Octave Voyetra Eight Owner's manual

Voyetra Eight Hardware Maintenance Manual
Revision 1.0a
Revision Date Changed By Reason
1.0 ??/??/1984 Carmine J. Bonanno Original Revision
1.0a 06/19/2002 Joan Touzet
[email protected]
http://www.atypical.net/
Mistake correction
Revisions for clarity
Started schematic entry
“Copywright [sic] 1984 by OCTAVE-PLATEAU ELECTRONICS, INC.
51 Main Street
Yonkers, New York 10701”

Table of Contents
1INTRODUCTION............................................................................................................................... 4
1.1 TRACKING DOWN VOICES ............................................................................................................ 4
1.2 IS ANYTHING REALLY WRONG?................................................................................................... 4
1.3 DOES THE INSTRUMENT NEED A CALIBRATION?............................................................................ 4
1.4 CARD SUMMARY .......................................................................................................................... 6
1.4.1 Mixer Card.............................................................................................................................. 6
1.4.2 VCO Card ............................................................................................................................... 6
1.4.3 VCF Card................................................................................................................................ 6
1.4.4 DAC Card ............................................................................................................................... 6
1.4.5 DIGIMOD Card...................................................................................................................... 6
1.4.6 ANAMOD 1 Card.................................................................................................................... 6
1.4.7 ANAMOD 2 Card.................................................................................................................... 6
1.4.8 CPU Card ............................................................................................................................... 6
1.4.9 Pot Panel................................................................................................................................. 7
1.4.10 Switch Panel....................................................................................................................... 7
1.4.11 Jack Bay ............................................................................................................................. 7
1.4.12 Power Supply ..................................................................................................................... 7
1.4.13 Keyboard ............................................................................................................................ 7
1.5 SIGNAL FLOW DIAGRAMS............................................................................................................. 8
2MIXER CARD................................................................................................................................... 10
2.1 THEORY OF OPERATION.............................................................................................................. 10
2.2 VCA OPERATION ....................................................................................................................... 10
2.3 HEADPHONES ............................................................................................................................. 11
2.4 NOISE ......................................................................................................................................... 11
2.5 CALIBRATIONS ........................................................................................................................... 11
3VCO CARD ....................................................................................................................................... 12
3.1 THEORY OF OPERATION.............................................................................................................. 12
3.2 VCO OPERATION ....................................................................................................................... 12
3.3 AUTOTUNE FUNCTIONALITY ...................................................................................................... 13
3.4 DC VOLTAGES............................................................................................................................ 14
3.5 CARD PIN SIGNALS ..................................................................................................................... 14
3.5.1 Inputs .................................................................................................................................... 14
3.5.2 Outputs.................................................................................................................................. 14
3.6 TROUBLESHOOTING TIPS ............................................................................................................ 14
3.6.1 Step 50-71: Waveform Tests................................................................................................. 15
3.6.2 Step 72-73: Sync Check......................................................................................................... 15
3.6.3 Step 74-75: Linear FM Check............................................................................................... 15
3.6.4 Step 76-79: Modulation Test................................................................................................. 15
3.7 TYPICAL PROBLEMS AND SOLUTIONS ........................................................................................ 15
3.7.1 Letter “A” appears ............................................................................................................... 15
3.7.2 Letter “B,” “C” or “D” appears ......................................................................................... 16
3.7.3 Letter “E” appears or other pulse width problems .............................................................. 16
3.7.4 No sub octave........................................................................................................................ 16
4VCF CARD ........................................................................................................................................ 17
4.1 THEORY OF OPERATION.............................................................................................................. 17
4.2 VCF OPERATION ........................................................................................................................ 17
4.3 CALIBRATIONS ........................................................................................................................... 18
4.4 VCO MULTIPLEXING SYSTEM .................................................................................................... 19
4.5 DC VOLTAGES............................................................................................................................ 19

4.6 CARD PIN SIGNALS ..................................................................................................................... 19
4.6.1 Inputs .................................................................................................................................... 19
4.6.2 Outputs.................................................................................................................................. 20
4.7 VCF CARD TROUBLESHOOTING TIPS ......................................................................................... 20
4.7.1 Step 00-02: Resonance (Q) Tests ......................................................................................... 20
4.7.2 Step 03: DC Feedthrough Check ......................................................................................... 20
4.7.3 Step 04-11: Initial Fcand V/Oct Calibration ....................................................................... 20
4.7.4 Step 11-27: VCO Volume Test ............................................................................................. 21
4.7.5 Step 28-31: Fc& Q Modulation ........................................................................................... 21
4.7.6 Step 32-35: VCO1 & 2 Modulation...................................................................................... 21
4.7.7 Step 36-39: Noise Audio Path.............................................................................................. 21
4.7.8 Step 40-43: VCO Bypass VCF ............................................................................................. 21
4.7.9 Step 43: TL068 Drift Test..................................................................................................... 21
5DIGIMOD CARD ............................................................................................................................. 23
5.1 THEORY OF OPERATION.............................................................................................................. 23
5.2 DEMULTIPLEXING ENABLE SIGNALS .......................................................................................... 23
5.3 MODULATION SYSTEM SCAN CLOCKS........................................................................................ 24
5.4 DEMULTIPLEXING /REMULTIPLEXING ........................................................................................ 24
5.5 MONO CONTROLLER MULTIPLEXER ........................................................................................... 25
5.6 MISCELLANEOUS SWITCHING FUNCTIONS .................................................................................. 25
6KEYBOARD...................................................................................................................................... 26
6.1 THEORY OF OPERATION ............................................................................................................. 26
6.2 CIRCUIT OPERATION................................................................................................................... 26
6.2.1 Power Retrieval .................................................................................................................... 26
6.2.2 Clock/Strobe Retrieval ..........................................................................................................26
6.2.3 Digital Data Acquisition ....................................................................................................... 27
6.2.4 Analog Data Acquisition....................................................................................................... 28
6.2.5 Keyboard Pressure Sensor.................................................................................................... 28
6.2.6 Joystick.................................................................................................................................. 29
6.3 CALIBRATIONS ........................................................................................................................... 29
6.4 KEYBOARD TROUBLESHOOTING TIPS ......................................................................................... 29
7POT PANEL ...................................................................................................................................... 30
7.1 THEORY OF OPERATION.............................................................................................................. 30
7.2 KEYBOARD CLOCK/POWER INTERFACE...................................................................................... 30
7.3 KEYBOARD DATA INTERFACE .................................................................................................... 31
7.3.1 Digital Data Retrieval........................................................................................................... 31
7.3.2 Analog Data Retrieval .......................................................................................................... 32
7.3.3 Controllers ............................................................................................................................ 32
7.4 PARAMETER TRIMMER MULTIPLEXER ........................................................................................ 32
7.5 MASTER VOLUME AND MASTER TUNE CONTROLS..................................................................... 32
7.6 CALIBRATIONS ........................................................................................................................... 33

1 Introduction
1.1 Tracking Down Voices
From time to time, this manual will refer to calibrations for a particular
voice. These voices are numbered from 0-7 and are indicated on the
trimmer locations diagram. However, when troubleshooting, it is often
necessary to determine which voice is defective. The Set Page (see
appendix) provides a feature for disabling voices which may be used to
locate which voice is sounding.
1.2 Is Anything Really Wrong?
The Voyetra is a very complicated instrument and at times may generate
sounds which may seem to indicate a malfunction when none actually
exists. In case of question, the easiest way to determine if the instrument
is functioning properly is to load the Null Patch by pressing A440 and
then pressing Call Right and Call Left. This loads the instrument with a
known sound and the editing pages can be used to check for specific
features.
Alternately, the Quality Control/Calibration test tape may be loaded into
the instrument and the documented test procedure may be used to test
all system functions for proper operation.
It is strongly suggested that a problem be verified prior to attempting any
system troubleshooting.
Examples of non-existent problems are “puzzling” things like a changing
timbre that doesn’t always happen. Remember that the keyboard is
velocity sensitive and the timber change could very well be part of the
program. Other modulation routings can cause “weird” non-existent
problems such as detuning oscillators, strange tracking, etc.
1.3 Does the instrument need a calibration?
The Voyetra will rarely need calibrating since the most sensitive part of
the instrument, the VCO, is automatically calibrated when Auto Tune is
pressed. However, the VCFs, VCAs and Mod system do have
calibrations that may have to be tweaked.
The following list of sample problems may help in determining what
symptoms require specific calibrations:
One voice sounds “different” than the others.

First, determine what it is about the voice that is “different.” Is it the
“tone?” Then it may need a VCF calibration. Is it the “level?” Then it may
be a VCA calibration. Is it the “tuning?” Then it may need a Mod System
calibration, or a VCO may be defective.
If the tone is different, refer to the VCF section of the manual and
calibrate or troubleshoot the VCF circuits. If the level is different, refer to
the MIXER section and troubleshoot the VCAs. If the Mod System is at
fault, refer to the Mod System overview and then see whether it’s the
ANA1, ANA2, or VCF card. If there’s a VCO problem, refer to the VCO
section of this manual.
A strange “clicking” or “thumping” is heard whenever a key is pressed.
Is the click part of a patch? Play the null patch and see if it goes away.
Try turning off the VCOs in the null patch to see if it’s still there. Maybe
the VCA offsets on the mixer card need calibrating. Usually, only one
voice is out, so you’ll have to use the SET page to find the culprit.
One program is out of tune but the rest are O.K.
This sounds like a classic Mod System “problem” where VCO modulation
is on ever so slightly. A problem on “one program” is usually an indication
that the program rather than the instrument is at fault.
Pitch bend on the left is different than on the right.
This may be a Mod System setting, but it can also be a calibration on
ANA2 or the POT PANEL.

1.4 Card Summary
1.4.1 Mixer Card
Contains eight VCAs (one per voice) and a stereo mixer that sums the
system outputs. Calibrations include CVA offset trimmers and channel
gain trimmers. The MIXER also contains the Noise Source and various
other minor system functions.
1.4.2 VCO Card
Contains four VCOs. The system has four of these cards, two per side.
1.4.3 VCF Card
Contains four VCFs and modulation circuitry. The system has two of
these cards, one per side. Calibrations include filter scaling, initial filter
cutoff and initial filter resonance for each VCF.
1.4.4 DAC Card
Contains the Voice on/off functions, and the A/D and D/A functions,
which allow the CPU to control the analog system components.
Calibrations include DAC offset adjustment, reference trim and mod
system offset trim.
1.4.5 DIGIMOD Card
Contains system clocking logic for the modulation and DAC subsystem.
1.4.6 ANAMOD 1 Card
Contains the mod subsystem routing circuitry.
1.4.7 ANAMOD 2 Card
Contains high speed multiplexed VCAs for the mod subsystem.
Calibrations include VCA offsets and gain as well as an adjustment for
pitch bend LEFT and RIGHT balance.
1.4.8 CPU Card
Contains the host computer and memory circuitry for controlling the
Voyetra and memorizing patch settings.

1.4.9 Pot Panel
Contains the Keyboard and front panel parameter trimmer interface
circuits. Calibrations include pitch bend balance and gain, and X axis
gains.
1.4.10 Switch Panel
Contains LEDs and switches with interfacing circuits for connecting them
to the CPU.
1.4.11 Jack Bay
Contains interface jacks and an AGC circuit for the Tape input.
1.4.12 Power Supply
Contains regulators and fuses for +/- 15V, +5V, +11V, +22V, as well as
power-down detection circuitry for the battery backed-up RAM on the
CPU.
1.4.13 Keyboard
Contains digital and analog circuits to interface the keys and controllers
to the CPU via the Pot Panel.
FAN
JACK
Power Supply
ANA1 ANA2 DAC VCO VCO VCO VCO DIGI VCF VCF CPU MIX
MIX VCO VCF VCO VCO VCF VCO DAC DIGI ANA1 ANA2 CPU
POT
Figure 1-1 Card Placement inside the V8 Chassis

1.5 Signal Flow Diagrams
The following diagrams are included to assist in understanding some of
the Voyetra 8’s signal flow paths.
Mod Bank
VCAs
VCO1, VCO2 FcQ
22
2 2
VCO1
VCO1
2 2
2 2
VCO2 VCO2
Mono Contr.
MIX VCO VCF VCO VCO VCF VCO DAC DIGI ANA1 ANA2 CPU
POT
+/-x, Press (Mono Controllers)
Figure 1-2 Modulation System Signal Flow
JACK
MIX VCO VCF VCO VCO VCF VCO DAC DIGI ANA1 ANA2 CPU
VCO 1,2 VCO 1,2 VCO 1,2 VCO 1,2
Figure 1-3 Audio Signal Flow

Jack Bay
Mixer
Card
8
VCO 1
8
VCO 2
VCA
VOL 1
8
VCA
VOL 2
8
VCO Cards
8 VCF VCA
(8)
8 8
VCA VCA
VCA
VCF
Cards
Phones Volume
Phones Out
+15
Noise Gen
MM5837
VCA 2
Vol L/R
Right Mono Left
Master Outputs
Buffers
VCA VCA Programmable
CPU Vol L (Parameter Trim Volume)
CPU Vol R
Buffer
External Volume Pedal
+15
Master
Volume
+15
Pot Panel
Schematic 1-1 System Audio Path

2 MIXER Card
2.1 Theory of Operation
The MIXER Card consists of eight identical Voltage Controlled Amplifier
(VCA) circuits followed by mixing circuitry. In addition, certain other
related functions are placed on this card.
The functions on this board include:
•Eight channel demultiplexer for ADSR 2 voices 0-7
•Demultiplexing for Volume L, R, Noise volume L, R, and slave
synthesizer Gate, CV
•Noise generator with associated VCAs and Low Pass Filter
•Headphone Amplifier
2.2 VCA Operation
The VCAs on the MIXER Card are made up of SSM 2024 Quad VCA ICs.
The audio inputs to these VCAs come from the VCF card audio outputs.
Whenever a key is pressed and a voice activated, an ADSR voltage is
generated at the appropriate CD4051 output and drives the VCA for that
voice. This causes the VCA to pass the VCF audio at its input to the
summing amp at its output. The gain is set by a trimmer in line with the
ADSR signal.
The VCA outputs are mixed in four groups of two such that VCA 0 & 1
come from one op amp output, VCA 2 & 3 from another op amp output,
and so on. When the keyboard WHOLE 8 Mode is selected, the output of
sub-mixer 0, 1 is hard panned to one side of the VOYETRA output, while
the output of sub-mixer 6, 7 is hard panned to the other side. The
outputs for 2,3 and 4,5 are panned to be slightly offset from the center of
the stereo spectrum. When the SPLIT or LAYER modes are selected,
the outputs of 0, 1, 2, 3 are hard panned to one output while the 4, 5, 6, 7
outputs are hard panned to the other side. Of course, the MONO output
always contains the sum of all eight voices.
The switching to accomplish this output panning is accomplished by
using a DG308 analog switch that is turned on by a 0, +8V control signal
called SPLIT/WHOLE 8 generated at the DAC CARD.
The L and R output mixers consist of two VCAs that are used to set the
output level and serve as noise gates. When no keys are pressed, the
CPU turns off these VCAs to quiet the system output. The output level is
set by the Master Volume Control on the POT PANEL and the Parameter
trimmers. The CPU digitizes the parameter trimmers and demultiplexes