2600 Service Manual
Contents
1. 1 7 2207 zw 1 208 NS 5 he 1 z0 L 1 SAMS Ni Sarwa Tow i 8 zon RL 5 EM Y 2 522 foe E BS 189 se2 85 592 1 Is 6928 wo 165 Lr NN 01 24 983138 22271 1879 5828 we een rao 5 AW 907014 953532 YIN 9 2 3 ODEL 2600 2 SCHEMATIC 2 of 2 BOARD4 amp 4 483 0481 007 wes es FROM LEFT AND RIGHT gt PAEAPPLIFIERS SPEAKER VoL FOR MONITER SPEAKERS OF 83252. 5 Sond adi GH 9H Z 9601 MY esiwueuio ss lun L 8310 277 907705 ANI gt oe 2 2202 a 10 52 57 Vs 0222 x zoo zoo 7 1901 e gt ANF A1ddNS 0 L 1207 E viov GOW 1 2 081908 L 0808 1 8 9 0 0 01 98 WVYOVIG 8 0092 0 non Jonuoo puroq ay O4 Tien ore I IIIIIIYIIIIII II 8 3 o k 9 ovr non 7 1 Raise 1 slider into the filter and close initial and fine tune sliders 2 Raise the ADSR control slider 3 Select ADSR settings so that a sharp envelope occurs when a key is depressed 4 Listen to the output of the filter through the Monitor speakers while depressing each ke
3. 15 VOLTS OUT TRIGGER OUTPUT 4 6 106 SMC 002 SERVICE MANUAL CORRECTION Bd 4A AR ADSR VCA ca aa 23 48 AR our pur 4020 ADSR A EXPONENTIAL GAIN e nos rs ea 7 Rio Voor pecca ay Fe 4019 LINEAR GAIN a AOU Pur MIER TUF 998 VOLTAGE CONTROLLED AMPLIFIER 2 12 3 mm ADJUST LINEAR GAIN FOR THE o o AMPLITUDE ON THE OUTPUT AS eT ON THE VCA INPUT WHILE HOLDING L THE MANUAL START BUTTON YOUAGE CONTROLLED MPO AS OUTPUT OF VCO 1 AR OUTPUT DEPRESS MANUAL START INVERTED OUTPUT CHANG 2 JX p n Aw d MODEL 2600 DATE 10 29 74 _ SUBJECT 2600 SERVICE MANUAL CORRECTIONS PAGE 1015 THE FOLLOWING CORRECTIONS SHOULD BE MADE TO YOUR 2600 SERVICE MANUAL PAGE 43 Linear input to the VCA should be shown with the input slider fully UP on steps 8 through 10 PAGE 98 33 amp 37 10K resistor should be shown from pin 2 of 20 AR circuit and A1 ADSR circuit to ground PAGE 106 The keyboard connecting cable pin connections should be shown the p
4. rise and fall times It is used primarily to control the VCA and the VCF When the ADSR is supplied with a gate and a trigger from either the keyboard internal clock or the manual start button the voltage first rises to 10 volts Attack and then de creases to a predetermined level Decay and remains there Sustain while the gate signal is present Finally the voltage decreases to zero Release when the gate is removed The attack time initial decay sustain level and the final release are each controlled by the four sliders on the front panel 02 4020 board is turned off unless there is a gate signal present on pin 2 of the 4020 board In the off state 02 5 collector voltage is high which holds on 07 the trigger enable As long as 07 is on all trigger signals entering on pin 1 of the 4020 board are grounded out which prevents the ADSR from initiat ing an attack when no gate is present When a key or the manual start button is depressed the gate signal turns on 02 through 01 The voltage on the collector of Q2 drops to 15 volts turns off and O7 turns off which allows the trigger signal to enter through C4 and R20 The keyboard trigger which is delayed by the keyboard electronics arrives on the base of 08 4020 board 15 milliseconds after the rise of the gate voltage The trigger turns on Q8 Which turns on O6 The collector of Q6 rises and latches Q8 and 06 on through 688 The voltage on the collec
5. f EY 24 22 8159 150K 8 4 856 M 8 90 8 LEE R151 100K E38 2 100K Loc E R152 100K not encapsulated In order to use the newer style filter in an older unit modifications are required to the control input as shown on the circuit below The newer 4072 module is identical in operation to the 4012 GS VCF Output 3 6 2 CONTROL REJECTION Ref Trimmer Specifications Trim Procedure R193 Control 1 Repeat steps 1 3 for Linear Gain Adjustment Rejection 2 Patch VCO 2 LF sine wave 2Hz into VCA AR Control Input jack 3 Close VCF Audio Input slider 4 Adjust R193 for minimum output offset R194 High Frequency NO ADJUSTMENT NECESSARY Reject R195 Exponential Gain 1 Set R195 full clockwise position 3 7 Board 5 1 Adjustments Sample and Hold 3 7 1 INTERNAL CLOCK not accessible to front panel R385 Pulse Width 1 Monitor Internal Clock output with an oscilloscope 2 PutS H rate slider at maximum 3 Adjust R385 for 50 duty cycle SECTION 4 ASSEMBLY amp DISASSEMBLY 4 1 Opening the 2600 Console 3 Using two dummy plugs in jacks as handles on the lower portion of the panel lift the 1 Remove the three screws on each side of the panel up and then out from the bottom front panel Take care
6. Models 2600 2606 SERVICE MANUAL Kybd Model 3620 technical information is covered separately in the 3620 Kybd Service Manual Document Number 90004 CONTENTS SECTION 1 General SECTION 2 Circuit Descriptions SECTION 3 Calibrations 7 SECTION 4 Assembly amp Disassembly 11 SECTION 5 Revisions Changes 12 SECTION 6 Miscellaneous Notes 13 SECTION 7 Diagrams Schematics amp Assemblies 16 SECTION 8 Parts List 32 THE INFORMATION CONTAINED HEREIN IS CONFIDENTIAL AND PROPRIETARY TO ARP INSTRUMENTS INC IT IS DISCLOSED TO YOU SOLEY FOR PURPOSES OF INSTRUCTION AS TO OPERATION OF THE EQUIPMENT AND MAINTENANCE AS APPROPRIATE IT IS NOT TO BE USED BY YOU FOR ANY OTHER PURPOSE NOR IS IT TO BE DISCLOSED TO OTHERS WITHOUT THE EXPRESS PERMISSION OF ARP INSTRUMENTS INC ARP INSTRUMENTS INC 45 Hartwell Avenue Lexington 02173 617 861 6000 Document Number 90021 New Edition September 1977 1977 ARP Instruments Inc tuning procedure for the new module and use the oscillators use the new oscillator as the tuning 4017 4027 tuning procedure for the remaining standard once it has been tuned 3 25 VOLTS PER OCTAVE ADJUSTMENT PROCEDURE Ref No Trimmer Specifications Trim Procedure R60 1 Monitor VCO 1 output sawtooth or square with frequency V OCT counter or other tuning standard Depress low C and adjust frequency for 100Hz using coarse and fine tune sliders Depress high
7. 22 erbi 2 1 L RIY NA 3 SAMPLE AND HOLD 54 Bd 5 Bd MODEL 2600 SCHEMATIC BOARDS5 amp 5 1 MODEL 2600 ASSEMBLY BOARD 4 2 1 8 8 N 5 3604 1070 83921111 gt 391 104807 x 486100 0 Sa Aun 3705 79 210 0 100 34 9 6 ASL We 2 1 es ola als ANDONI 7 Jey 11 1401401 7480 01 3 1301201 2 4248 PNP 02 1301701 2 5172 TSTR NPN BR1 1201001 MD920A BRIDGE RECTIFIER 04 1304501 1100 TSTR POWER 05 1304301 MJE1090 TSTR PNP POWER C6 7 1100612 G 0 010 G 20 0 CAP 10uf 35V TANT 1 2 1101301 TCW102V050N1R3P CAP 1000uf 50V DC 3604P Keyboard REFERENCE ARPPARTNUMBER ARP MFG NUMBER DESCRIPTION 1 7205501 HIGH 2 OP MODULE 2 1100311 15uf POLY CARB C4 5 1100609 108 C6 1100317 1uf C7 1100315 CAP 47uf 50V CR1 1200301 1N4148 DIODE 02 3 5 1301701 2N5172 TST
8. Riad ay 80 ya n NOSE 519573 Re 895 4 1 GAIN v A NOTES look RSS 250 1 UNLESS OTHERWISE SPECIFIED ALL RESISTOR VALUES ARE IN OHMS we ALL CAPACITOR VALUES ARE IN uf T ev 0 154 P PICOFARADS 2 HIGHEST REF DES C62 E43 2164 3 CONVENTIONS USED FoR SUPPLY NOLTAGE CONNECTIONS Riss wees 100K Vlo IMPLIES 5 M 6 47 Li woe JACKS ON PANEL 5 MODEL 2600 ALL SLIDE POTENTIOMETERS SCHEMATIC BASE VIEW BOARD 3 me Gy lt gt 3 e gt o TE 2 1 2 auvoa 05 0092 0 EW INM ANIS 7l est 105 24 w KREISE I gt as T s 9913539 3 22 Nus ey vo 208100 azz ELI fasa ama 78 7 gt gt z 9 5 1 1 L 1207 09A 6002 8 ew 0092 0 ls
9. 9 e NIT 3001 gt 6656266599090 B 51151 15 5 4 3001 Esp U 1 OOOOOOOOOOOOO OOOOOOOOOOOOO TE OOOOOOOOOOOOG 2 2 5 819 8 8 8 222 x gt gt gt gt 2 s c 5 8 5 5 2 518 ales 5 m z 9 15 3001 3001 OA IO 9001 3001 NIT 3001 gt gt NIT 5 112 115 NIT 3001 NIT 3001 NIT SUF 05 gt m CN hod How z L 98 98 SN 011 ERVICE NOTES ERVICE NOT MODEL 2600 1031 74 SUBJECT NOTICE OF PRODUCTION CHANGE PAGE 1 of 2 After October 1 1974 all normalizing jacks the 2600 have been replaced with a panel mounted jack Jumper wires connect the new jack to the printed circuit board See page 2 for the locations of the affected jacks Use
10. SECTION 7 PARTS LIST 1 PART NUMBER ARP MFG NUMBER DESCRIPTION 21 2 3 4 1400801 LM301AN IC OP AMP M1 4014 7204901 RING MODULATOR CR1 2 1200301 1N4148 DIODE 51 1901601 6 1281 SWITCH R23 1000811 JAIN200P104AA 100K AUD ROT POT R2 29 31 1001201 WH3259 SLIDE POT 100K LIN E1 5 6 2101601 42A TINI D JACK E2 3 4 7 2101201 142A TINI D JACK CASE R33 34 1000913 U201R503B TRIMPOT 50K LIN R35 1000917 U201R254B TRIMPOT 250K LIN C7 22 23 1100609 G 0 001 G 20 0 1uf 35V C13 14 18 19 20 21 1100605 G 0 010 G 20 0 CAP 10uf 25V Board 2 REFERENCE ARP PART NUMBER ARP MFG NUMBER DESCRIPTION 2 3 4027 1 720000 Ref 34 1001201 WH3259 SLIDE POT 100K LIN Ref to pg 34 1001202 WH3260 SLIDE POT 100K AUD 18 52 68 87 1000915 U201R1048 TRIMPOT 100K LIN R60 78 97 1000911 U201R253B TRIMPOT 25K LIN 54 5 6 1901501 6 6 SWITCH 15 18 22 26 29 32 2101601 42 TINI JACK E13 14 19 20 21 2101201 142A TINI JACK CASE 27 28 28 9 1400801 LM301AN M IC OP C34 39 1100609 G 0 001 G 20 0 CAP 1 35V CR7 9 1200301 1N4148 DIODE Board 2 1 REFERENCE ARP PART NUMBER NUMBER DESCRIPTION A14 15 16 17 1400701 LM301AH IC OP 01 1304701 2581 TSTR PNP 02 1301701 2 5172 1303901 958 CHAN CR14 1200301 1N4148 DIODE R115 12
11. modifier Although many functions on the 2600 can be used as both controllers or signal sources the following table suggests the most common use of each function on the 2600 SOURCES MODIFIERS CONTROLLERS vco1 ADSR vco2 VCA AR RING KEYBOARD MODULATOR NOISE ENVELOPE GENERATOR ELECTRONIC FOLLOWER SWITCH SAMPLE REVERB AND HOLD INVERTERS VCO s IN LF RANGE LAG PROCESSOR INTERNAL CLOCK MICROPHONE PREAMP SECTION 2 CIRCUIT DESCRIPTION This section is to be used as an aid in circuit analisis Some trouble shooting hints are provided for certain boards in Section 6 page 13 2 1 Power Supply Voltage Source a full wave bridge rectifier supplies about 30V plus and minus to the regulating circuitry C1 and C2 filter out ripple on the supply lines 15 Volt Supply A1 contains a voltage reference which supplies about 7 0 volts to pin 6 of A1 This fixed voltage is connected through pin 5 to the non inverting input of a comparator The output of the comparator is connected to an emitter follower also located inside A1 which controls 04 the current amplifier The power supply normally delivers 15 volts to the output if the voltage should change the voltage at the junction of R7 and R9 will also change The resistor junction is connected to the inverting input of the comparator through pin 4 of A1 If the voltage at this point should drop the output of the comparator
12. C and adjust R60 trimmer VCO 1V OCT for 1600Hz Repeat steps 1 and 2 until low and high C are correct R78 VCO 2 Repeat same procedure as indicated VCO 1 using VCO 2 R78 trimmer Note If VCO 1 V OCT adjustment has been accurately made then VCO 2 can be adjusted audibly by comparing its pitch to VCO 1 R97 3 Repeat indicated for 1 and 2 using 7 3 trimmer 33 Board 1 Adjustments 3 31 RING MODULATOR R33 R34 R35 Positive Null Put audio d c switch to d c position Raise VCO 2 slider into the Ring Modulator only Monitor Ring Modulator output with oscilloscope and adjust R33 middle trimmer for minimum output should be less than 10mv Negative Null Put audio d c switch to audio position and adjust R34 lower trimmer for minimum output should be less than 10mv Gain Raise both sliders into Ring Modulator and select audio d c switch to d c Adjust R35 for 20V P P maximum 3 4 Board 2 Adjustments 3 4 1 VCO 1 PULSE WIDTH ADJUST R18 Pulse Width Monitor VCO 1 square wave output with an oscilloscope and adjust R18 for exactly 5096 duty cycle square wave Located below VCO 1 Fine Frequency Slider power amp output through R344 The positive portion of the wave on the output of A40 controls the current through O30 and the negative portion of the signal passes through C
13. an oscilloscope Patch VCO 3 sawtooth to Audio Input jack and raise audio input slider fully Put the initial gain slider fully left minimum Raise VCA AR control slider all the way Depress and hold the manual start button and adjust R196 for 10V P P maximum signal output 50 1 FEE 106 8 49 Eh BOARD 4 i TES 4 ARR l T MODEL 2600 5 1 of 2 asav ozor K 2 38 MI AQ MODEL 2600 ASSEMBLY BOARD 3 mis LOOKING TOWARD TERMINALS 100K 5 i8 UR RI40 ALD l RING Ru RIGO lock DA 2 RESONANCE E43 50 197 OUTPUT 2 5 3 8 42 100K AUD RS MI 7205301 1 lt ceo T38 a 4012 ho 2143 look asv AUD c RBZ 3 R64 5 is iSv os 14 w ERE n X Riez ioox dis
14. is an input jack on another board 6 1 2 SAMPLE FAILURES No Module Output 1 Insure Power Supply plus and minus is getting to module 2 Be sure that output of module is not being affected externally 3 Check for good connection at module pins 4 Check for appropriate signal input at pins 5 Check to see that all control voltages are present and correct at the module pins NOTE When reassembling the unit install the top of the panel first then the bottom Lay the unit on its back to reinstall the screws Be careful when putting in the panel screws that the T nuts in the console are not crossthreaded 4 2 Opening the 3604 Keyboard TURN THE UNIT OFF BEFORE DISCONNECTING THE KEYBOARD CONNECTING CABLE KEYBOARD ELECTRONICS ACCESS 1 If repairs involve only the keyboard elec tronics remove the grey metal panel see illustration For proper operation of the keyboard be sure that this panel does not become grounded since it is at the Keyboard Control Voltage potential 2 If the keyboard contacts must be serviced remove the four screws on the keyboard case and remove the entire assembly KEYBOARD CONTACTS ACCESS SECTION 5 REVISIONS CHANGES 5 1 Types of Voltage Controlled Filter Modules 4012 4072 The later model 2601 s use a 4072 filter module This module is physically larger than the 4012 and is vum 232 E E um Po 0
15. manually by moving the initial frequency sliders or by control voltages from the keyboard other oscillators envelope generators sawtooth wave is converted to other wave shapes such as square pulse and sine waves When the range switch of the oscillator is in the lower position LF KYBD OFF the oscillator produces sub audio frequencies which are useful as control signals SECTION 1 GENERAL 1 1 Prewired Patches The 26005 prewired patches provide the most popular synthesizer effects without the use of patch cords by using the closed circuit tip and shunt of mini jacks This internally prewired patch may be overridden however by inserting a patch cord into the appropriate panel jack Note that a circle in the block diagram indicates a mini jack 1 2 Synthesizers in General Synthesizers include three types of circuits 1 signal sources 2 signal modifiers and 3 controllers In general sounds are produced by a synthesizer in the following manner SIGNAL SIGNAL RUIT SOURCES MODIFIERS CONTROLLER CONTROLLER A raw signal is produced by a signal source such as an oscillator or noise generator The tone or color of the raw signal is then shaped as the signal passes through the modifier which in the 2600 could be the ring modulator VCF or VCA Controllers are used to give automatic variations in the pitch of the signal source and or the operating characteristics of the
16. will rise turning on the emitter follower and the pass transistor thus raising the output voltage Similarly if the voltage at the resistor junction should increase the comparator will initially limit the current through the pass transistor and lower the output voltage R10 the 15 volt trimmer initially sets the voltage level on the output of the supply 15 Volt Current Limiting When enough current flows out of the positive power supply to cause a 7 volt drop across R6 the transistor connected to pins 2 and 3 of 1 turns on effectively shorting the base of the emitter follower to the output voltage of the 15 supply 04 in turn supplies less current to the output 3 4 2 FREQUENCY CALIBRATE Ref No Trimmer Specifications Trim Procedure R52 Frequency 1 Monitor VCO 1 output with an oscilloscope or frequency counter Calibrate VCO 112 FM sliders down 3 Remove Keyboard CV from VCO 1 or use dummy plug in VCO 1 CV jack 4 course frequency slider far right maximum 5 Put fine tune slider mid range 6 Adjust R52 for 8 33KHz R68 Frequency Monitor VCO 2 output with an oscilloscope or frequency counter Calibrate VCO 2 2 Repeat same procedure as described for VCO 1 calibrate using R68 R87 Frequency 1 Monitor VCO 3 output with an oscilloscope or frequency counter Calibrate 3 2 Repeat same procedure as described for VCO 1 calibrate using R87 3 43 2 B
17. 201 The signals then pass through R202 and R203 into the inverting input pin 2 of A25 on the 4 2 board The signal then goes to the pan slider and to the reverberator input jack At the pan slider the signal splits into two channels left and right When the pan slider is moved from left to right the arm of the slider grounds our right channel and then the left thus producing a pan effect The right signal passes through R256 into the inverting input pin 2 of A27 27 buffers and amplifies the signal and delivers it to the right outpt jack and also to the right power amplifier for the right internal speaker In the same manner the left channel signal leaves the pan slider through R255 and enters the inverting input jack and to the left power amplifier for the left internal speaker 2 5 5 REVERB BOARD 4 2 The Reverb circuit has one input that is prewired to the Mixer output The Reverb circuit also has two outputs the left is wired directly to the left preamp lifier and the right output is wired through the reverb output jack to the right preamplifier A signal entering the reverb circuit through the reverb input jack is AC coupled by C89 and enters the inverting input pin 2 of A28 on board 4 2 through 8272 R273 From the output of A28 pin 6 the positive portion of the signal passes through CR41 and CR40 and is amplified and inverted by Q26 The negative portion of the signal is amplified and inverted by 027 The com
18. 2600 is processed through one of the inverters in the voltage processors on the 2600 Since the inverter outputs are low impedance the trigger from the keyboard is grounded out by the inverter Solution Add a blocking diode in a patch cord form the inverter output to the tirgger input of the 2600 DETAILS OF CHANGE Materials Required 1 1 4148 DIODE 1 PATCH CORD Procedure 1 Cut open the patch cord and connect the diode in series with the hot lead 2 Mark the patch cord to identify anode 3 Insert the patch cord anode to inverter output and cathode to trigger input INVERTE Fo 7 ARP INSTRUMENTS INC 45 Hartweil Avenue Lexington 02173 617 261 5000 3604 KEYBOARD ELECTRONI COMPONENT LAYOUT E SERVICE MANUAL CORRECTION SMC 004 gs is sa CHANGE 18 10 FOIL SIDE VIEW 107 OL 2 SERVICE MANUAL CORRECTION SMC 003 3604P KEYBOARD ELECTRONIC OL FONVHO NOD Q8 VOSA 35 239971 50 vu 2 10 1327177 1 351 nsan aud em ee lt O gt 2 25 5 5 EEE o m Occo
19. 5 1000915 U201R104B TRIMPOT 100K LIN R121 128 1000909 U201R103B TRIMPOT 10K LIN Board 3 REFERENCE ARP PART NUMBER NUMBER DESCRIPTION M1 4012 7205301 1 4072 7213301 5 42 2101601 42 TINI D JACK E43 2101201 142A TINI JACK CASE R163 1000909 U201R103B TRIMPOT 10K LIN R162 164 1000915 920181048 100 LIN 5601 6 MODEL 0 ASSEMBLY POWER SUPPLY 060139 10 180 unsi 7 AGE gral 22 Nonno AGE gt 9 2108100 10908 001 3 79 39003309 LNIWLSNAV ATddNS YIMOd 01 NC 1 MODEL 2600 5 SUPPLY 211935 335 252 nose 600 1001 MODEL 2600 ASSEMBLY 3604P KEYBOARD SNOILV2O1 ANIVA 104 340115 0092 1 anv 9 2021001 3001 iz 1021001 HV3NI1 3001 H38WN 014913953 A14NnOWVv p4eoq 2074 0 10u uou 36 1 A I u E 0595500090600 7 5 q210000000000000 0000000000000 8 8181 18 9999000000000 C 0000060000000 wazisaninss oos 300
20. A LOCKED UP AT 4019 MODULE REPLACE THE BOARD 4 15 VOLTS SHORTED INTERNALLY 4019 MODULE VCA CLIPS NO PROBLEM LOWER RIGHT BOARD4 DISTORTS WHEN EXPONENTIAL INPUT CONTROL SLIDER PANEL ADSR IS USED FULLY SLIDER UP TOO FAR UP 6 2 Key Contact Adjustments for 3604P 3 Bus Note See Section 9 for 3620 Adjustment Procedure 6 2 1 CONTACT TIMING Ideally contacts should meet the bus exactly at the same time for the proper effect The control voltage change should occur at the same time as the leading edge of the gate so that the pitch changes at the same time as the ADSR is initiated which allows the signal to be passed by the VCA or VCF The trigger is delayed electronically 15 milliseconds to allow the noise on the leading part of the gate signal and the control voltage to subside f the trigger is delayed much more than 15 milliseconds the delay may become audible If some keys do not give the proper response or do not trigger the ADSR at all cleaning or adjustment may be needed 6 22 TIMING CHECKOUT PROCEDURE If any of the contacts fail to meet the bus rods at the proper time the following effects may result EFFECT Sound becomes audible before ADSR is initiated No sound at all ADSR is not initiated Pitch changes before previous envelope has com pleted Previous note is heard before correct note CAUSE Gate too soon or trigger too late Gate too late or trigger too soon Control Voltage t
21. C OP AMP 05 1302401 2 5460 TSTR CHAN 06 1301701 2 5172 TSTR GP S9 1900401 30 1 SPST MANUAL START 58 1901501 6 6 SWITCH 245 47 50 53 55 57 2101601 42 TINI P JACK E58 59 48 49 54 60 2101201 142 TINI D JACK CASE 61 62 63 64 65 R194 195 1000909 U201R103B TRIMPOT 10K LIN R193 196 1000915 U201R104B TRIMPOT 100K LIN Ref to pg 34 1001201 WH3259 SLIDE POT 100K LIN Ref to pg 34 1001202 WH3260 SLIDE POT 100K AUD Ref to pg 34 1001203 WH3261 SLIDE POT 1M AUD C62 63 64 65 1000609 G 0 001 G 20 0 1uf CR21 25 1200301 1N4148 DIODE Board 5 REFERENCE ARP PART NUMBER ARP MFG NUMBER DESCRIPTION E72 76 74 77 81 2101601 42 TINI JACK 84 70 71 73 75 78 79 2101201 142A TINI D JACK CASE 80 82 83 85 86 87 Ref to pg 34 1001201 WH3259 SLIDE POT 100K LIN Ref to pg 34 1001202 WH3260 SLIDE POT 100K AUD Ref to pg 34 1001203 WH3261 SLIDE POT 1M AUD Board 5 1 REFERENCE ARPPART NUMBER ARP MFG NUMBER DESCRIPTION C45 50 1200301 1N4148 DIODE A35 41 1400801 LM301AN OP 044 1302801 2 6076 PNP 045 1301601 2N4870 TSTR UNI JUNCTION 036 39 1301701 2 5172 TSTR 040 41 1301301 2 4392 5 N CHAN 4015 7205001 SAMPLE amp HOLD MODULE 4022 7204801 SSS NOISE MODULE C121 122 1100609 G 0 001 G 20 0 1 ELECT Power Supply REFERENCE ARP PART NUMBER ARP MFG NUMBER DESCRIPTION A1 1401301 723DC VOLTAGE REGULATOR
22. INTERV L CONTROL NOTE See section 3 of the 2600 SERV CE MANUAL if the voltage controlled oscillators are out of tune with each other across the keyboard ARP INSTRUMENTS INC 45 Hortwel Avenue Lexington 02173 817 261 6900 PAGE 2 of 2 SERVICE NOTE SN011 xoe ejas O
23. OARD 2 1 ADJUSTMENTS see pg 22 for pot location R115 Symmetry 1 Monitor VCO 2 triangle output with an oscilloscope Adjust 2 Adjust 115 for best triangle waveform R125 DC Offset 3 Adjust R125 so the peaks of the triangle waveform are not Adjust flat at either end R128 Gain Adjust 1 Monitor VCO 2 sine wave output with an oscilloscope 2 Adjust R128 for 10V output R121 Purity Adjust 3 Adjust R121 for the best sine waveform NOTE It may be necessary to readjust calibrations after performed in the order listed 3 5 Board 3 Adjustments Voltage Controlled Filter 3 5 1 FREQUENCY CALIBRATE R164 Frequency Calibrate Monitor VCF output with an oscilloscope or frequency counter Initial frequency slider left Fine tune slider mid range Resonance slider right All VCF input sliders down Disconnect keyboard or use dummy plug KYBD CV jack Adjust R164 for 10Hz output 2 25 955 25 ov yis SIO SPA 535 4 5 0092 13qOW 400100 x rex ENS FL ons gt 2 6 5 5 e PTL 252 206100 Yol a AS ev gt o 22 Xu 75 pre 2 2 xag CNV Ma E 2 OHJ O 6
24. R NPN 01 1302801 2 6076 TSTR PNP 04 6 1304701 2581 PNP VARIABLE INTERVAL 1000806 JAIN56S103UA ROT POT 10K FIXED INTERVAL 1000803 JAIN40S252UC ROT POT 2 5K PORTAMENTO 1000813 JAIN56S504UA ROT POT 500K TUNING 1000801 JAIN56S102UA ROT POT 1K 3620 Keyboard See Section 9 Miscellaneous ARP PART NUMBER ARP MFG NUMBER DESCRIPTION 2400801 O SHUKE HANDLE 2300405 6 32 x 1 SCREW HANDLE 2307301 6 32 x 4 ACORN NUT 2401001 X49 SLIDE POT KNOBS 1901701 POWER SWITCH 1800101 POWER LIGHT 2100601 POWER PLUG SOCKET 2201501 POWER CORD KYBD CONN CABLE 3604 2100901 CONSOLE JACK 2305902 NO 6 FIBRE WASHER 2101101 STEREO JACK 2307602 SHEET METAL SCREW HOLDER 2600601 SPEAKER 40ohm 2600701 REVERB TANK PARTS ORDERING phone Contact the ARP Service Department and Telephone 617 861 6000 Service Department Replacement parts can be ordered in writing or by use the ARP part number when ordering five accepted dollar minimum is required unless the order is received with cash in advance No collect calls will R153 1000903 U201R251B TRIMPOT 250ohm LIN R140 144 1001202 WH3260 SLIDE POT 100K AUD R146 147 1001201 WH3259 SLIDE POT 100K LIN C60 61 1100609 G 0 001 G 20 0 CAP 1uf 35V Board 4 REFERENCE PART NUMBER ARP MFG NUMBER DESCRIPTION VCA 4019 7205101 VCA ADSR 4020 7205201 ADSR 220 1400801 LM301AN I
25. R46 and CR45 to control the current through O32 The complete amplified signal is at the junction of R346 and R345 034 limits the current through the negative portion of the power amp Outputs A and B go directly to the 40 ohm speakers SECTION 3 CALIBRATIONS The following section includes all the calibrations in the 2600 3 1 Power Supply Adjustment NOTE THIS ADJUSTMENT MUST PERFORMED PRIOR TO MAKING ANY OTHER CALIBRATIONS 1 Connect a Digital Voltmeter across the plus 15 00 connection and ground red and black wire 2 Adjust R10 for exactly 15 00 3 Connect the DVM across the negative supply connection and ground black and violet 4 Adjust R13 for exactly 15 00VDC 3 2 2600 Tuning 32 1 VOLTS PER OCTAVE DEFINITION Tuning the 2600 requires the frequency of the oscillator to exactly double for each volt applied to the control input The Volts per Octave trim mer located above the calibrate trimmer adjusts the input of the oscillator for this response For example when an oscillator is tuned initially to 100Hz with low C depressed zero volts supplied to the oscillator the highest would produce 1600Hz four volts supplied to the oscillator VOLTS PER OCTAVE ADJUSTMENT FREQUENCY HZ 3200 VOLTS 3 2 2 TRACKING DEFINITION Oscillators which are tracking together will maintain the same relative frequency difference regardless of which key
26. able 231 1 VCO 1 generates sawtooth wave and a square wave The keyboard control voltage sample and hold ADSR and VCO 2 sine wave are prewired to the frequency control inputs of VCO 1 Pin 2 of the 4027 1 oscillator module is the control current summing point Current applied to this input controls the frequency of the oscillator Pin 5 is the sawtooth wave output of the module From this output the signal goes directly through to the sawtooth output jack through R106 and to the square wave converter through R47 Pin 18 allows an external capacitor to be connected to the oscillator so that it will operate at very low frequencies Pin 19 the calibrate input is internally connected to a trimmer R52 so that the normal frequency of the oscillator can be tuned When the range slide switch S4 is in the audio position the Keyboard Control Voltage is connected to the control summing input through R56 and the V OCT volts per octave trimmer R60 When the range slide switch is in the low frequency position one terminal of C40 is grounded adding capacitance from pin 18 to ground thereby lowering the operating frequency of the oscillator In addition the negative current is simultaneously allowed to enter the control input of the oscillator through R53 also lowering the frequency is the sawtooth to square wave converter a fixed voltage of about five volts is applied to the noninvert ing input of 8 pi
27. ct a Digital Voitmeter across the plus 15 00 connection and ground red and black wire 2 Adjust R10 for exactly 15 00VDC 3 Connect the DVM across the negative supply connection and ground black and violet 4 Adjust R13 for exactly 15 00VDC 22 Board 1 Preamplifier Envelope Follower Ring Modulator 22 1 PREAMPLIFIER The microphone preamplifier accepts any low to medium level external input A rotary control serves as an input attenuator and a three position slide switch selects one of three gain ranges X10 20db X100 40db and X1000 60db The preamplifier is useful with microphones electronic musical instruments and any other signals which do not have adequate signal level to drive the 2600 circuits directly The signal to be amplified enters the preamplifier circuit through R23 the gain control and is coupled through C24 to the noninverting input pin 3 of A4 The range switch S1 selects the feedback path for A4 through either R20 for X10 R20 and R26 for X100 or R20 R25 and R28 to ground for X1000 The amplified signal then passes from pin 6 of A4 through R27 to the output jack 2 2 2 ENVELOPE FOLLOWER The envelope follower generates a positive DC voltage output which is directly proportional to the amplitude of the audio input signal The envelope follower s sensitivity is such that a 2 volt peak to peak signal will produce about 5 volts DC on the output with the input slider fully up The preamplifie
28. e control voltage into the output of the VCA The high fre quency reject trimmer R194 is designed to minimize unwanted high frequency noise from the output of the VCA Often there is too little high frequency noise to warrant adjustment of this trimmer Pin 5 of the 4019 module is the audio output of the VCA 25 22 ATTACK RELEASE The Attack Release AR envelope generator produces control voltages with variable rise and fall times It is used primarily to control the VCA When the AR is supplied with a Gate signal from the manual start button keyboard or internal clock the output rises to 10 volts and stays at that level for the duration of the gate signal When the gate is no longer present the voltage decreases to zero The attack time and the release time are manually control lable by the sliders on the front panel The gate voltage passes through R172 CR25 and the attack slider R174 and charges C69 to 10 volts The charge time is determined by the position of the Attack Slider R174 At the same time the gate signal turns off Q5 through R214 so the C69 cannot discharge through it while the gate is present When the gate is no longer present O5 turns on and C69 discharges through O5 and the Release Slider R175 A20 follows the voltage level on C69 and buffers it from the output 2 5 3 ATTACK DECAY SUSTAIN RELEASE MODULE 4020 The Attack Decay Sustain Release ADSR envelope generator produces control voltages with vari
29. e frequency of the oscillators The O resonance is controlled manually by the resonance slider The resonance accentuates a narrow band of frequencies which produces a wow effect when the fc is varied When the Q is at maximum the VCF will oscillate producing a sine wave and can be used like the other voltage controlled oscillators The filter s five audio inputs are prewired to the Ring Modulator VCO 1 square wave VCO 2 pulse wave VCO 3 sawtooth wave and the noise generator Audio signals enter the VCF Circuitry through the five audio attenuators R140 through 8144 Pin 1 of the 4012 module is the audio input summing junction The output of the module is pin 5 The Resonance Slider R160 allows some of the output signal to feed back into the input through pin 2 R163 CONTROLS THE GAIN OF THE VCF and R162 eliminates the DC from the output The control voltages or signals enter the circuitry through the sliders R145 R147 Pin 3 and 11 are the control inputs R156 and R158 the Initial Frequency and Fine Tune Sliders add voltage to the control inputs to increase the fc R164 sets the fc when there are no external control signals R153 volts per octave sets the sensitivity of the VCF so that it will track with the other oscillators 25 Board 4 VCA AR ADSR Mixer Reverb Preamp 2 5 1 VOLTAGE CONTROLLED AMPLIFIER The VCA controls the amplitude of a signal passing through it When the initial gain slider on
30. ent only cost 350 Included with the modification is a porta mento interval footswitch and a one full year warranty Call the Factory for more details 4012 to 4072 Filter Conversion The 4012 to 4072 Filter conversion is available for all 2600 s See Section 5 page 12 for installa tion information 110 Volt to 220 Volt Conversion 1 Remove the 115 V wire from the terminal strip 2 Solder the 220 V wire to the terminal strip 3 Change the fuse to amp slow blow LINE CORD TO ON OFF SWITCH Power Supply loads down output is less than plus or minus 15V 1 Remove Power Supply connector from board one at a time to determine which board is at fault 2 After faulty P C board has been determined remove the Power Supply molex pins one at a time to determine whether the plus or the minus supply is at fault 3 Inspect closely for solder splashes or bridges 4 Locate active components on board and inspect for overheating 5 If unable to determine fault then it may be necessary to remove each of the sus pected active components one at a time SYMPTOM PROBLEM REPAIR LOCATION OUPUT OF VCF VCF OUTPUT OFFSET SEE SECTION 3 4 BOARD 3 AT 15 VOLTS INCORRECTLY SET VCF ADJUSTMENTS SIGNALS DISTORT NO PROBLEM VCF LOWER AUDIO INPUT BOARD 3 WHEN ALL THREE OVERDRIVEN SLIDERS TO UP OSCILLATORS ARE USED TOGETHER SYMPTOM PROBLEM REPAIR LOCATION VC
31. ft slider controls the noise color As the color slider is lowered from top to bottom the higher frequencies in the noise are attenuated The output from the Noise Generator is prewired to the VCF VCO 2 and VCO 3 and the Sample and Hold The source of the noise is an amplified reversed junction of a selected transistor Q1 on the 4022 module Z1 amplifies and clips the noise to 10 volts peak to peak A35 on board 5 1 filters out the higher frequencies of the noise signal leaving only a low frequency noise signal The noise color slider pans from the output of the low frequency noise filter A35 to the output of the 4022 pin 5 A36 amplifies and buffers the final noise signal 262 VOLTAGE PROCESSOR The top inverter has two attenuated inputs and two fixed inputs which are useful for mixing voltages or signals The gain from either of the attenuated inputs is adjustable from to 1 The fixed inputs are calibrated for a gain of 1 exactly The upper attenuated inputs of the inverter are prewired to 10 volts and will produce a 10 volts on the output when the slider is fully right The lower attenuated input is prewired to the Keyboard Control Voltage and will produce a negative complement of the Keyboard Control Voltage output when the slider is fully right The second inverter is the same as the upper inverter except that it has one attenuated input and one fixed input The attenuated input is prewired to 10 volts and will p
32. is depressed If they are not tracking properly oscillators in tune with each other on the lowest note will not be in tune with each other on the highest note TRACKING FREQUENCY VCO1 2 2 3200 1600 5 6 800 Z NCO 2 Not tracking 400 with the other 200 100 oscillators 2 3 4 VOLTS 2 5 3 2 3 TYPES OF OSCILLATOR MODULES Several types of oscillator modules have been used in the 2600 the 4017 4027 and most recently 4027 1 They are equivalent except for the 4017 and 4027 modules require an external high frequency compensating trimmer to prevent the pitch from going flat at higher frequencies The 4027 1 is internally compensated so this trim is unnecessary BOTTOM VIEWS 4027 amp 4017 The 4017 and 4027 have from 15 to 18 pins the 4027 1 has only 7 Some units containing the 4027 1 may still have the high frequency track trimmer on the board but it is not connected to the module 324 REPLACEMENT The 4027 1 replaces all other oscillator modules If only one module is to be replaced in a unit contain ing the 4017 or 4027 modules follow the 4027 1 26 Noise Generator Voltage Processor Sample amp Hold Internal Clock Amplifier 2 6 1 NOISE GENERATOR Module 4022 The Noise Generator provides a 20 volt peak to peak noise signal of about 10 octaves bandwidth The right Noise Generator slider controls the amplitude of the noise and the le
33. ising waveform to produce a suitable trigger pulse shape Pin 5 of the 4015 module is the S H output 264 INTERNAL CLOCK The clock is a low frequency square wave oscillator whose frequency is determined by the position of the rate slider The clock trigger output is hardwired to the S H and the Electronic Switch and has a separate square wave output which is also wired to the clock output jack and the shunt of the external gate input jack under the gate select switch 045 a uni junction transistor and capacitor C115 comprise a relaxation oscillator When C115 reaches the threshold of O45 about 5V O45 discharges C115 through R383 to 15V The charge path of C115 is through R313 clock rate slider and O44 A42 a comparator converts the sawtooth signal on C115 to a 30 volt peak to peak square wave whose duty cycle is determined by the position of R385 pulse width adjust The output of A42 routes the signal through CR47 to the S H and the Internal Clock Ouput 265 AMPLIFIER Two power amplifiers are included in the 2600 to drive the left and right monitor speakers The power amplifier is driven directly from the left and right output jacks and has no available output on the front panel other than the speakers and headphone jack The signal from the preamps connected through the speaker level sliders enter the power amp circuitry through C104 and R341 to the inverting input of A40 The feedback for the op amp is from the
34. ltage on the noninverting input of A9 and is used to set the duty cycle of the pulse wave on the output of 9 CRB rectifies the output of A9 so that the pulse wave is positive going only R104 and R89 reduce the amplitude of the pulse wave to about 10 volts peak to peak 2 4 Board3 VCF 4012 The VCF is a 24db octave low pass filter with a variable cutoff frequency fc and resonance Q As the fc is decreased the higher harmonics of a signal are attenuated until only the fundamental frequency is audible The fc of the filter is variable from approximately 10Hz to 10KHz When the fc is set as high as possible the filter is said to be open 15 Volt Supply O1 02 and CR1 are the voltage regulators for A1 The 15 volt supply derives its regulation from the 15 volt supply through R11 to the inverting input of A2 the 15 volt comparator The output of A1 controls O5 the 15 volt current amplifier Deviations in the output voltage are reflected through R11 back to the inverting input of A2 The noninverting input of A2 is referenced to ground through R4 15 Volt Current Limiting When enough current flows out of the negative supply to cause 7 volts drop across R15 turns on effectively shorting the base of Q5 to the output voltage of the 15 volt supply 05 in turn supplies less current to the output ADJUSTMENT NOTE THIS ADJUSTMENT MUST PERFORMED PRIOR TO MAKING ANY OTHER CALIBRATIONS 1 Conne
35. n 3 from the symmetry trimmer R18 The 10V P P sawtooth wave from the module is applied to the inverting input pin 2 of A8 A8 is a comparator which compares the sawtooth wave against the voltage supplied by the symmetry trim mer R18 rectifies the output of 8 so the pulse wave is positive going only R50 and R51 reduce the amplitude of the pulse wave to about 10 volts peak to peak 23 2 VCO2 VCO 2 generates sawtooth pulse triangle and sine waveforms The width of the pulse wave can be controlled either by the pulse width slider or by a control voltage applied to the pulse width modula tion input This input is normally prewired to the Noise Generator output The Keyboard Control Voltage Sample and Hold ADSR and VCO 1 square wave outputs are prewired to the frequency control inputs of VCO 2 The 4027 1 oscillator is exactly the same as the 4027 1 module in VCO 1 The difference between the two oscillators is in the waveform converters Pulse Converter The pulse converter on VCO 2 is similiar to the square wave converter on VCO 1 The sawtooth wave from the 4027 1 module enters board 2 1 the waveform converter board on con nector pin 2 and enters the inverting input of A15 through R109 A15 is a comparator which compares the sawtooth wave against the output of A14 A14 sums the voltage from the pulse width control R20 and the pulse width modulation signal entering through slide pot R82 CR14 rectifies the out
36. n and remove any wire connected to the tip 7271 wires to tip wire and check continuity tip to shunt NOTE See section 6 of the 2600 SERVICE MANUAL for details of mini jack repairs x 02173 617 861 6890 ARP INSTRUMENTS INC 45 Hartwell Avenue Lexington SN 002 SERVICE NOTES MODEL 2600 DATE 9 25 74 SUBJECT MATING 2600 MAIN CONSOLE TO 3604P KEYBOARD PROBLEM All three oscillators on the 2600 are in tune with each other across the whole keyboard but the octaves are incorrect CAUSE When the 2600 the 3604P are serviced separately they may be adjusted to a slightly different standard resulting in a slightly different interval setting SOLUTION Reset the fixed interval control on the keyboerd 2600 CONSOLE AND 3604P MATING PROCEDURE 1 Put all of the slide switches on the keyboard in the righthand position 2 Pin low on the keyboard 3 Using the Initial Frequency slider on the front panel of one of the oscillators tune the oscillator to a frequency standerd 100 Hz on a frequency counter low on a strobe tuner or to another oscillator which has been disconnected the keyboard 4 Pin the highest C on the keyboard 5 Using a large screwdriver adjust the Fixed Interval control on the keyboard for exactiy four octaves higher than low DO NOT LOOSEN THE LOCKING NUT WHILE ADJUSTING THE FIXED
37. not to damage any of the com ponents as you lift the panel out 2 Remove the four screws that hold the handle on top in place 4 Lay the panel on something soft such as foam rubber or a blanket to prevent damage to the panel X 3 3 3 5 2 VOLTS PER OCTAVE VCF Ref No Trimmer Specifications Trim Procedure R153 1V OCT Repeat steps 1 5 for frequency calibrate disconnect dummy plug 2 Connect keyboard to console and depress low C 0 volts 3 Adjust initial frequency slider and fine tune slider for 200Hz 4 Depress C three octaves higher and adjust R153 for 1600Hz 3 volts 5 Repeat steps 2 4 until low C remains at 20082 and remains at 1600Hz 3 5 83 OUTPUT OFFSET R162 Output Offset 1 Monitor VCF output with an oscilloscope 2 Initial frequency fine tune and resonance slider left 3 All input sliders down 4 Adjust 162 for minimum d c output Movement of the initial frequency slider should not cause more than 1 volt deflection 3 5 4 GAIN ADJUST R163 Gain Open VCF initial frequency slider left 2 Resonance slider minimum 3 Raise 1 square wave input slider into filter and adjust R163 for same amplitude as measured at VCO 1 output NOTE You are adjusting for Unity Gain 3 6 Board 4 Adjustment Voltage Controlled Amplifier 3 6 1 LINEAR GAIN R196 Linear Gain Monitor VCA output with
38. oo soon Control Voltage too late 52 Types of Keyboards The 2600 has been manufactured with two types of keyboards the 3604P single note and the 3620 two note 5 2 1 3604P THREE BUS KEYBOARD The earlier model 2600 s used a model 3604P keyboard which has only single note capabilities This means that one pitch control voltage is generated at a time Each key has three contacts TONE INTERVAL VARIABLE FIXED TUNING PORTAMENTO b 3604 Features One memorized CV Tuning Control Portamento and Variable Interval which produce gate trigger and control voltage The calibrations and adjustments are covered in Section 6 5 2 2 3620 TWO BUS KEYBOARD More recent 26005 are using the 3620 model keyboard Technical data available in 3620 Service Manual See Section 6 for 3604P to 3620 conversion information 9 Te cuu tts 3620 Features Two separate memorized Control Voltages Interval Latch Repeat Modes LFO Delayed Vibrato Transpose Pitch Bend SECTION 6 MISCELLANEOUS NOTES 6 1 Troubleshooting Hints 6 1 1 POINTS TO REMEMBER Typically most 2600 failures are mechanical problems pinched wires broken slidepot etc Problems are likely to be D jacks or internal con nections via molex connectors Beware of monitoring jack outputs to determine faults often the problem
39. ower supply filter capacitors should be shown and R13 and R11 should have their reference designations reversed PAGE 107 R14 and R18 should be reversed on the layout yel Avenue Lexington MA 02173 617 861 6000 INSTRUMENTS INC 45 SERVICE NOTES MODEL 2600 DATE 10 25 74 SUBJECT KEYBOARD CONNECTING CABLE PROBLEM The keyboard interval setting changes and the pitch of the oscillators tends to go flat at the upper end of the keyboard CAUSE The keyboard connecting cable is not making a good electrical connection to the 2600 console Especially with the non molded type SOLUTION Clean both the male and female ends fo the keyboard connecting cable and 2600 conscle with tuner cleaner or other suitable cleaning solvent If necessary twist the pins on the cable and the keyboard about five degrees to insure a good electrical connection CLEAN ARP INSTRUMENTS INC 45 Hartwell Avenue Lexington 02173 677 861 6600 SN 003 SERVICE NOTES s MODEL 2600 DATE 9 25 74 2 SUBJECT MINI JACK REPAIRS PROBLEM Mini jack fails to conduct from the tip to the shunt CAUSE Tip wire of the mini jack is under tension from the solder mounting SOLUTION Heat the tip wire solder connection and push the tip wire down to the correct position 2 Push tip wire down and move it side to 1 Heat wire with soldering iro
40. part number 42A when ordering the new type jack SHUNT TIP NOTE 1 Care should be taken not to bend the tip of the jack when mounting replacement jacks to the front panel 2 When removing the printed circuit boards for servicing take care not to break the jumper wires connecting the jacks to the PC board 3 Be sure to remove the two screws holding the printed circuit board in place near the bottom of the board when servicing the electronics ARP INSTRUMENTS INC 45 Hartwell Avenue Lexington 02173 617 861 6000 SN 0 12 SERVICE NOTES MODEL 2600 DATE 11 1 74 SUBJECT REVERB WIRES PROBLEM The wires in the reverb unit break causing the reverb to be dead CAUSE The wires connecting the input and output jack to the reverb pickup and driver are flexed by the movement of the spring mounted reverb assembly SOLUTION Apply RTV silicone rubber to the wires on the input and output Jacks and the reverb driver and pickup coils to prevent the wires from flexing APPLY BTV APPLY RTV ARP INSTRUMENTS INC 45 Hartwell Avenue Lex ington 02173 617 861 6000 9 il Q f SECTION 5 2600 UPDATES 5 1 2600 Trigger PAGE 9 OF 9 Problem When interfaced with String Ensemble the 2600 s keyboard cannot trigger the ADSR Cause synthesize a delayed trigger the trigger output of the
41. plete amplified wave then passes through R281 to the reverb spring driver located on the bottom of the console case to give the reverb effect The other end of the reverb springs the pick up is AC coupled through C94 to pin 2 of A30 which amplifies the signal and sends it to the two reverb sliders There the two signals are split into the different channels left and right The left channel signal goes directly from the reverb slider to A29 where it is amplified and mixed with the left mixer signal The right reverb signal goes directly to the noninverting input pin 3 of A31 where it is amplified and sent to the reverb output jack The shunt of the reverb output jack is wired to the input of A27 so the right reverb signal can normally be mixed with the right mixer signal and will pass audio and DC signals applied to its input When the fc is set to the lowest frequency the filter is said to be closed and it will completely attenuate all audio frequencies The fc can be controlled manually by the Initial Frequency Slider and the Fine Tune Slider as well as by control voltage signals applied to the control inputs The fc range is adjustable from 10Hz to 10KHz without external inputs and can be made as low as 1Hz or as high as 20KHz with additional negative or positive control voltages The keyboard is prewired to the VCF control input through the 1V OCT trimmer which is tuned so that the fc of the filter tracks th
42. put of A15 so that the pulse wave is positive going only R116 and R118 reduce the amplitude of the pulse wave to about 10 volts peak to peak Triangle Converter 01 Q2 and A16 convert the sawtooth to a triangle wave The sawtooth wave passes through R113 to O1 an emmiter follower R115 the symmetry trimmer sets the DC offset of the sawtooth at the emmiter of 01 As the voltage at the base of Q2 rises from OV to about 5 Q2 s collector voltage drops from 10 to 5 As the voltage at 02 base rises from 5 to 10V the base collector junction of Q2 becomes forward biased and the voltage at Q2 s collector heads back toward 10V A16 amplifies the resulting 5 P P triangle wave to about 20 volts peak to peak and R125 removes the DC component R132 and 3 attenuates the output to 10 volts peak to peak Sine Converter The triangle wave at the output of A16 is applied to the sine wave converters Q3 and A17 through attenuator R121 purity trimmer O3 s nonlinearity rounds the peaks of the triangle to approximate a sine wave A17 amplifies the signal from Q3 to 10 volts peak to peak 2 3 3 3 The 4027 1 oscillator module is exactly the same as the module in VCO 1 The pulse wave converter of VCO 3 is exactly like the square wave converter of VCO 1 except that the symmetry trimmer is replaced by a slider on the front panel for manually variable pulse width control R92 the pulse width slider sets the exact level of the vo
43. r is prewired to the envelope follower input A1 CR2 and A2 comprise a full wave rectifier for the audio signal The positive portion of the wave on pin 6 of A1 goes through CR2 and into the non inverting input of A2 pin 3 The negative portion of the wave passes through to the inverting input 2 of A2 so that the output of A2 is always positive The rectified signal on pin 6 of is then filtered R12 15 and 7 10 and then amplified and buffered by A3 2 2 3 RING MODULATOR The Ring Modulator is an analog multiplier which accepts two different signals and multiplies them to form a single complex wave In the audio mode the DC component of each of the input signals is cancelled before it reaches the modulator In the DC mode the output voltage of the ring modulator will be the product of the two input voltages divided by 5 The Ring Modulator is useful for producing bell or gong sounds In the DC mode it can also be useful as a second voltage controlled amplifier by applying a control voltage to one input and an audio signal to the other input The Ring Modulator will pass the audio signal with an amplitude proportioned to the control voltage VCO 1 sawtooth ouput is prewired to the left input and VCO 2 s sine wave output is prewired to the right input 2 3 Board 2 2 1 VCO 1 VCO 2 VCO 3 GENERAL The voltage controlled oscillators generate sawtooth wave whose frequency is determined either
44. roduce 10 volts on the inverter output when the slider is fully right The lag processor acts to smooth out sharp rising and falling voltages When the slider is fully left lag time constant is about 05 milliseconds When the slider is fully right the delay is about 5 seconds The lag processor is used whenever a low frequency signal needs to be filtered or rounded out The input is prewired to the output of the Envelope Generator 2 6 3 SAMPLE amp HOLD MODULE 4015 The S H provides a stepped output voltage by sampling and storing the instantaneous voltage level of the input signal each time it receives a trigger pulse This stored voltage is held until the next trigger pulse occurs The S H trigger input is prewired to the Internal Clock but the S H can be triggered from any sharply rising waveform The S H input is prewired to the Noise Generator output The left S H slider level attenuates the input signal before it is sampled thus lowering the average voltage level on the S H output The right slider rate does not actually belong to the S H but it controls the rate of the Internal Clock which may be used to supply a trigger and therefore controls the sample rate The signal that is to be sampled enters pin 1 of the 4015 module through the level slider on the 5 board The pulse that instructs the module to sample the voltage of the signal on pin 1 enters the module on pin 4 C119 and R392 differentiate any sharply r
45. the front panel is at maximum the signal will pass through the VCA with no change in amplitude unity gain If the gain slider is at a minimum no signal will pass through the VCA unless a positive control voltage is applied to either of the two control inputs The sensitivity of the left control input is linear but the response of the right control input is exponential The left control input is prewired to the AR and the right control input is prewired to the ADSR output There are two audio inputs to the VCA the left input is noninverting and the right audio input is inverting Thus a positive going sawtooth wave applied to the right audio input produces a negative going sawtooth wave on the output of the VCA The left audio input is prewired to the VCF output and the right audio input is prewired to the Ring Modulator output Pin 1 is the noninverting audio input and pin 2 is the inverting audio input of the 4019 module Pin 3 is the linear control input and pin 4 is the exponential control input R196 the linear gain trimmer sets the sensitivity of the linear input and R195 the exponen tial gain trimmer sets the sensitivity of the exponen tial control input this trimmer is always set in the fully clockwise position R198 the initial gain slider adds voltage to the linear control input to allow signals to pass through the VCA without external contro voltages The control reject trim mer R193 eliminates any leakage of th
46. tor of Q6 also travels through CR6 R12 and 179 attack slider and begins to charge up and 02 A1 buffers and follows the voltage level on C1 and C2 when the voltage reaches 10 volts O5 turns on which turns Q7 through 684 and R18 Q7 then grounds out the voltage on the base of O8 thus unlatching Q8 and 06 When Q6 turns off CR7 is reversed biased which allows O4 to turn on The 10 volts on C1 and C2 discharges through the decay slider R180 to the voltage level present on C68 on board 4 Q6 on board 4 holds C68 to a voltage level determined by the position of the sustain slider R181 When the gate voltage is removed O2 turns off and the voltage on the collector of Q2 rises which turns off O4 through CR3 and turns on O3 through CR1 The remaining voltage on C1 and C2 discharges to ground through the release slider R182 25 4 MIXER PREAMP The Mixer is a general purpose mixer useful for audio or DC signals 115 output goes directly to the pan slider through the pan output jack and to the reverb erator input The two inputs of the mixer are prewired to the VCF and the VCA The jacks above the mixer input sliders will disconnect the slider from the mixer input when a patch cord is inserted so that the slider can be used as general purpose attentuators in other functions of the 2600 The outputs of the pan slider go to the left and right preamplifiers Signals enter the mixer circuitry through either slider R200 or R
47. y sequentially from left to right 5 Each key should produce a well defined sharp pulse of sound If not then either the sequence of contact closures is incorrect or the contacts and or bus bar are dirty 6 Contacts and bus bars should be cleaned with Trichlorethylene denatured alcohol or some other 0 residue cleaner 3604P V OCT ADJUSTMENT 1 Pin low C on the keyboard while monitoring the KBD CV output jack on the console 2 Adjust trimmer on A1 module for O Volts output Note some of the older style 3604P keyboards contain the encapsulated module If so adjust R19 trimmer on the keyboard for 0 Volts 3 Depress high C and adjust the fixed interval pot 2 5Kohm for exactly 4 00 Volts Be sure Interval switch on panel is selected to the right when making this adjustment 6 2 3 CONTACT ADJUSTMENTS To adjust the contacts use a small screwdriver at the base of the spring contact Pivot the screwdriver against the base of the spring by anchoring one edge of the screwdriver on the P C board This will give you the control you need to adjust the contacts without bending them too far CONTACT SPRING ADJUSTMENTS Clean the contacts with denatured alchohol before adjusting them 7 CAUTION IMPROPER ADJUSTMENT WILL CAUSE SPRING BREAKAGE MODIFICATIONS 3620 Modification Older style keyboards 3604P can be converted to the new 3620 These modifications are only avail able at the Factory by appointm
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