902 Voltage Controlled Amplifier Test Procedure

Connect de voltmeter to TP-L (collector of Q5) low side to ground. 2. Turn FIXED CONTROL VOLTAGE pot to 6 and set CONTROL MODE switch to EXP. DC vottage should read approximately zero. 3. Rotate FIXED CONTROL VOLTAGE pot to 0. DC voltage should read approximately +0.24V. 4. Set CONTROL MODE switch to LIN. DC voltage should read approximately + 1.2V. 5. Rotate FIXED CONTROL VOLTAGE pot to 6. DC voltage should read approximately -4.8V.

962 Sequential Switch A Testing And Alignment

Lamp L1 should light within one second. Lamps L2 and L3 may light first. 2. Operate pushbuttons S1, S2 and S3. Ap- 30TTOM VIEW propriate stages should turn on as well as V-TRIG 2N4058 INPUTS, J2, J3 and J4 respectively. A suitable input is +3.6 volt buss on the pushbutton. 3. Trigger outputs should be approximately 3.6 volts when stage is active. Test to see that they function as V-Trigs. 4. Shift input at J1 takes a positive going signal at least 0.3 volts high. Oscillator outputs...

Applications

When a dynamically varying signal is applied to the input of the 905, the output will consist of a series of closely spaced echoes, the subjected effect of which is similar to that of reverberation of sound. If a small amount of ''echo signal is mixed with a larger amount of direct signal (REVERBERATION Control set slightly clockwise), the effect ot a typical concert hall is obtained. If the echo signal only is passed (REVERBERATION Control set fully clockwise), an exaggerated echo suggesting a...

Checkout Procedure

Check the output of the adder section as follows Measure the voltage at the collector of Q5. This voltage should jump about -0.075 volts each time the top FIXED CONTROL VOLTAGE switch is advanced one step. When both FIXED CONTROL VOLTAGE knobs are set on 0, the voltage should be approxinnately +0.1 volts. If these voltages at the collector of Q5 are observed, then the adder section works properly. If not, check all components in the adder section. 2. Place a 2N4058 transistor in the Q10 socket,...

Normal Operating Voltages

The following direct voltages are measured with a transistor or vacuum tube voltmeter with an input impedance of 10 megohms. Voltages of properly operating units may vary as much as -5 from these values. Set the front panel controls as follows WIDTH OF PULSE WAVEFORM Full counterclockwise. Nothing should be connected to the front panel jacks. All lower console voltage switches should be off. Large deviations from these voltages (See Table 1 on Figure 6) indicate trouble in the unit

Retracking Of 901b Oscillators

Follow steps 2 thru 5 in paragraph D. 2. Pick any oscillator as the reference oscillator. Adjust tracking trimmer (P2) of the other oscillators, one at a time, until the entire bank is in tune. Use a long blade aligning screwdriver for this operation. 3. Repeat entire procedure once or twice, or until perfect tracking is obtained.

Info

Adjusts + output balance for exponential dc voltages with FIXED CONTROL VOLTAGE CONTROL fully counterclockwise. Adjusts zero output offset with FIXED CONTROL VOLTAGE control fully counterclockwise. Adjusts zero output offset with FIXED CONTROL VOLTAGE control fully clockwise. Adjusts amplitude level balance between linear and exponential mode with FIXED CONTROL VOLTAGE control full clockwise.

Note

If unable to adjust, substitute a new 2N2646 (Q10). 3. Check triangular output as in step 2. DC should be 0-50 mv, ac approximately 650 mv RMS. Adjust triangle waveform trimpot (P3) for minimum glitch and best waveform symmetry. If a non-symetrical waveform still exists, advance tracking pot (P2) and readjust triangle waveform (P3). If symmetry is still not possible, R8 and R9 may have to be changed. After final adjustment, the following conditions should exist Sawtooth output 0.50 volts ac...

P

Permanently install the proper shunt resistor (approximately 2.2K) and set REGENERATION control between 7 and 8. 12. Check to see that the cutoff frequency decreases one octave for each one volt decrease in control voltage. Use RANGE 2 and FIXED CONTROL VOLTAGE of 0. Adjust generator frequency so that output is at -3db (260 to 340Hz). Set FIXED CONTROL VOLTAGE at -5.5 volts and apply +5 volts to one of the CONTROL INPUTS. The output should be -3 2db. Set FIXED CONTROL VOLTAGE at +5.5 volts and...

Q

Vary the range of FREQUENCY control and observe that voltmeter will vary from +0.5 in full counterclockwise position to -0.5 in full clockwise position. R. Connect dc voltmeter to point A and set WIDTH control to mid-position. DC level indication should be -1.5 +0.2 volts. S. Turn WIDTH control to full counterclockwise position and apply +4.0 volts to one of the WIDTH control inputs. Voltmeter should indicate - 1,0 0.010 volts. T. Check the other WIDTH control for the same result as in step S.

Test Procedure

Connect a 100K ohm resistor between CS-8 and CS-21 and also between CS-10 and CS-19. 2. Connect vacuum tube voltmeter (VTVM) at 680-ohm resistor in coupler section. Turn BANDWIDTH and CENTER FREQUENCY controls in full clockwise position. VTVM should indicate 0 volts. 3.Turn CENTER FREQUENCY control fully counterclockwise. VTVM should indicate +1.60 volts. 4.Turn BANDWIDTH control counterclockwise. VTVM indication should vary from +1.60 volts to +5.00 volts. 5.Turn COUPLER switch from BAND...

Trouble

+15V (M1), -15V (M2), +12V (M3), -6V (M4) Output Current 1.5A (M1, M2), 1.7A (M3),2.5A < M4) Line Regulation 0.075 (M1 thru M4) Load Regulation 0.075 (Ml thru M4) Ripple Peak-to-Peak 5mV (M1 thru M4) Over Current 50 -130 of full rated load (M1 thru M4) Over Voltage 105 -135 of ratings (M1 thru M4) VOLTAGE ADJUST - Adjust output voltage to desired level at no load with unit connected as shown in Figure A. Ascertain that OVP (Figure B) is n maximum clockwise position.

Waveforms

B. Check SAWTOOTH output level for approximately - 6dB. C. Check TRIANGULAR output. Adjust (T) for no glitch on lowest frequency, adjust (2) for 0 DC offset and check level for approximately -6dB. D. Check RECTANGULAR output (921A WIDrH to 50 ). Adjust (3) for square E. Check SINE output. Alternately adjust ( ) and Qj) for sine shape and symmetry, adjust (6) for 0 VDC offset and check level for - 4dii.

Caution

Do not run units over five minutes without additional heat sink. OVP ADJUSTMENT - Remove input power and load and apply an external voltage through a limiting resistor as shown in Figure C. Adjust OVP ADJUST until firing occurs at desired voltage as the external source is slowly increased. Select limiting resistor to limit current to 0.5 ADC maximum after firing. Low output voltage, poor regulation, high ripple, loaded. High output voltage, poor regulation, high ripple, loaded. High output...

Range Switch Scaling

If using a Model 950 or 951 Keyboard, depress and hold C3. If a Model 952 Keyboard is used, depress and hold C5. Adjust (A) for 2093Hz (or two octaves above reference). B. Switch RANGE to 32'. Adjust (5) for 130.8Hz (or two octaves below reference). C. Check all RANGE positions for 0 - 1 Hz. C. Apply a unison (523Hz) - 2dB to OdB square wave to the SYNCH, input. Rotate FREQUENCY pot clockwise and counterclockwise from 0. Locking range should be at least 2 semitones on...

Retracking Of 901b Oscillators With Serial Numbers Under 1912

Reduce the FIXED CONTROL VOLTAGE controls on the oscillator so that the total is 0. The oscillator frequencies will, of course, be lowered five octaves, and may be out of tune with one another. Pick oscillator which is producing the lowest frequency. This oscillator is the reference oscillator, and will not require a tracking resistor. Connect a resistance substitution box as the tracking resistor to each of the other oscillators in turn. Find resistors that bring the oscillators in tune with...

Tuning Procedure

The 901A adjustments should be set only after the 901B oscillators have been adjusted to track properly as described for the 901B and the 901A has been allowed to run in the cabinet with the 901 B s for at least ten minutes. The instruments should be at room temperature. 1. Set the two FIXED CONTROL VOLTAGE controls on the 901A panel to 0. 2. Connect an accurately calibrated voltage source, which is stable to within 0.1 , to one of the control inputs of the 901 A. For instance, the pitch...

951 Keyboard Tuning

The keyboard has two adjustments to be made. The scale adjustment adjusts the current source so that the total drop across the resistor string is 5.000 volts. The range adjustment fixes the lowest key at zero volts. Adjustments are made with the external range and scale controls on the five mark. 2. Adjust the range setting with the trimpot. If adjustment cannot be made within the range of the trimpot, it may be necessary to short one or both of the two resistors in series with it. 3. Adjust...

Probable Cause

(3) OVP triggering with Q2, Q3, CR6 shorted (4) CR1, CR2, CR3, CR4, C1 or C2 shorted (1) Possible overload or current limit adjust R11 improperly adjusted (should be set for 120 of full load current prior to feedback) (2) Possible OVP triggering (check setting of R22) (4) C1, CR5, R4( C3, Q1, C4, R11, R14, R15, CR8 or C6 shorted (2) Q2, Q3, CR6, R3 or R16 shorted (2) SCR1, Q4, CR7, R21 or R22 shorted (1) SCR1, R17, Q4, CR7, R21 or R22 open (2) Inadequate heat sinking or heat sink bolted to...

11

Connect the 956 Ribbon Controller to the test rack. Patch TRIGGER output of the 956 to the 911 Envelope Generator, then to the 902 Voltage Controlled Amplifier. Connect SIGNAL OUTPUT of a voltage controlled oscillator to the 902 SIGNAL INPUT. Connect 902 SIGNAL OUTPUT to a monitor amplifier and speaker. Connect PITCH output to the voltage controlled oscillator CONTROL INPUT. Touch TRIGGER bar on the 956. Oscillator should be heard. Adjust the 911 and 902 for a square envelope. Set SCALE to 1...

Notes

L.Set wirewound trimpots R17 and R25 to mid-position. 2. Set FIXED CONTROL VOLTAGE to 6, FREQUENCY RANGE to 2 and REGENERATION to 0. 3. Using a dc voltmeter, check the voltages at R35 and R39. Both levels will be approximately 1.0 volts. Adjust R40 (zero trimpot on filter board) for approximately the same voltage at R35 and R39. 4. Connect DC VOLTMETER across R23 (470 ohms) and adjust 2.0 volt LEVEL trimpot (R24) for 2.0 volts. Disconnect DC VOLTMETER after adjusting. 5. Apply a 20kHz Odb...

General

The 905 Reverberation Unit utilizes a dual spring-type acoustic delay line to produce a succession of decaying echoes of an audio signal. A single panel control determines the ratio between the amounts of reverberated and non-reverberated signals that appear at the output jack. The front panel control does not alter the characteristic decay time of the echoes, since this is a function of the delay line itself. Instructions for mounting and connecting of power, and input and output...

904a Voltage Controlled Lowpass Filter Test Procedure

L.Set wirewound trimpots R17 and R25 to mid-position. 2. Set FIXED CONTROL VOLTAGE to 6, FREQUENCY RANGE to 2 and REGENERATION to 0. 3. Using a dc voltmeter, check the voltages at R35 and R39. Both levels will be approximately 1.0 volts. Adjust R40 zero trimpot on filter board lor approximately the same voltage at R35 and R39. 4. Connect DC VOLTMETER across R23 470 ohms and adjust 2.0 volt LEVEL trimpot R24 for 2.0 volts. Disconnect DC VOLTMETER after adjusting. 5. Apply a 20kHz Odb sinewave to...

Contents

TITLE PAGE SYN 2A 993-042141 Figure 1 Console 3 993-042644 Figure 2 Console 3A 993-042239 Figure 3 Control Panel Mixer 3 4A 993-042185 Figure 4 Console 35 993-042184 Figure 5 Console 901A 993-042645 Figure 6 Oscillator 901B 993-042646 Figure 7 Oscillator 901C 993-042647 Figure 8 Output 902 993-041813 Figure 9 Voltage Controlled 903A 993-041818 Figure 10 Random Signal 904A 993-041805 Figure 11 Voltage Controlled Low Pass Filter 13 904B 997-041807 Figure 12 Voltage Controlled...