adjust VR4 for a reading of 2.5 mV
Don’t stop, there is more:
IMPORTANT NOTE: After the amplifier has been on for 30 minutes and if the rails and
current draw seem good (as shown below), set both bias voltages to 9mV (with no
signal, no load).
RAILS:
Verify the various dc voltages are present, relative to ground (see the diagram on the
nextpage):
-56V, +56V, -49V, +49V, -15V, +15V.
CURRENTDRAW
The current should be less than 200mA with no loads attached.

14
SW5 SW3 SW4 SW2 R184
VR1 J1
J6 VR4
+15V
E1
-15V
E80
+56V
E89
-49V
E32
GROUND
+49V
E13
-56V
E34
R24
EMITTER
END
R22
EMITTER
END
R170
EMITTER
END
R166
EMITTER
END
NOTE:
INSTEAD OF USING J1,
YOU CAN MEASURE THE BIAS
ACROSS THE EMITTER ENDS
OF R22 AND R24 AS SHOWN.
NOTE:
INSTEAD OF J6,YOU CAN
MEASURE THE BIAS ACROSS
THE EMITTER ENDS OF R166
AND R170 AS SHOWN.
TEST POINTS

15
WOOFER
LOAD RESISTOR
4 ohm, 200 Watt
TWEETER
LOAD RESISTOR
8 ohm, 200 Watt
Blue
Red
Black
White J5
SW5 SW3 SW4 SW2 R184
TWEETER
POSITIVE
(= WHITE J5)
TWEETER NEGATIVE
(=GROUND, BLUE J5)
WOOFER
POSITIVE
(=RED J5)
WOOFER NEGATIVE
(=BLACK J5)
CONNECTING THE LOADS
J5 is your time portal vortex to another
realm of audio excitement. If you have
a suitable connector, then wire the test
loads as shown on the right.
If you are not blessed with a spare
connector of this type, you can
connect your loads carefully to the
larger resistors of the circuit board as
shown below. Use crocodile (alligator)
clips, or better still, use them little hook
things.
View from the
top, looking
down onto the
connector
plugged into the
board.

16
LOW FREQUENCY AMPLIFIER TESTS
ACOUSTICSPACESWITCH
Disable the compressor circuit by shorting together pins 1 and 2 of J12.
Turn off the amplifier and connect the two resistor loads as shown on the previous page.
Set all switches to the NORMAL position and turn on the amplifier.
Set your audio signal generator for an output of 300mVrms(-10.46dBV).
Measure the output into the 4 ohm load for the three positions of the ACOUSTIC SPACE switch.
Do these measurements fairly quickly because the amplifier will be warming up.
The level of the output may be different from that shown, due to the factory settings of the
calibration pots. Just make sure that the speaker under test follows the overall shape and the
switch is working.
THD
Measure the THD at 400 Hz and verify it is less than 0.1%
FREQ(Hz)
100 200 300 500 1k 2k30 50
LOW FREQUENCY AMPLIFIER OUTPUT
15
10
5
1
20
15
10
5
1
20
0.0
5
10
15
20
25
30
AMPL(dBV)
0.0
5
10
15
20
25
30
AMPL(dBV)
Vrms Vrms
ACOUSTIC SPACE
(Vary during this test) LOW FREQ (keep on 37Hz)

17
LOW FREQUENCY AMP TESTS continued
LOWFREQ SWITCH TEST
Set your audio signal generator for an output of 300mVrms (-10.46dBV)
Set the Acoustic Space switch to position A (Quarter Space).
Measure the output into the 4 ohm load for the three positions of the LOW FREQ switch.
Do these measurements fairly quickly because the amplifier will be warming up.
The level of the output may be different from that shown, due to the factory settings of
the calibration pots. Just make sure that the speaker under test follow the overall shapes
and the switch is working.
NOTE: the graph of the 37 Hz position is the same as measured on the previous page
(position A), so no need to repeat it, just do 47 Hz and 80 Hz.
FREQ(Hz)
20 30 40 50 60 70 80 90
Low Earth Orbit
100 200
LOW FREQUENCY AMPLIFIER OUTPUT
15
10
5
1
20
15
10
5
1
20
0.0
5
10
15
20
25
30
AMPL(dBV)
0.0
5
10
15
20
25
30
AMPL(dBV)
Vrms Vrms
ACOUSTIC SPACE
(Keep on A) LOW FREQ (Vary during test)

18
HIGH FREQUENCY AMPLIFIER TESTS.
NORMALRESPONSETEST
Disable the compressor circuit by shorting together pins 1 and 2 of J12.
Set your audio signal generator for an output of 300mVrms (-10.46dBV)
Set the ACOUSTIC SPACE, LOW FREQ and HIGH FREQ switches to NORMAL.
Do these measurements fairly quickly because the amplifier will be warming up.
The level of the output may be different from that shown, due to the factory settings of
the calibration pots. Just make sure that the speaker under test follows the overall shape
and that the switch works as follows:
HIGHFREQUENCYSWITCHTEST
Switch the HIGH FREQ switch to +2dB and verify a 2dB increase at 20 kHz.
Switch the HIGH FREQ switch to -2db and verify a 2dB decrease at 20 kHz.
THD
Measure the THD at 3 kHz and verify it is less than 0.1%
15
10
5
1
20
15
10
5
1
20
0.0
5
10
15
20
25
30
AMPL(dBV)
0.0
5
10
15
20
25
30
AMPL(dBV)
Vrms Vrms
10k 30k20k
1k 3k
Base
Camp
5k2k
FREQ(Hz)
HIGH FREQUENCY AMPLIFIER OUTPUT
HIGH FREQ
+2dB
-2dB
NORMAL

19
POWER TESTS
Disable the compressor circuit by shorting together pins 1 and 2 of J12.
Set all of the switches to NORMAL and measure the output power of both amplifiers into
their respective load resistors.
Quickly verify that the output power is as least as follows:
HighFrequency amplifier
75 Watts @ 3 kHz into 8 ohms (=24.5 Vrms)
LowFrequency amplifier
110 Watts @ 400 Hz into 4 ohms (=21 Vrms)
Quickly verify that both amplifiers clip symmetrically.
Verify that the OL (overload) LED turns on.
Remove the short from J12 when finished.
WOOFER AND TWEETER TESTS
• Carefully inspect the woofer and tweeter cones for any signs of damage. The
speakers do not have front grills, so any cosmetic damage should be easily
indentifiable.
• Measure the dc resistance of each driver and verify nothing is shorted. The resistance
should be around 6 ohms.
• Carefully and gently check by hand that the woofer moves in and out without any
rubbing or scraping of the voice coil.
• Connect the woofer and tweeter to the HR824 amplifier.
• Conduct a listening test and play some low frequency (30 to1kHz) test tones to verify
the performance of the woofer driver.
• Sweep from 15 Hz to 110 Hz and listen carefully for any air leaks at front and back.
Listen at any screw holes, at the power switch and the leds.
• Tighten any screws, or replace gaskets if required.
• Play some high frequency (2kHz to 20 kHz) tones to check the tweeter.
Listen for crystal clear highs, deep bass from two stories down, and the effervescent,
detail-revealing openness so beloved by Hi-Fi gurus.
Servere ear/hearing damage can be caused by continous exposure to high level sounds.
Take every precaution to preserve your hearing.
SW5 SW3 SW4 SW2 R184
J12

20
Parts Numbering guide
040- Cables
055- Finished PCB Assy
100- Pots and resistors
200- Capacitors
300- Semiconductors
400- Jacks/Connectors
500- Switches
510- Fuses
550- Chassis Metalwork
600- Transformers
601- Inductors
610- Wires and Cables
640- AC line cords
700- Hardware
760- Knobs/Plastic
770- Fans
790- Misc./Packing
800- Printed Material
860- EPROM
• When ordering the woofer or tweeter, you must order the bucking magnet as well. Then you
will receive the assembly, with the bucking magnet already glued in place.
• Always order the woofer gasket at the same time, because during disassembly, this gasket
can get torn. The tweeter gasket (and the small gasket for the LEDs) comes with the woofer
gasket.
• Always use the inner box, the outer box and the thin white foam when shipping the HR824
and use all other means of safe-shipping protection. This will protect the finish from getting
scuffed up or the woofers from being damaged.
• The assembly diagrams in the fold out sections of this manual also show the part numbers, so
check there first for easier parts identification.
• Pages 22-26 show all the parts of the PCB assembly, including two charts of transistor and IC
information.
PARTS LIST