Service Manual AMS8100 Automatic Microphone Mixer
Contents
1. SHURE AMS8100 Automatic Microphone Mixer Characteristics General The AMS8100 is an automatic microphone mixer using Shure s patented Directional Intellimix that activates only those microphones being addressed minimizing poor audio caused by multiple open micro phones Each AMS8100 is an eight channel microphone mixer capable of handling up to eight AMS microphones and two aux level sources and can be expanded for installations as large as 400 input channels The AMS8100 microphone mixer works only with Shure AMS microphones and can be linked with Shure s SCM810 and FP410 automatic mixers Controls and Connectors lB Zep Sees gt BGS AUX INPUT MASTER PHONES 425 Cie 6 iC Ope oF 90 120 VAC 50 60 Hz 200 mA ween Tui LINK IN ourPuT EEJ Cay ooo ooo it a our NA e E 4 1 Low Cut Filter 1 8 11 Power Connector and Rocker Switch 2 Microphone Channel Gain Controls 1 8 12 Microphone Logic Pin 3 Input LEDs 1 8 a 13 DIP S2. The microphone preamps convert the current signals from the two microphone elements of an AMS microphone into voltage signals The microphone preamps are only suitable for use with Shure AMS microphones Conventional balanced microphones usually have about a 150 Q impedance and supply a small voltage for a conventional micro phone to amplify However AMS microphones are unbalanced have two microphone capsules per microphone have high impedance outputs and supply a current output Each output from the AMS microphone taken between the red conductor and shield and between the black conductor and shield has an approximate equivalent output impedance of 51 kQ U801 and associated components form two identical preamps one for the front microphone capsule and one for the rear microphone cap sule Both channels are simple current to voltage converters with R8015 and R8014 determining the gain Bias for the microphones is supplied from the 7 5 Vdc supply via R8012 and R8009 L801 L804 R8001 R8002 and C801 C802 form a broadband rf filter to keep rf from getting into the subsequent circuitry After the microphone preamp the signal from the front microphone element from the U801B output goes through the equalizer EQ and then the channel fader gain stage This gain stage comprised of U812A and associated components has a gain of 32 dB 40 times Following the channel fader stage is a buffer U803B that has a gain of 0 dB 1
3. JFET high impedance between their source and drain pins Q925 also switches U902B which takes R9087 out of the circuit 10 25A1041 RA Shure AMS8100 Automatic Microphone Mixer Disassembly and Assembly Observe precautions when handling this static sensitive device CAUTION Voltages in this equipment are hazardous to life No user serviceable parts are inside Refer all servicing to qualified service personnel The safety certifications of the AMS8100 do not apply when the operating voltage is changed from the factory setting WARNING Front Panel Pots In this state of disassembly most components can be accessed and the mixer can be powered and work properly To replace front panel pots 1 2 3 4 on 25A1041 RA Do not remove any of the snap in LEDs from the front panel Remove the top and bottom covers Remove the six nuts behind the front panel Remove the two nuts and washers on the front panel phone jacks Remove the four screws holding the front panel to the chassis Carefully lift the front panel out of the way with the snap in LEDs still connected Loosen the pot to be replaced Desolder the pot lift it out and install new pot Reassemble the unit in reverse order 11 Disassembly and Assembly Shure AMS8100 Automatic Microphone Mixer Front Panel Phone Jacks 1 2 3 Disassemble as above through step 6 Remove all nuts holding pots to
4. NPO dielectric types with a 100 V capacity and a 5 toler ance and polarized capacitors are tantalum or electrolytic types Table 1 Replacement Parts Reference Shure Part Designation Description Number Al Printed circuit board assembly 90A8667B C953 954 Capacitor leaded 3300 uF 20 35V 86PD8982CD F901 Fuse holder 5 x 20 mm 80A8008 J102 202 302 402 502 602 702 802 906 907 Phone jack stereo 18mm 9528322 J902 903 Connector Mini Din 95A8224 J908 909 Connector 187 spade 56A8064 JF905 Connector and ribbon cable assy 95K8697G LED101 201 301 401 501 601 701 801 901 LED bi color green red 95A8619 LED902 LED bargraph 10 segment 86A8972 SW801 901 Switch slide 3 position DPTT 55A8022 SW902 Switch side actuated DIP 7PST 55F8052 SW903 Switch rotary voltage selector 55A8054 T901 Transformer power 51E8056 Line cord ac 2m 6 ft 7 inches w1 AMS8100 Line cord ac 2 5 m 8 ft 4 inches w2 AMS8100E 19 Replacement Parts and Drawings Shure AMS8100 Automatic Microphone Mixer Reference Designation Table 2 Surface Mount Components Shure Part Number D100 102 105 107 109 115 116 200 202 205 207 209 215 216 300 302 305 307 309 315 316 400 402 405 407 409 415 416 500 502 505 507 509 515 516 600 602 605 607 609 615 616 700 702 705 707 709 715 716 800 802 805 807
5. ground and turning the channel on The GATE circuitry is comprised of U802B Q901 near 25 pin connector and its associated components When current flows through U808 channel on current also flows through R8057 which creates a voltage across R8057 When this voltage goes above about 150 mVdc U802 pin 7 is higher than U802 pin 6 causing U802B s output to go high impedance When the channel is off U802B s output is clamped to ground When this happens R8041 and R8042 provide current to Q901 s base to turn Q901 on R8043 provides hysteresis so that U802B does not buzz when turning on or off The mix stage mixes the audio from the channels to go to the output stage Link A is the gated audio signal from the output to the optoisolator for each channel Each channel has a 4 99k resistor following the opto isolator after this resistor is Link A When a new channel turns on the impedance of Link A drops because of the additional 4 99k resistors on the bus This lowering of impedance drops the audio level on Link A This effect performs the number of open microphones attenuation NOMA As more microphones come on the level of audio coming out of the mixer should be dropped R9125 and R9126 are grounded via Q926 when mixers are unlinked These resistors set the proper impedance for Link A U904A is a non inverting gain stage that feeds the signal to the master stage Link B operates similar to Link A except that the aud
6. the Link F bus so that U803D can never turn on 6 25A1041 RA Logic Circuitry 25A1041 RA Shure AMS8100 Automatic Microphone Mixer GATE 1 GATE 3 GATE 5 GATE 7 LOGIC MUTE 1 MUTE 3 MUTE 5 MUTE 7 GROUND O RIDE 2 O RIDE 4 O RIDE 6 O RIDE 8 ss essdgsssdsss VEVPTPPPR ERR MUTE 2 MUTE 4 MUTE 6 MUTE 8 GATE 2 GATE 4 GATE 6 GATE 8 O RIDE 1 O RIDE 3 O RIDE 5 O RIDE 7 Figure 2 Logic connector The logic circuitry allows a user to remotely force individual micro phones off or on or to get a signal as to which microphone is turned on The user accesses these functions via the Microphone Logic 25 pin con nector on the rear of the unit The MUTE to force a microphone off and OVERRIDE to force a microphone on inputs are standard transistor transistor logic TTL compatible inputs that are active when pulled low below 0 8 Vdc The GATE output is an open collector transistor output tied to 5 Vdc through 10 kQ The GATE terminal goes low sinks current when a channel is on The MUTE terminal for each channel goes through a 3 01 k resistor and a 047 uF capacitor near the 25 pin connector before going to the channel circuitry These are to bypass rf U802D and its associated components form the main MUTE circuitry When the MUTE signal is pulled low D804 pin 1 and pin 3 are pulled low This allows U802 pin 11 to drop to 2 0 Vdc
7. the pot bracket From the bottom of the printed circuit board pcb remove the three screws and two standoffs holding the pot bracket to the pcb Slide the pot bracket forward and remove it Replace the jacks and reassemble the unit in reverse order Rear Panel Connectors 1 2 Disassembly and Assembly Remove the top and bottom covers Remove the four screws from the front panel that hold the front panel to the chassis Remove the five screws holding the printed circuit board pcb to the chassis through the holes in the top of the chassis Remove the eight nuts and washers holding the rear panel phone jacks to the chassis Unplug the blue and brown power wires from the pcb Remove the chassis from the unit replace the parts and reassemble the unit in reverse order 12 25A1041 RA Shure AMS8100 Automatic Microphone Mixer Service Procedures Reference Material Refer to the Service Equipment Manual for standard test equipment Changing the Voltage The AMS8100 can be internally modified to operate from either 120 Vac or 230 Vac power Follow these steps to change the operating voltage 1 2 3 Disconnect the unit from the ac power source Remove the eight Phillips head screws to remove the top cover Locate voltage selector switch SW903 adjacent to the power transformer T901 Use a screwdriver to turn the center rotor to the 230 V position for 230 V operation or to the 120 V posit
8. times This buffer is used to lower the impedance of a signal fed into the direct out jack if it is modified to be a send return insert Equalizing EQ is provided to make different microphones sound similar The low frequency EQ is a single pole 6 dB per octave low cut It is a simple resistance capacitance RC filter comprised of C834 VR802 and R8147 The high frequency EQ is a boost or cut Baxandall type filter Its frequency and boost or cut amount is defined by C836 VR804 R8151 R8152 R8148 and R8149 Channel LED Circuit 25A1041 RA U807C D816 and surrounding resistors are hooked up as a full wave peak detector If the signal at D816 pin 3 reaches about 7 5 Vdc peak U807 pin 14 goes low When this pin goes low 15 Vdc Q814 conducts and pulls current through the red LED inside LED801 C826 acts as a pulse stretcher to extend the on time of the LED on peaks 3 Characteristics Shure AMS8100 Automatic Microphone Mixer Mixer Circuitry Characteristics U807B controls the green section of the LED U807B pin 1 is low 15 Vdc when the green section of LED101 is off When U802 pin 7 goes high then U807 pin 7 goes higher than pin 6 so that U807B s output goes high This turns the green LED on by pulling R8122 up on Q813 s base turning Q813 on and pushing current through LED801 Directional Intellimix The Directional Intellimix circuitry is the part of the circuit that turns a cha
9. within a 120 degree acceptance angle in front of an AMS microphone The microphone ratio circuitry is comprised of U802 U807 and associated circuitry U802A and U802B are two identical bandpass filters that allow voice band frequencies 300 Hz 5 kHz to pass through while attenuating other frequencies U807A and U807B form matched one half wave rectifiers that also convert the signal to a logarithmic dc level representing the input signal 4 25A1041 RA 25A1041 RA Shure AMS8100 Automatic Microphone Mixer VR801 is an adjustment pot that changes the dc level at U807 pin 5 effectively changing the acceptance angle of the AMS microphone This angle is factory pre set to 120 degrees which is 9 5 dB difference between the front and rear microphone capsules Maxbus The Maxbus tries to turn on only one microphone that hears the same signal If three microphones are connected to a unit and spoken into only one microphone should turn on The Maxbus circuitry is comprised of U805C U804B U803C and their associated components The rectified signal from above is fed into the Maxbus circuitry via U805C U805C steps the signal up by 6 dB 2 times if a channel is turned on The signal is then fed to U804B which connects the signal to the actual Maxbus Link D If the signal from a given channel is the highest of all the channels connected to the Maxbus then the lower half of D815 will be conducting If the
10. 809 815 816 901 902 907 909 914 917 921 923 925 927 Diode switching dual 184A08 D103 104 203 204 303 304 403 404 503 504 603 604 703 704 803 804 906 Diode switching dual 184A07 D106 108 111 206 208 211 306 308 311 406 408 411 506 508 511 606 608 611 706 708 711 806 811 911 Diode switching dual 184A03 D112 113 212 213 312 313 412 413 512 513 612 613 712 713 812 813 LED surface mount 184A18 D912 913 918 919 Diode power 184A20 L101 104 201 204 301 304 401 404 501 504 601 604 701 704 801 804 901 904 Inductor 100 uH 162BN18K L102 103 202 203 302 303 402 403 502 503 602 603 702 703 802 803 902 903 907 908 909 911 Ferrite bead surface mount 162A12 JM905 Connector SMT top entry 170J10 Replacement Parts and Drawings 20 25A1041 RA 25A1041 RA Reference Designation Q102 109 111 112 114 117 202 209 211 212 214 217 302 309 311 312 314 317 402 409 411 412 414 417 502 509 511 512 514 517 602 609 611 612 614 617 702 709 711 712 714 717 802 809 811 812 814 817 924 928 929 931 Shure AMS8100 Automatic Microphone Mixer Shure Part Description Number Transistor 183A01 Q115 116 215 216 315 316 415 416 515 516 615 616 715 716 815 816 926 927 Transistor JFET N channel 183A22 Q901 908 910 911 915 918 Transistor Darlingt
11. It has a very fast attack time about 4 mS and relatively slow decay time 100 mS U911 an optoisolator performs the actual gain adjustment but the limiter circuit provides the dc control voltage neces sary for the optoisolator s action U907A U907B and associated components form a full wave peak rectifier with 6 dB of gain This rectified signal is fed to U907D and its surrounding components which is an inverting gain block with different gains set by the limiter DIP switch These different gains manifest them selves as different limiter thresholds When this amplified rectified sig nal s level reaches a certain level current will flow through D923 U911 s LED and R9186 This current flowing through U911 s LED causes U911 s resistor to drop in value which lowers the gain of U906B This current also generates a voltage across R9186 When this voltage goes below 15 mV U908C s output will clamp to 15 Vdc This turns off U908B which turns off Q928 This allows current to flow through the limiter LED segment on LED902 C959 R9169 and U908B act as a pulse stretcher to extend the on time of the limiter LED The output meter gives a visual indication to the ac voltage level at the line output connector The meter is a full wave peak responding type with a relatively slow decay The rectified output signal as provided by U907A and U907B is fed into U907C U907C is a half wave rectifier buffer When the signal a
12. This drops U802 pin 11 lower than U802 pin 10 2 5 Vdc causing U802D s output to clamp to ground R8050 and C814 slow down this clamped signal so that it doesn t make a tick in the audio circuits When this signal goes low it does several things First it pulls U802 pin 8 low so that U802C cannot turn on disabling the OVERRIDE function Second it mutes the Link A audio by turning on Q807 which immediately kills any current going to U808 the optoisolator causing its resistance to go high Third U802A the main gating comparator and U803D the last mic lock on are disabled via Q810 and U805B respec tively The channel reacts to it as if it were off and another channel can turn on in case the muted channel was the only microphone that was on Fourth the Link B audio is muted accomplished via U807A and Q815 Q816 When the output of U802D goes low U807 pin 5 is pulled low caus ing U807A s output to go low This in turn pulls the gates of Q815 and Q816 to about 12 5 Vdc causing the junction field effects transistors 7 Characteristics Shure AMS8100 Automatic Microphone Mixer Mix Stage Characteristics JFETs to go high impedance between their source and drain pins Q817 C830 R8130 and R8135 again are for de ticking The OVERRIDE terminal for each channel works similarly to the MUTE until the output of U802C When this point pulls low current is pulled through D806 clamping the output of U803C to
13. c connector on the rear panel through its integrated power switch and through the fuse F901 F901 is a slow blow type fuse because the power supply pulls a large surge of current on start up to charge the filter caps T901 steps the line voltage down to 30 Vac with a center tap connected to ground For the 15 Vdc supply the main 2200 uF filter capacitor C954 is charged to approximately 20 Vdc through a standard full wave bridge comprised of D912 D913 D918 and D919 The 1000 pF capacitors across each diode reduce susceptibility to rf signals picked up through the ac power cord R9216 and R9218 provide current to the zener diode Z903 to establish a fixed 8 2 Vdc voltage Q932 s base is connected to Z903 via a resistance capacitance RC filter to reduce noise from Z903 Q932 s emitter follows the base voltage minus about 5 Vdc R9212 and R9213 force Q932 to pull current through Q919 Q921 Q922 and Q923 to turn them on These transistors then are biased through R9219 so that the big transistors collectors provide a stable 15 Vdc R9209 R9211 R9214 and R9217 help prevent current hogging between the big output transistors The 15 Vdc supply operates the same as the 15 Vdc supply but the polarities are reversed D915 and D922 provide reverse voltage protection to the transistors when the unit is turned on and off 2 25A1041 RA Shure AMS8100 Automatic Microphone Mixer Microphone Preamps Channel EQ
14. g the audio through the optoisolator a smooth fade out Last Mic Lock On Circuit U803D and its associated components comprise the last mic lock on circuit When a channel turns on U802A s output pulls D811 pin 3 to ground This creates two voltages at U803D pin 10 and pin 11 due to resistive dividers formed by R8076 R8075 R8084 R8083 and R8087 R8087 is in the master section and is connected via the Last Mic Lock On Bus Link F The voltages at U803D pin 10 and pin 11 for a chan nel when it is the only channel on are 7 5 Vdc and 6 0 Vdc respectively In this condition U803D pin 10 is higher than U803D pin 11 caus ing U803D s output to clamp to ground This locks the channel on even if U803C s output goes high impedance If two microphones are on at the same time the voltages at U803D pins 10 and 11 change to 5 0 Vdc and 6 0 Vdc respectively due to the loading of more resistors on Link E In this state U803D pin 10 is lower than U803D pin 11 and this causes the output of U803D to go high impedance At the instant that one of the microphones goes off the volt ages will go back to 7 5 Vdc and 6 0 Vdc clamping U803D on again and locking on the last channel More than two microphones behave in the same way that two micro phones do The more microphones that come on the lower the voltage at U803D pin 10 drops The last mic lock on circuit can be defeated by changing one of the DIP switches This grounds
15. ge Gain Controls at full clockwise Output Input Mic Aux Line Headphones Direct Out AMS26 mic 20 5 20 38 72 dB SPL in dB dB dB dBu Aux 4 29 44 52 dB dB dB dB Send Return 20 5 20 28 dB dB dB dB Inputs Impedance Designed for Actual Input Clipping Input use with typical Level Mic AMS Mics only 400 kQ 132 dB SPL Aux lt 2 Q 10 KQ 24 dBu Send Return lt 2 Q 100 kQ 20 dBu Outputs Impedance Designed for Actual Output Clipping Output use with typical Level Line gt 600 Q 60 kQ 24 dBu Headphones 8 200 Q 1 KQ 6 dBu 60Q recommended Direct Out gt 2Q 1kQ 18 dBu Send Return gt 2Q 1kQ 18 dBu Service Procedures 14 25A1041 RA 25A1041 RA Shure AMS8100 Automatic Microphone Mixer Total Harmonic Distortion lt 0 1 at 18 dBu output level 80 Hz to 20 kHz through 80 Hz 20 kHz filter Input 1 and Master at 5 all other controls at full counterclockwise Hum and Noise Equivalent Input Noise 27 dBu A weighted Output Hum and Noise through 20 Hz to 20 kHz filter channel controls full counterclockwise Master full counterclockwise 90 dBu Master full clockwise 65 dBu Polarity Mic Line send inputs to all outputs are non inverting Aux input to all outputs is inverting Input Channel Activation Attack time 4 msec Hold time 0 4 sec switchable to 1 0 sec Decay time 0 5 sec Off Attenuation 15 dB switchable to Overload and Short
16. have a ripple on it If this voltage is not there there may be a short in subsequent circuitry the diodes feeding these capacitors may be open or the capacitors themselves may be shorted YX Check for 8 2 Vdc across Z903 and Z902 If not there the zener diodes may be shorted i Check for 7 7 Vdc at Q932 s emitter and 7 7 Vdc at Q924 s emitter If not there Q932 or Q924 may be bad Y Check for about 1 2 Vdc across the base emitter of Q919 and Q915 If not there Q919 may be bad Channel EQ Apply a signal to the mic line input Check for the signal at U801 pin 1 Check for the signal on the other side of C834 Check for the signal at U809 pin 7 YY RN 25A1041 RA 17 Bench Checks Shure AMS8100 Automatic Microphone Mixer Notes This page intentionally left blank Noles 18 25A1041 RA Shure AMS8100 Automatic Microphone Mixer Replacement Parts and Drawings Parts Designations 25A1041 RA The following comments apply to the parts list and the schematic The first number of the reference designator refers to its channel number For example R1027 refers to a channel 1 resistor X7216 refers to a channel 7 jumper and so forth Reference designators for the master section are preceded by the number 9 such as T901 X901 and so forth Resistors All resistors are surface mount with 1 49 W rating and 1 tolerance Capacitors Unless otherwise noted non polarized capacitors are surface mount
17. ing Protection Shorting outputs even for prolonged periods causes no damage Micro phone inputs are not damaged by signals up to 3 V Line and monitor inputs are not damaged by signals up to 20 V Equalization Low frequency 6 dB octave cut adjustable corner from 50 Hz to 300 Hz High frequency 6 dB at 5 kHz 8 dB at 10 kHz shelving Limiter Type Peak Threshold Switchable off 4 8 16 dBu at output Attack time 2 msec Recovery time 300 msec Indicator Lights red when limiting occurs Input LEDs Green on channel activation red at 6 dB below clipping 15 Service Procedures Shure AMS8100 Automatic Microphone Mixer Notes This page intentionally left blank Noles 16 25A1041 RA Shure AMS8100 Automatic Microphone Mixer Bench Checks Power Supply General i Check to see if F901 is not blown If it is blown check the unit to see why it blew If nothing can be seen replace F901 and slowly bring the ac power up with a Variac while monitoring the supply rails If any of the supplies appear shorted remove pow er and do more troubleshooting of the circuitry Check for about 40 Vp p at the secondary of T901 The signal should look like a sine wave with flattened peaks If it is not there suspect T901 SW903 F901 the wires to the ac power connector the ac power connector or the printed circuit board 15 Vdc Supply Check for about 20 Vdc across C954 and across C953 This signal will
18. io is not gated and the impedance and level of this bus are lower Link A Local and Link B Local perform identically to the normal Link A and B except that this bus is not connected to the link jacks and thus is not linked to other mixers When mixers are linked the Global Local DIP switch selects which of these mix stages connects to the output stage U905 performs this switching When the Off Attenuation switch is set to minus infinity Link B is switched out of the audio This switching is done by U902C and U905C 8 25A1041 RA Shure AMS8100 Automatic Microphone Mixer Master Gain Stage and Output Limiter Output Meter 25A1041 RA The master gain stage is U906B and its associated components The master gain stage is an inverting gain stage The output stage is U901 and its associated components The SSM 2142 chip is an active balanced line driver The ac output voltage seen across U901 pin 3 and pin 14 is 6 dB higher than the input voltage at pin 6 If either the positive or negative pin at the output is grounded the output across U901 pins 3 and 14 will stay the same C910 and C911 protect the chip from phantom power C901 C902 L901 L903 L903 and L904 are for rf filtering The limiter circuit prevents the output stage from clipping and keeps the maximum peak output level below a certain level set by the user The limiter is a high quality full wave peak limiter with a high limiting ratio
19. ion for 120 V operation Locate fuse F901 and remove it Replace fuse F901 with a 100 mA 250 V time delay fuse for 230 V operation or a 200 mA 250 V slow blow fuse for 120 V operation If changing to 230 V operation replace the power cord with a cord rated for 230 V operation an IEC appliance connector on the equipment end and a CEE 7 7 Schuko mains connector on the other end If changing to 120 V operation replace the power cord with a cord rated for 120 V operation an IEC appliance connector on the equipment end and a mains connector suitable for 120 V operation on the other end For systems that require other mains connectors obtain a power cord with an IEC 320 type mating connector for connection to the unit and an appropriate plug on the other end for connection to the mains 25A1041 RA 13 Service Procedures Shure AMS8100 Automatic Microphone Mixer Product Specifications After all tests are completed the unit should perform to the following specifications Measurement Conditions unless otherwise specified Line voltage 120 Vac 60 Hz 230 Vac 50 Hz Full gain 1 kHz one channel activated Source impedances Mic 150 Q Line 150 Q Terminations Line 10 KQ Phones 300 Q tip sleeve and ring sleeve Direct Out 10 kQ Auto mode Equalization controls adjusted for flat response Frequency Response Ref 1 kHz channel controls centered 80 Hz to 20 kHz 2 dB 3 dB corner at 25 Hz Volta
20. nnel s microphone on or off Directional Intellimix has three main sections 1 Direction Sensitive AMS Microphones 2 Maxbus 3 Last Mic Lock On Circuit These sections work together to decide whether the channel s microphone should be turned on or off To turn a microphone on U808 a Light Dependent Resistor LDR or optoisolator goes from high resistance gt 1 MQ to low resistance lt 1 KQ This connects the audio from U801 pin 7 to the main mixing bus Link A and sends audio to the output To turn a microphone off U808 s resistance goes high so that no audio is passed through it However listening to the output of the mixer as normally set up the microphone will still be heard when it goes off because of the off attenuation circuit Instead of turning a microphone completely off it sounds better to turn it down to only 15 dB from its on level This is done through the Link B mixing bus The audio signal on this bus is not turned on or off by the Directional Intellimix circuitry Direction Sensitive AMS Microphones The heart of the Directional Intellimix circuitry is the direction sensitive microphones Each of these microphones contains two back to back cardioid microphone capsules Each of these capsule s signals is sent separately to the AMS8100 mixer via a three conductor micro phone cable These microphones in conjunction with the microphone ratio circuitry determine if someone is speaking
21. on NPN 183A24 Q912 913 919 921 923 Transistor Darlington PNP 183A34 U101 201 301 401 501 601 701 801 Dual Op Amp 188A58 U102 103 107 112 202 203 207 212 302 303 307 312 402 403 407 412 502 503 507 512 602 603 607 612 702 703 707 712 802 803 807 812 903 904 906 913 Dual Op Amp 188A18 U104 105 110 204 205 210 304 305 310 404 405 410 504 505 510 604 605 610 704 705 710 804 805 810 908 909 912 Quad Comparator 188A123 U106 206 306 406 506 606 706 806 Transistor Array 188A263 U108 208 308 408 508 608 708 808 902 905 Analog switch 3X SPDT 188A05 U109 209 309 409 509 609 709 809 907 Quad Op Amp 188A260 U111 211 311 411 511 611 711 811 911 Optoisolator 86A8969 U901 Balanced Line Driver IC 188A143 21 Replacement Parts and Drawings Shure AMS8100 Automatic Microphone Mixer Reference Shure Part Designation Description Number VR102 202 302 402 502 602 702 Potentiometer Blue Shaft 802 50k 20 46A8060 VR103 203 303 403 503 603 703 803 901 903 Potentiometer 100k 20 46A8003 VR104 204 304 HE AA Potentiometer Black Shaft 804 100k 20 46B8060 22 25A1041 RA Replacement Parts and Drawings
22. signal is not the highest then that diode will be reverse biased U803B checks to see if the diode is conducting If it is conducting then the Maxbus criterion has been met and U803B pin 1 goes high If the output of U803B and U803A goes high the channel will gate on Last Mic Lock On The Last Mic Lock On circuit keeps the last microphone that was activated turned on The first sub block that feeds all of the circuits is the full wave rectifier circuit comprised of U106 and its associated components C824 C827 C828 C829 R8115 R8116 and R8117 form a filter circuit that only passes mid band frequencies On positive half cycles U806 pin 2 causes pin 1 to go low which turns on Q808 This directs all of the cur rent flowing through R8106 down through Q808 and into C823 On the negative half cycles Q808 is turned off and no current flows through it The negative half cycles are inverted by U806D and then rectified in the same way as above by U806B C823 R8107 and R8108 form a filter for the rectified signal U806C buffers this rectified signal for subsequent circuitry Hold Time Circuit When a channel is allowed to turn on U803C pin 8 goes higher than U803C pin 9 This pulls the output of U803C low immediately discharging C819 This in turn brings U802A pin 5 lower than U802A pin 4 causing the output of U802A to go low ground This causes the transistors to turn the optoisolator on thus turning the channel on Af
23. t U907 pin 12 is higher than the voltage across C948 then U907 pin 14 swings higher causing current to flow through D917 and R9173 thus charging C948 When the voltage at pin 12 is lower the C948 C948 is discharged through R9173 R9174 R9175 and D917 The output of U907C sinks this current 9 Characteristics Shure AMS8100 Automatic Microphone Mixer The voltage across C948 is fed to the string of comparators U908 U909 and U912 When the outputs of these comparators are low 15V the individual LEDs of LED902 are off Q929 Q931 R9189 and R9191 form a current source This current is consumed by the comparator outputs until they go high impedance one by one This allows this current to flow through the LED segments one by one Mixer Link Circuitry Characteristics The link circuit allows two or more mixers to be interconnected When two mixers are linked Link Out to Link In several busses get tied together directly Link A Link B Link D Maxbus Link E Reverb Inhibit Link F Last Mic Lock On and Aux In Bus In all but one mixer of a linked system certain elements must be switched out to maintain proper bus impedances R9087 Link F bus R9125 R9126 Link A bus and R9141 R9142 Link B bus Pin 2 of the link connectors is the link sense pin When pin 2 of the Link Out jack is grounded mixers are linked Q925 is turned on This pulls the gates of Q926 and Q927 low 14 Vdc which makes these
24. ter the channel is on and the decision is made to turn it off the output of U803C changes to high impedance U802A pin 5 does not immediately go high however C819 gets charged up via R8062 and R8061 The channel will go off after the voltage across C819 reaches the level at U802 pin 4 hold time bus This is typically about 0 4 5 Characteristics Shure AMS8100 Automatic Microphone Mixer Characteristics seconds This time is changed by changing the DIP switch setting to 1 0 seconds which raises the voltage at U802 pin 4 Optoisolator Turn On Circuit When U802A s output is pulled to ground to turn the circuit on C818 and C817 are immediately discharged This pulls current through R1063 and R8064 which pulls their current through the base emitter junction of Q806 Q806 and Q805 are connected as a current mirror so that Q805 turns on along with Q806 and sends a proportionally higher current through U808 s LED The current through U808 makes its internal resistors go to a low resistance letting the audio pass The current through U808 s LED also passes through R8057 providing a voltage for the logic circuitry that a channel is on When the channel turns off the output of U802A goes to high impedance and allows C817 and C818 to be slowly charged up by R8064 and R8063 respectively This tapers the current down smoothly through the base emitter junction of Q806 in turn tapering the current through the optoisolator and givin
25. witch 4 High Frequency Shelving Filter 1 8 14 LINK IN LINK OUT Jacks 5 AUX Level Control 15 OUTPUT Removable Block Connector 6 Aux INPUT Jack 7 MASTER Level Control 16 Output Level Switch behind connector 8 Output Level Meter 17 AUX D O D O Slide Switch behind connector 9 PHONES Control and Phone Jack 18 Input Removable Block Connectors 1 8 10 Power On LED 19 DIRECT OUT Phone Jacks Figure 1 AMS8100 Controls and Connectors Service Note Shure recommends that all service procedures be performed by a Factory Authorized Service Center or that the product be returned directly to Shure Brothers Inc 1998 Shure Brothers Inc Printed in U S A 25A1041 RA Shure AMS8100 Automatic Microphone Mixer Circuit Description Power Supply Replacement Parts and Drawings For individual channels the first number of the reference designator refers to its channel number For example R1027 refers to a channel 1 resistor X7216 refers to a channel 7 jumper and so forth Reference designators for the master section are preceded by the number 9 T901 X901 and so forth Because the channels are identical the channel 8 circuit is used when individual channel circuitry is discussed The AMS8100 power supply is a linear supply using discrete transis tors for regulation It converts varying line voltage into well regulated multiple voltages 15 15 for the circuitry to use Power is supplied to T901 via the a
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