221 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,...

Cause Spring Breakage

Older style keyboards (3604P) can be converted to the new 3620. These modifications are only available at the Factory by appointment only cost 350. Included with the modification is a portamento interval footswitch and a one full year warranty. Call the Factory for more details. The 4012 to 4072 Filter conversion is available for all 2600's. See Section 5 page 12 for installation information. 1. Remove the 115 V wire from the terminal strip. 2. Solder the 220 V wire to the terminal strip. 3....

Contents

SECTION 2 - Circuit Descriptions 1 SECTION 4 - Assembly & Disassembly 11 SECTION 5 - Revisions Changes 12 SECTION 6 - Miscellaneous Notes 13 SECTION 7 - Diagrams, Schematics & Assemblies 16 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...

Effect

Sound becomes audible before ADSR is initiated No sound at all ADSR is not initiated Pitch changes before previous envelope has completed Previous note is heard before correct note 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 become necessary to remove each of the suspected active components, one at a time. signal to be passed by the VCA or VCF). The trigger is delayed...

Ervice Motes

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. .

Info

SECTION 4 ASSEMBLY & DISASSEMBLY 1. Remove the three screws on each side of the front panel. 2. Remove the four screws that hold the handle on top in place. 3. Using two dummy plugs in jacks as handles on the lower portion of the panel, lift the panel up and then out from the bottom. Take care not to damage any of the components as you lift the panel out. 4. Lay the panel on something soft such as foam rubber or a blanket to prevent damage to the panel.

Inverted Output

Fzam P .n pn p F R r *a KHS f-K - r'. if 2 I < SUBJECT 2600 SERVICE MANUAL CORRECTIONS 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 & 37 A 10K resistor should be shown from pin 2 of A20 (AR circuit) and A1 (ADSR circuit) to ground. PAGE 100 The keyboard connecting cable pin connections should be shown, the power supply filter capacitors should be shown...

Keyboard Contacts Access

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 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.

R128 R121

Monitor VCO 2 sine wave output with an oscilloscope. 2. Adjust R128 for 10V P.P. output. 3. Adjust R121 for the best sine waveform. *N0 TE It may be necessary to readjust calibrations after performed in the order listed. *N0 TE It may be necessary to readjust calibrations after performed in the order listed. 3.5 Board 3 Adjustments - Voltage Controlled Filter

R196

Monitor VCA output with an oscilloscope. 2. Patch VCO 3 sawtooth to VCA 'VCF Audio Input' jack and raise audio input slider fully. 3. Put the initial gain slider fully left (minimum). 4. Raise VCA AR control slider all the way. 5. Depress and hold the manual start button and adjust R196 for 10V P.P. maximum signal output.

R34 R35

Put audio d.c. switch to d.c. position. 2. Raise VCO 2 slider into the Ring Modulator only. 3. Monitor Ring Modulator output with oscilloscope and adjust R33 (middle trimmer) for minimum output (should be less than 10mv). 4. Put audio d.c. switch to audio position and adjust R34 (lower trimmer) for minimum output (should be less than 10mv). 5. Raise both sliders into Ring Modulator and select audio d.c. switch to d.c. 6. Adjust R35 for 20V P.P. maximum.

Section 1 General

The 2600's 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. Synthesizers include three types of circuits 1) signal sources, 2) signal modifiers, and 3) controllers. In general, sounds are produced by a synthesizer in...

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). Voltage Source BR1, 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...

Section 3 Calibrations

The following section includes all the calibrations in the 2600. NOTE THIS ADJUSTMENT MUST BE 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 +15.00VDC. 3. Connect the DVM across the negative supply connection and ground (black and violet). 4. Adjust R13 for exactly -15.00VDC.

SEiRvsce Jiotes

When interfaced with a String Ensemble, the 2600's keyboard cannot trigger the ADSR. To synthesize a delayed trigger, the trigger output of the 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. Add a blocking diode in a patch cord form the inverter output to the tirgger input of the 2600. 1. Cut open the patch cord and connect the diode in series with...

Shunt

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.

Snc09

PROBLEM The keyboard interval setting changes and the pitch of the oscilhtors tends to go flat at the upper end of the keyboard. CAUSE The keyboard connecting cable is not making a good elcctrical connection to the 2600 console (Especially with the non-molded type connector). SOLUTION Clean both the male and female ends fo the keyboard connecting cable and 2600 console with tuner cleaner or other suitable cleaning solvent. If ncccssary, twist the pins on the cable and the keyboard about five...

251 Voltage Controlled Amplifier

The VCA controls the amplitude of a signal passing through it. When the initial gain slider on 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...

322 Tracking Definition

Oscillators which are tracking together will maintain The 4027-1 replaces all other oscillator modules. If only one module is to be replaced in a unit containing the 4017 or 4027 modules, follow the 4027-1 2.6 Noise Generator, Voltage Processor, Sample & 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...

Servi

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 incorrcct. CAUSE When the 2600 or the 3604P are serviced separately they may be adjusted tc a slightly different standard resulting in a slightly different interval setting. SOLUTION Reset the fixed interval control or. the keyboard. 2600 CONSOLE AND 3604P MATING PROCEDURE . 1. Put all of the slide switches on the keyboard in the...

Model 2600 Block Diagram

Arp 2600 Diagram

Raise VCO 1 slider into the filter and close VCF 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 key 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....