Shure Pro Master 700 User manual

Price $1 0.00
700 AND 706 SERIES
SERVICE MANUAL
Manufacturedby
SHURE BROTHERS INC.
222 HartreyAvenue
Evanston,Illinois
60204 U.S.A.
Copyright 1981, Shure Brothers Inc.
AL663 (Al) 27A8027
Printed in U.S.A.

SPECIFICATIONS*
Type ................ .Solid-state power console using
discrete components and inte-
grated circuits
Inputs
............... .Six input channels (high andlor
balanced low impedance), plus
two aux input channels (7
and
8)
lnput Channel Controls.VOLUME, INPUT ATTENUATOR,
A/B PAN (700), LOW and HlGH
FREQUENCY EQUALIZATION,
EFFECTSIREVERB, MONITOR
Aux Channel Controls.
. .VOLUME, A/B PAN (700)
MasterControls.
...... .MASTER, EFFECTS SEND, RE-
VERB LOW and HlGH EQUAL-
IZATION, REVERB RETURN,
MONITOR MASTER
Outputs
............. .SPEAKER, MONITOR, EQ OUT,
MIX OUT, EFFECTS, HEAD-
PHONES, AUX, MIC
Common Mix Buses
... .MIX OUTPUT, EQ OUTPUT (A, B
in 700)
Reverb andEffects
..... Built-in reverberation unit; provi-
sions for connection to remote
reverb on-off switch and exter-
nal effects devices
Graphic Equalizers.
... .lo-band, fully combining, mini-
mum-phase, octave type, nor-
mally connected to power am-
plifier input; 13 dB boost or cut
at 63, 125, 250, 500 Hz, 1, 2, 4,
8 and 16 kHz; BELOW 63 Hz 12
dB/octave cutoff filter (10 dB
down at 31 Hz)
LEDStatus Indicators.
.. INPUT CLIP, DB PEAKIfeedback
frequency, PA OVERLOAD,
POWER, TEMP WARNING,
SHUTDOWN
706; 700 with 700 with
both channels one channel
Power Output driven driven
Per channel/4 ohms 200W min. 240W typical
Perchannel/8 ohms 125W min. 145Wtypical
Measured at 1kHz, 120Vac, 1
% THD
Distortion
........... .THD typically less than 0.1% at
40 Hz and
1 kHz, 0.25% at 15
kHz; IM distortion typically
less than 0.25% [One channel
driven, 180W or less to
4 ohms,
110W or less to 8 ohms, mea-
sured from low-impedance in-
put with individual and master
controls at typical settings
(orange index marks)]
Low- and High-
Frequency lnput
........
Equalization
? 13 dB at 100Hz and 10kHz
lnput Clipping
.........
Indicators .Light
3 dB below input or equal-
izer clipping level
...
DB Peak Indicators.. Indicate power amplifier peak
voltage; +6 dB LED indicates
100 watts sine-wave output to
4-ohm load. Risetime: 250 @ec
to full-scale indication; fall
time: 65 msec from full-scale to
no indication
PA Overload
.........
Indicators .Light when power amplifier THD
exceeds 1
% ; fully on at 5%
Temperature Warning
..........
Indicator .Lights when output transistor
temperature exceeds 70°C
(158°F)
Shutdown Indicator
.... Lightswhen power amplifier shut-
down occurs due to output
transistor temperature over
100°C (212"F), air flow or fan
failure, or dc at speaker output
lnputSensitivity
...
(full power output). BAL LO IMP 0.6 mV
HI IMP 8 mV
AUX 21 5 mV (700)
106mV (706)
EQ INPUT 960 mV
PA INPUT 960 mV

SPECIFICATIONS* (continued)
... Input Clipping Level.
BAL LO IMP 700 mV to 21 mV
(INPUT ATTEN
-30 to 0)
HI IMP 10V to 335 mV (INPUT
ATTEN -30 to 0)
AUX 30V to 10V (VOLUME
from 0 to 10)
Voltage Gain ......... .94 dB BAL LO IMP INPUT to
SPEAKER OUTPUTS
71 dB HI IMP INPUTto SPEAKER
OUTPUTS
43 dB AUX INPUT to SPEAKER
OUTPUTS (700; 706: 49 dB)
64 dB BAL LO IMP INPUT to MIX
OUTPUT
77 dB BAL LO IMP INPUT to
MONITOR OUTPUT
74 dB BAL LO IMP INPUT to
EFFECTS OUTPUT
16 dB BAL LO IMP INPUT to MIC
OUTPUT
58 dB BAL LO IMP INPUT to AUX
OUTPUT
81 dB BAL LO IMP INPUT to
HEADPHONE OUTPUT
0 dB EQ INPUTto EQ OUTPUT
30 dB PA INPUT to SPEAKER
OUTPUTS
Levels and Impedances
Nominal Maximum Actual Working
Circuit Level Level Impedance Impedance
BAL LO IMP INPUT 5 mV 700 mV lk 19-300 ohms
HI IMP INPUT 50 mV 10V 145k lOOk or less
AUX INPUT 0.5V 30V 50k 10k or less
MIX OUTPUT 1V 9V 2.4k 2k or more
EFFECTSOUTPUT 1V 9V 2.4k 2k or more
MONITOROUTPUT 1V 9V 2.4k 2k or more
EQ INPUT 1V 1OV 50k 10k or less
EQ OUTPUT 1V 9V 2.4k 2k or more
AUX OUTPUT 1V 9V 5k 2k or more
MICOUTPUT 5 mV 75 mV 70 ohms 19-300ohms
PA INPUT 1V 1OV 50k 10k or less
SPEAKER OUTPUT
- 28.3V - 4 ohms or more
HEADPHONES
- 1OV 360 ohms 4 ohms or more
... Frequency Response 22dB, 40 to 20,000 Hz, BAL LO
IMP INPUT to SPEAKER OUT-
PUTS
Humand Noise
.... (20 Hz to 20 kHz). -127 dBV equivalent input (BAL
LO IMP)
Noise
...
(300Hz to 20 kHz). -128 dBV equivalent input (BAL
LO IMP)
.. Signal-to-Noise Ratio .Greater than 80 dB (below full
output) at typical control set-
tings (orange marks, MASTER
at 5, INPUT ATTEN at -12)
Mic lnput Simplex
............ Power .24 Vdc open-circuit, 1.8k series
resistance, simplex onloff
switch
.. Power Requirements .Models 700 and 706: 120 Vac
f lo%,50160 Hz; 1100W (700),
600W (706) max. (Can be re-
wired for other voltages; see
OPERATION AT OTHER VOLT-
AGES);
Models 700E6 and
706E6: 100, 120, 140, 200, 220
and 240 volts, 50160
Hz (switch-
selectable).
Environmental
Conditions
Operating
......... .-7" to 43°C (20" to 110°F)
Storage
........... .-40" to 74°C(-40" to 165°F)
Overall Dimensions.
... .l9O mm H x 584 mm W x 508 mm
D (7% in. x 23 in. x 20 in.)
Weight
.............. .700: 21.3 kg (47 Ib)
706: 17.9 kg (39% Ib)
Construction ......... .Molded construction with black
finish, carrying handle, molded
rubber feet, linecord storage
Certifications
........ .Listed by Underwriters' Labora-
tories, Inc.; listed by Canadian
Standards Association as Cer-
tified (700, 706)
*Measurement Conditions (unless otherwise specified): All volume and gain
controls for measured channel at maximum; unused channel controls at 0;
equalization controls at 0. Measured input terminated as follows (unused
inputs unterminated): BAL
LO IMP, 150 ohms; HI IMP, 33k; AUX. EQ and PA.
4.7k. All outputs terminated as follows: all high-level outputs. 47k; MIC,
150 ohms; SPEAKER,
4 ohms: HEADPHONES, 200 ohms.

TABLE OF CONTENTS
Section Page
SPECIFICATIONS ............................... ii
DESCRIPTION .................................. vii
MAINTENANCE
................................. 1
TROUBLESHOOTING ............................ 1
CIRCUIT OPERATION
............................ 2
PA Overload LED Indicators ..................... 2
DBPeakIFeedback FinderTM LEDS ............... 3
Feedback Finder .............................. 3
............... PowerAmplifier ProtectionCircuits 3
SERVICE INSTRUCTIONS ........................ 4
ReplacementParts ............................. 4
FuseReplacement ............................. 4
External Parts ................................. 4
Service Access ............................... 4
Reverb Pan Assembly .......................... 6
PrintedCircuit Boards .......................... 6
DC Output Balance Adjustment ................. 7
DC Bias Current Adjustment .................... 7
DB Peak IndicatorsIFeedback Finder Frequency
Calibration
................................. 7
Full Wave Balance ......................... 7
DB Peak LED Calibration ................... 8
Feedback Finder Calibration ................ 8
Small Signal and Driver Transistors and
Integrated Circuits
........................... 8
Driver Transistors ............................. 8
Output Transistors ............................. 8
Diode BridgeRectifier .......................... 8
Transistor and Diode Removal ................... 8
Active Component Checking .................... 8
Printed Circuit Board Connectors ................ 9
Ferrite Bead Rings ............................. 9
SERVICE ILLUSTRATIONS ....................... 9
OPTIONAL ACCESSORIES ....................... 9
................................... GUARANTEE 9
SHIPPING INSTRUCTIONS ....................... 9
OPERATION AT OTHER VOLTAGES ............... 10
REPLACEMENT PARTS LIST
..................... 11
NOTES TO SERVICE ILLUSTRATIONS
............ 17

Model 700
DESCRIPTION
Model 706
The Shure PRO MASTERTM Power Consoles are port-
able, high-power, eight-input mixer-amplifiers designed for
use by professional entertainers and sound system oper-
ators. They are all solid-state units, employing the latest
developments in integrated circuit, discrete component,
and printed wiring technology. The PRO MASTER features
pre-fader monitor, and exclusive FEEDBACK FINDERTM
and PATCH BLOCKTMrear panel. Models 700 and 700E6
are stereo units, with twin 200-watt (rms) power amps, and
Models 706 and 706E6 are mono units, with
a single 200-
watt (rms) power amp.
Six input channels for microphones andlor aux level
sources provide six high-impedance and six balanced
low-impedance inputs (which can be used simultaneously).
Each input channel is equipped with volume, 0-30dB atten-
uator, high- and low-frequency equalization, effectdreverb
and monitor controls. Two additional aux (only) input chan-
nels (7 and
8) with volume controls are also provided.
Models 700 and 700E6 also contain AIB PAN controls.
LED indicators show input clipping, power amp peak
output level, power amp overload, power-on, temperature
warning, and shutdown conditions.
Master controls include: master volume, effects send,
reverb high- and low-frequency equalization, reverb return
and monitor. Console outputs are: monitor, effects, stereo
headphones, aux, mic, and speakers. In addition, common
mix buses are provided: mix output and equalizer output.
Each 10-band graphic equalizer uses minimum-phase,
combining-type octave filters. Each filter is continuously
adjustable over a 213 dB range, except for the lowest,
which is a 12 dB1octave cut-only switch. The FEEDBACK
FINDER circuit switches the LEDs from power amp peak
output level indicators to visual indicators of feedback
frequency for eliminating feedback by graphic equalizer
adjustment.
The built-in electromechanical spring-type reverbera-
tion device has provisions for connecting an external re-
verb onloff switchthrough the rear panel.
The rear-panel PATCH BLOCK contains a block diagram
of the console's circuits, with patching jacks located inthe
diagramfor easy reference.
The Model 700 and 706 consoles' regulated low-voltage
power supplies operate over a 120Vac
* 10% range (oper-
ation as low as 100Vac is possible at reduced output). The
consoles can be rewired internally for operation at other
voltages (see
OPERATION AT OTHER VOLTAGES). An
unswitched ac receptacle for powering accessory equip-
ment up to 100 watts is supplied. The Models 700E6 and
706E6 operate at switch-selected voltages of 100,120,140,
200, 220 and 240 volts. Irf all models, a regulated 24 Vdc
simplex supply is provided for powering condenser micro-
phones. The consoles are protected against damage from
open- or short-circuits on inputs or outputs, against heat
damage by a cooling fan and automatic thermal shutdown
circuit, and against radio frequency interference and line
noise.
The structural foam molded cover is fastened to a
19 mm
(% in.) wood bottom panel and contains a retrac-
tile handle, rubber molded feet, and line cord storage.
Models 700 and 706 are Listed by Underwriters' Labora-
tories, Inc., and listed by Canadian Standards Association
as Certified.

MAINTENANCE
The PRO MASTERTM is an exceptionally well-designed
unit. All components are of the highest quality, operating
well within their respective ratings to assure long life. The
following list of Do's and Don'ts describes minimal operat-
ing precautions and maintenance to provide years of de-
pendable service.
DO cleanthe air filter every 100hoursof operation (more
frequently in dusty or dirty areas). Stand the console on
its rear bumpers, remove the screw securing the filter,
and slide it out of its slot. Rinse the filter inwater or a
mild detergent solution, allow to dry, and replace.
DO unplug the console before cleaning. DO clean the
outer surfaces of the console with a clean, damp cloth
and milddetergent. DON'T use strong solvents or clean-
ingfluids.
DO use a l6AWG or larger (700, 700E6; 18 AWG for 706
or 706E6) heavy-duty extension cord when additional
line cord length is needed.
DON'T operate the console with air louvers blocked, or
placed on a radiatoror heat-producing equipment. Avoid
operation in direct, hot sunlight.
DON'T replace the rear-panel fuse with a different size
or type. Use only IOA, 250V (for Model 700, or 700E6
when operated at 100, 120 or 140 volts), or 5A, 250V,
slow blow (for Model 700E6 when operated at 200, 220
or 240 volts. For Model 706, use a 4A, 250V SLOW BLOW
fuse. For Model 706E6, use a 5A, 250V fuse when oper-
ated at 100, 120 or 140 volts, or a 3.15A, 250V SLOW
BLOW fuse when operated at 200, 220 or 240 volts.
DON'T connect the A and B speaker outputs together
(700or 700E6). (See Instruction Manual for monophonic
setups.)
DON'T riskfire or shock hazard by operating the console
inrain.
DON'T use UNbalanced low-impedance microphones
with the SIMPLEX 24V switch on; turn off the switch
if not required for powering condenser microphones.
If simplex power is in use, connect unbalanced low-
impedance microphones through a line matching trans-
former (Shure A95FP) to a HI IMP INPUT.
TROUBLESHOOTING
Should any difficulty be encountered in console opera-
tion, the problem can often be traced to some simple
source such as an error in interconnection. The following
isoffered as a basic guidetothis type of problem.
PROBABLECAUSE
SYMPTOM OR CORRECTION
1
Console appearsto
beoverheating (TEMP
WARNING LEDon)
Console power
amplifiersturn off
and remain off
LED On)
Nosignal at speaker
(all console functions
appear normal)
Consolefuse blown
Oneof two inputs
onsame channel not
working properly (both
%-inchand3-pin
jacks inuse)
INPUTCLIP LED
flashing
PAOVERLOAD LED
flashes while DB PEAK
read less
than +6
1. Check air louversfor blockage
of proper air flow.
2. Check for proper speaker load
or shorted speaker cable.
3. Check air filter and clean if
necessary.
1. Check for proper air flow (fan
remains on during shutdown).
2. Check for hot air from left
louvers; console may have
overheated (see above). Wait
one minute to allow proper
cooling.
3. Turn console off for a few sec-
onds and turn back on.
4. If shutdown persists, havecon-
sole checked by qualified ser-
vice personnel.
1. Check for defective or improp-
erlyconnected speaker cables.
2. Check for improper connec-
tions to EQ or PA INPUT.
3. Check settings of channel
VOLUME and MASTERvolume
controls.
1. Replace with identical fuse.
2. Ifsecond fuse blows,have con-
sole checked by qualified ser-
vice personnel.
1. Make sure similar micro-
phones are used on both
inputs, and microphone im-
pedances match the inputs
used.
2. Make sure microphone is not
used with accessory equip-
ment on other input.
3. Make sure both microphone
switches are on.
1. Adjust INPUT ATTEN to re-
ducechannel input level.
2. Reduce input signal level at
source.
1. Check for defective (shorted)
speaker cable.
2. Check that load impedance is
nottoo low(too many speakers
connected).
Console is"dead"
(nooutput,
POWER LEDoff)
1. Check that ac power source
is "live" and that console is
plugged in.
2. Check that power ONIOFF
switch is on.
3. Check that rear-panel fuse
is good.

Two simple methods of localizing problems without
opening the console are as follows. These methods can
be used to find the abnormal console section with or with-
out test equipment. (The methods are not needed
if the
problem is obvious: SHUTDOWN, no POWER indication,
etc.)
With test equipment: Set all console controls to full
clockwise, REVERB RETURN control to full counterclock-
wise, and PAN (700) and EQ controls to center. Do not
connect a speaker or headphone load. Apply a 0.5 mV,
1 kHz test signal across pins 2 and 3 of one of the BAL LO
IMP input connectors. Normal voltmeter readings taken
at each speaker, rear-panel PATCH BLOCKTMand front-
panel HEADPHONES connector are given in Table 1.
The top row of figures indicates the voltage ineach stage
from input to output. Similarly, a 5 mV signal inserted ina
HI IMP input will check these same voltages. The other
listed inputs givevoltage indications only for those circuits
following the inserted signal. Ac voltages may vary t30%
from the values shown.
Without test equipment: Using only a microphone and
speaker, it isoften possible to isolate problem areas using
the PATCH BLOCK rear panel. The ability to bypass cer-
tain circuits and interchange channel signals provides a
No DB PEAK/frequen-
cybandLEDindicators
flashing (console
output normal)
Noconsole output;
no DB PEAK LED
indicatorsflashing
Loudnoiseor
clickswhen certain
microphonesor
cablesare used
No monitor output
(programoutput
normal)
Sound quality poor
(weak orthin)
simple but powerful tool for troubleshooting. For example,
in a 700 console a suspected channel A equalizer can be
checked by patching between the A MIX OUTPUT and
A PA INPUT jacks. The signal bypasses the equalizer, and
a talk test will immediately indicate whether the problem
has been eliminated.
Similarly, a potentially defective channel B mix ampli-
fier can be verified by patching the A MIX OUTPUT to the
B MIX OUTPUT. The presence of a "clean" signal from
channel A to the B speaker output indicates that the prob-
lem precedes the B MIX OUTPUT jack. Further patching
betweenthe EFFECTS OUTPUT and B MIX OUTPUT jacks
will isolate the problem to the B MIX amplifier.
1. Make certain FEEDBACK
FINDER switch is set to A, B,
ON or OFF (not between posi-
tions).
1. Check PATCH BLOCKTM rear
panel for improper patching.
2. Check for improper connec-
tions to EQ or PA INPUT.
3. Check settings of channel
VOLUME and MASTERvolume
controls.
1. SIMPLEX 24V switch is on
(when not needed).
2. Unbalanced cable used when
SIMPLEX 24V switch is on.
3. Check for defective micro-
phone cables.
1. Check MONITOR OUTPUT
connection to EQ or PA INPUT,
or external amplifier.
2. Make sure MONITOR and
MONITOR MASTER controls
are turned up.
3. Monitor speaker volume con-
trol (if present) may be turned
down.
1. Excessive equalization on
graphic equalizers.
2. Defective input or patching
cables.
TABLE 1. NOMINALTEST VOLTAGES
I 7- OUTPUTS I
I INPUT I Head-
'Tip or ring to sleeve.
Bal Lo Imp 0.5 mV
Hi Imp 5 mV
Aux (700) 0.15V
AUX (706) 64 mV
Eq 0.54V
PA 0.54V
The above methodsare extremely useful for saving time
inlocalizing problem areas. Inaddition, they may allow use
of the console in an emergency until repairs can be made.
Internal servicing should only be performed by qualified
service personnel.
Monitor
CIRCUIT OPERATION
Effects Mix
3.8V
3.8V
-
-
-
-
Most of the PRO MASTERTM circuitry uses conventional
operational amplifier technology, and can be serviced
using standard voltage-measurement procedures. How-
ever, certain circuits are unusual and may not be familiar
to many servicemen. This section describes these circuits
as an aid to servicing (see Figures 5-38).
PA OVERLOAD LED INDICATORS
The PA OVERLOAD LEOS (01109) are designed to
respond to error signals in their respective differential
amplifiers. The overload circuit is comprised of transistor
Q607 and associated resistors with the LED connected
across the collector and emitter of Q607.
The power amplifier assembly input is the differential
amplifier Q605-Q606, which amplifies the difference of the
signalsat the bases (the input signal to Q605 and the nega-
tive feedback signal to Q606). With small error signals
(normal power amplifier operation), the dc voltage drop
across R611 is approximately 1.6V, sufficient to keep Q607
turned on. Q607's collector-emitter voltage drop is very
low (approximately O.IV), and as long as Q607 is on, the
associated overload LED is turned off.
When the differential amplifier input signals differ
greatly (such as when clipping or V-l protection takes
place), the ac signal across R611 increases rapidly. At
about 1% distortion, the large ac signal through R611
causes Q607 to turn off. With Q607 turned off, the current
flow is through the associated LED and R616 to ground,
lighting the LED.
Aux
2.7V
2.7V
-
-
-
-
Mic
0.54V
0.54V
0.54V
0.54V
-
-
Eq
0.54V
0.54V
0.54V
0.54V
-
-
Speaker
7.0mV
7.0mV
7.0mV
7.0mV
-
-
phones*
0.54V
0.54V
0.54V
0 54V
0.54V
-
18.OV
18.OV
18.OV
18.OV
18.0V
180V
11.5V
11.5V
11.5V
11.5V
11.5V
11.5V