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SQ-80
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Ensoniq Corporation SQ-80 User's Manual

Inside SQ80 – a technical description
Rainer Buchty
eMail: rainer@buchty.net
http://www.buchty.net
September 29, 1999
Abstract
Since Ensoniq refuses to give any technical information about the SQ80 Cross Wave Synthesizer someone had to do the job... I hope this docu­mentation will help the electronically skilled to repair and/or improve their beloved machine. At least it will give some deeper understanding of what’s going on inside.
Contents
1.1 What is the (E)SQ family of synthesizers all about? . . . . . 6
1.2 Synthesis Parameters . . . . . . . . . . . . . . . . . . . . . . . 6
1.3 The sequencer . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4 Multitimbrality - I need more voices! . . . . . . . . . . . . . . 8
2.1 System Overview . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2 The one which drives it all: MC6809E . . . . . . . . . . . . . 13
2.3 Let there be sound: DOC5503 and CEM3379 . . . . . . . . . 14
2.4 The art of disk storage . . . . . . . . . . . . . . . . . . . . . . 15
2.4.1 Track Layout . . . . . . . . . . . . . . . . . . . . . . . 15
2.4.2 Disk Directory Structure . . . . . . . . . . . . . . . . . 16
2.4.3 Sequencer Memory Dumps . . . . . . . . . . . . . . . 16
2.4.4 Bank Files . . . . . . . . . . . . . . . . . . . . . . . . 17
2.4.5 Program Files . . . . . . . . . . . . . . . . . . . . . . . 17
2.5 What comes in, must come out - the I/O subsystem . . . . . 19
2.6 The system software . . . . . . . . . . . . . . . . . . . . . . . 20
2.6.1 OSRAM . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.6.2 Cartridge . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.6.3 Hidden Functions . . . . . . . . . . . . . . . . . . . . . 20
3.1 General problems . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.2 MIDI mysteries . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.3 Keyboard Trouble . . . . . . . . . . . . . . . . . . . . . . . . 25
3.4 Storage Hassles . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.5 Panel Problems . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.6 Flaky Tape . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2
CONTENTS 3
C.1 WD1770/1772 Floppy Disk Controller / Formatter . . . . . . 41
C.1.1 Description . . . . . . . . . . . . . . . . . . . . . . . . 41
C.1.2 Architecture . . . . . . . . . . . . . . . . . . . . . . . 41
C.1.3 Processor Interface . . . . . . . . . . . . . . . . . . . . 43
C.1.4 General Disk Read Operation . . . . . . . . . . . . . . 45
C.1.5 General Disk Write Operation . . . . . . . . . . . . . 45
C.1.6 Command Description . . . . . . . . . . . . . . . . . . 46
C.1.7 Type 1 Commands . . . . . . . . . . . . . . . . . . . . 48
C.1.8 Type 2 Commands . . . . . . . . . . . . . . . . . . . . 50
C.1.9 Type 3 Commands . . . . . . . . . . . . . . . . . . . . 52
C.1.10 Type 4 Commands . . . . . . . . . . . . . . . . . . . . 54
C.1.11 Status Register . . . . . . . . . . . . . . . . . . . . . . 55
C.1.12 Recommended Layout for 128-Byte Sectors . . . . . . 56
C.1.13 Recommended Layout for 256-Byte Sectors . . . . . . 57
C.1.14 Generic (non-standard) formats . . . . . . . . . . . . . 58
C.2 SSM2300 Octal Sample&Hold . . . . . . . . . . . . . . . . . . 61
C.3 MC/SN 2681 DUART . . . . . . . . . . . . . . . . . . . . . . 63
C.4 CEM3360 Dual VCA . . . . . . . . . . . . . . . . . . . . . . . 89
C.5 CEM3379 Analog Signal Processor . . . . . . . . . . . . . . . 93
C.6 Ensoniq DOC5503 . . . . . . . . . . . . . . . . . . . . . . . . 103
C.6.1 Common Registers . . . . . . . . . . . . . . . . . . . . 103
C.6.2 DOC registers for individual Oscillators . . . . . . . . 103
C.6.3 Wavetable Address Generation . . . . . . . . . . . . . 106
C.6.4 Pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
C.7 MC/HD 68B09E CPU . . . . . . . . . . . . . . . . . . . . . . 109
C.8 AD7524 Analog/Digital Converter . . . . . . . . . . . . . . . 145
4 CONTENTS
Chapter 1
Introduction
The SQ80 was released at the beginning of 1988 (at least here Europe) and was one of the first so-called workstations. It not only was a synthesizer but also came along with a 8-track sequencer. Obviously, it also featured multi-timbrality and dynamic voice allocation which was quite a novum. And as one of the first synthesizers it was equipped with a 3.5” disk drive
- no need for expensive sound cartridges or excessive bulk dump sessions anymore.
What also made the (E)SQ family of synthesizers a success was the
Unfortunately, the early Ensoniq synths and accessories for these such
T M
synthesizer – the VFX – hit the market.
5
6 CHAPTER 1. INTRODUCTION
OSC #1
OSC #2
OSC #3
DCA #1
DCA #2
DCA #3
VCF VCA/PAN
LFO #2LFO #1 LFO #3
EG #1 EG #2 EG #3 EG #4
Sync
AM
1.1 What is the (E)SQ family of synthesizers all about?
• bigger waveform memory (75 waves including the 32 ESQ-1 waves)
• bigger sequencer memory (64kB by default)
• built-in 3.5” disk drive
• keyboard with polyphonic aftertouch
What makes the (E)SQ synthesizers (even today!) quite interesting is their great flexibility. They can either sound warm and analog but also cold and digital. The reason lies in their hybrid nature – digital oscillators but analog sound processing. The factory presets give a rough overview over the SQ80’s capabilies but to get a real impression of what this machine can do should get e.g. the Transoniq Hacker patches.
1.2 Synthesis Parameters
Figure 1.1 shows the basic architecture of each voice:
Figure 1.1: Architecture of an SQ80 voice
1.2. SYNTHESIS PARAMETERS 7
Unlike modern synthesizers where a single voice mostly consists of an oscillator plus filters the SQ80 offers 3 oscillators per voice (using 4 oscillators might have overextended the CPU’s capabilities, I just don’t know) which gives it a rich base sound. Also pretty nice is that per voice four envelope generators and three LFOs exist – soundprogrammer’s heaven. Besides, the SQ80 offers some more features which I will explain as follows:
Gated Mode: Besides some one-shot (not loopable) waveforms the SQ80
offers a special playback mode where an Envelope is only processed once treating the sustain level as just an ordinary envelope step. This is nice for producing percussive sounds which don’t need a sustain phase.
Synchronization: You know that fancy “EEEOOOOW” sounds? It’s the
audible effect of one oscillator synchronizing another. The SQ80 can produce these, too, since the DOC chip supports oscillator synchro­nization - unfortunately only between an even/odd pair of oscillators, that’s why only synchronizing OSC2 by OSC1 is possible.
Amplitude Modulation: Good for making gong sounds or any other
which need disharmonic spectrals. Not quite the same as ring modu­lation but pretty close.
Oscillator Restart In usual DCO-based synthesizers the oscillator starts
playing back a wave from its very beginning when a key is played. This is ok for complex waves but results in a static sound when using short, looped waves such as e.g. SAW. Thinking of analog oscillators such a reset of the waveform is unnatural (saw oscillators are based on integrators) - the SQ80 offers both: oscillator reset or free-running waves. However, this can be only programmed per sound program, not individual for each oscillator.
LFO Specialties: Instead of a fixed output amplitude the modula-
tion depth of each LFO can be programmed to fade in (or out). If that’s not enough an assignable modulation depth modulator exists.
Digitally controlled synthesizers tend to offer very static LFOs: As soon as you hit a key the LFO starts at position 0 of the selected wave
- this is very annoying when using the LFO for e.g. filter sweeps, so the SQ80’s LFOs can be programmed to be running freely or being reset by each keystroke. And if you think that digital LFOs sound too static – switch on the HUMANIZE function!
Envelope Specialties: Not much uncommon here, but for completeness’
sake I’d mention that an envelope generator can be programmed
8 CHAPTER 1. INTRODUCTION
to react on key velocity (linear and exponential response) and key position. What’s really fancy about the envelopes is that the so called second release which does not really replace a reverb but produces a similar effect.
Of course the envelopes are not of ADSR-type but a 4 level/rate model.
1.3 The sequencer
On the “minus” side there’s only few. Have you ever tried to attach a new volume level to an existing track after having recorded it? On earlier software versions this is impossible.
1.4 Multitimbrality - I need more voices!
Unfortunately, the SQ80 offers only 8 voices which is not much if you think of complex arrangements. Fortunately, it has a really neat voice allocation algorithm (much better as the very static one used e.g. in the Yamaha SY-77) which can be influenced per sound program individually. Think of natural instruments - if you play the same note twice the previously played note will be replaced by the following one. The SQ80 can mimic this behaviour – or disregard nature, just as you like. But keep in mind that the latter one forces a more aggressive voice allocation since there’s no oscillator to “recycle”.
Lucky people (such as me :-) own more than one SQ80 – and can easily daisy-chain these by enabling the overflow mode. This means that any note
1.4. MULTITIMBRALITY - I NEED MORE VOICES! 9
10 CHAPTER 1. INTRODUCTION
Chapter 2
Technical Documentation
1. “The schematics are proprietary and not meant to be given away.” (This was after my naive(?) first-time asking, but hey, I got the schematics of my Yamaha equipment aswell - and these are far more high-tech!)
2. “Your work sounds incredible – but we wish you all the best.” (after telling them that I started to reverse-engineer the SQ80)
3. “Congratulations on your work!” (when finally telling them that I succeeded in drawing schematics, documenting the OS and creating an assembly language source code for further OS development)
With no word they told me that they dislike these efforts, neither they
told me to keep that knowledge for myself. So here it comes...
11
12 CHAPTER 2. TECHNICAL DOCUMENTATION
Sequencer Memory
DOS Memory
Operating System
System Memory
CPU
DUART
Cart. MIDI
Keybrd.
&
Displ.
Control
Address Decodier
Floppy
Drive
DOC
FDC
2.1 System Overview
Basically, the SQ80 is nothing more than a microcomputer with some spe­cialized peripherals. Figure 2.1 gives an overview over the system architec­ture:
Figure 2.1: Anatomy of an SQ80
Mostly computer stuff, the only dedicated “musical” parts are the DOC and the analog sound processors. This is a big advantage over other, es­pecially modern synthesizers, since you can get replacement parts from the next distributor of electronic parts.
2.2. THE ONE WHICH DRIVES IT ALL: MC6809E 13
2.2 The one which drives it all: MC6809E
What made the 6809 that attractive was its computing power combined with a very flexible instruction set. The SQ80 makes heavy use of the 6809’s specialties:
• loadable system stack pointer S (used for context switching)
• loadable user stack pointer U (used as another 16-bit index register)
• 16-bit index registers X and Y
• 16-bit accumulator D
• fast (integer) multiplication / division
• software interrupts (used for error signalling)
• SYNC and CWAI commands forcing the CPU to wait for an external
interrupt
In the SQ80 the 6809E was used. Unlike the 6809 it’s E–mate could be completely externally controlled which is needed inside the SQ80 where the generation of clock signals is influenced by the DOC chip. See p.111 for details on this processor.
14 CHAPTER 2. TECHNICAL DOCUMENTATION
2.3 Let there be sound: DOC5503 and CEM3379
Some of you might know that the creator of the DOC, Bob Yannes, was also the designer of the all famous SID chip which was the sound engine of the Commodore 64 home computer. Both are based on the same principle: phase accumulation. This means that the frequency of a digital voice is not determined by the playback frequency (clock) as it was used in former drum computers (and which will drive every today’s studio technician mad since a variable playback frequency won’t fit very well into digital mastering using fixed frequencies of 44.1kHz or 96kHz), instead the frequency will be derived from a counter: This counter – roughly said – counts up the waveform address. If you need to get higher frequencies you increment the counter steps, for lower frequencies you decrement them. Thus the name “phase accumulator” – it’s an accumulator where the resulting address is a phase pointer.
The DOC uses a 24bit counter for this purpose. The frequency­determining value will be added to the lower 16 bit whereas the higher bits are used as the phase pointer (which of them will be used can be programmed, see 107 for details).
The DOC contains 32 digital oscillators and 32 amplifiers aswell as an output multiplexer to make it possible to route these 32 oscillators to one out of 16 channels. The SQ80 makes only use of 24 oscillators/amplifiers and 8 channels. The uppermost channel mux bit is used for selecting either Wave ROM 0 or 1.
Now the CEM3379: It was designed by Curtis Electromusic and con­tains an analog 4pole low-pass filter with adjustable center frequency and resonance. Furthermore it also contains a dual VCA with adjustable gain and pan position. Each SQ80 voice contains mainly of one CEM3379, the DOC’s output is routed to the desired CEM3379 using an ordinary 4051 multiplexer.
2.4. THE ART OF DISK STORAGE 15
2.4 The art of disk storage
The SQ80 uses standard 3.5” DD disks for storage of programs, program banks and sequencer data. As disk controller it uses the Western Digital WD1772 which was quite common in the 80s, the same chip is used e.g. inside the Atari ST machines and the Commodore 1581 disk drive.
The disks have a fixed geometry: Although one disk may hold up to 880kB of data it’s not possible to make dynamic use of a disk in a way of storing e.g. up to 220 program banks or up to 8834 single programs. Neither it is possible to store more than 10 sequencer files even if they don’t make use of the entire disk. Instead the fixed disk geometry causes the well known layout of 10 sequencer/sysex files, 40 program banks and 128 single programs – which unfortunately most of the time is just wasting disk space.
2.4.1 Track Layout
Some of you might have tested it: It’s almost impossible to copy a SQ80 disk using standard PC drives. This is due to the fact that Ensoniq – in their eternal wisdom – decided to use a very special disk format. Not only that they use a fixed disk layout (which is understandable in terms of complexity: A fixed disk layout is just way easier to program and needs less administration – on the other hand it wouldn’t have been a big problem to modify the SQ80 hardware to have additional ROM space which would be needed for the implementation of a “real” DOS making dynamic use of the disk space), they also use a special track/sector layout:
• sectors 0 to 4 hold 1024 data bytes each
• sector 5 holds 512 data bytes
The reason why a lot of PC disk controllers fail to read and even write these disks is the change in sector size inside a track. Whereas the WD177x family can perform single sector reads and writes older PC floppy controllers such as the NEC 765 or Intel 8278 based ones can only read and write a single track. More modern ones like Intel 82077 and newer are at least able to read and write single sectors – but not format these individually.
Have you ever wondered why the SQ80 won’t format a disk where your PC formats it without bad sectors? That’s because Ensoniq formats DD disks to their limit (880kB / 901120 bytes) – which also made the Commodore Amiga be very sensitive to cheapo disks. (Mean trick: Let the SQ80 format and complain, then put the disk into your PC and copy disk images using the SQ80 Toolkit onto it.
16 CHAPTER 2. TECHNICAL DOCUMENTATION
2.4.2 Disk Directory Structure
The disk directory consists of two parts: The first part is responsible for “big files”, namely sequencer memory dumps and sound banks. Thus, it holds 50 entries of the following structure:
typedef struct directory_entry {
char type; char name[10]; int size;
} de_t;
Size and type are only vital for sequencer files since they tell, guess
what... File size is measured in bytes, but the file type needs some more explanation:
/* standard file types */ #define FREE 0 /* unused */ #define OS 1 /* operating system */ #define BNK 2 /* program bank */ #define SNG 3 /* all sequence (song) */ #define SEQ 4 /* one sequence */ #define SYX 5 /* system exclusive */ #define PRG 6 /* single program */
I guess you get it from the above table. The very first entry is used for unused or deleted file, the second one is not used on the SQ80 and is a remnant of the good old Mirage times - it’s reserved for bootable system files.
But what about the single program files? It’s definitely not true that
you need to extract the program names from a program files PCB structure
- if that would be the case you’d hear annoying floppy noises each time you access the DISK/LOAD/PROGRAM menu. Instead, the file names are listed just behind that 50 “big” entries.
2.4.3 Sequencer Memory Dumps
This kind of files occupies the first and biggest disk partition, you will find these at the following locations (format: start c/h/s, end c/h/s):
{ 0,0,0, 6,0,3}, /* seqram #1 */ { 6,0,4,12,1,2}, /* seqram #2 */ {12,0x11,3,19,1,1}, /* seqram #3 */ {19,1,2,25,0,0}, /* seqram #4 */ {25,0x10,1,31,0,4}, /* seqram #5 */
2.4. THE ART OF DISK STORAGE 17
{32,0,0,38,0,3}, /* seqram #6 */ {38,0,4,44,1,2}, /* seqram #7 */ {44,0x11,3,51,1,1}, /* seqram #8 */ {57,1,2,57,0,0}, /* seqram #9 */ {57,0x10,1,63,0,4}, /* seqram #10 */
Looks easy? It indeed is - but not as simple as it looks like. Your SQ80 is a lazy guy which changes disk sides only when it’s necessary. This means a multi-track read goes like this: c/0 – c/1 – c+1/1 – c+1/0 – c+2/0 and so on. To mark whether the head has changed before or not bit 4 of the head byte is used - if it is set to 1 it forces a head change together with the next track change.
But there’s even more: On sector 5 of the end track/side there’s addi­tional information stored such as song names. You’ll see the side effects of this when discussing the storage of single program files.
2.4.4 Bank Files
In the directory structure these files are marked with file type 2 (BNK) and size 0.
2.4.5 Program Files
geo_t *get_prog_pos(geo_t *prgpos, int pnum) {
switch( ((pnum-1)&64)|(((pnum-1)&63)+2) ) {
case 0x06: prgpos->st=0x42;
prgpos->sh=0; break;
case 0x19: prgpos->st=0x42;
prgpos->sh=1; break;
case 0x1f: prgpos->st=0x43;
prgpos->sh=1; break;
case 0x39: prgpos->st=0x44;
prgpos->sh=0; break;
case 0x3f: prgpos->st=0x44;
18 CHAPTER 2. TECHNICAL DOCUMENTATION
prgpos->sh=1; break;
case 0x53: prgpos->st=0x45;
prgpos->sh=1; break;
case 0x6c: prgpos->st=0x46;
prgpos->sh=0; break;
case 0x73: prgpos->st=0x46;
prgpos->sh=1; break;
default: prgpos->st=((pnum-1)&63)+2;
prgpos->sh=((pnum-1)&64)>>6;
break; } prgpos->ss=5; prgpos->et=prgpos->st; prgpos->eh=prgpos->sh; prgpos->es=prgpos->ss; return prgpos;
}
Needless to say that the storage format – again – is PCB.
2.5. WHAT COMES IN, MUST COME OUT - THE I/O SUBSYSTEM19
2.5 What comes in, must come out - the I/O sub­system
Big words for a small chip - but indeed the MC2681 DUART is a vital part of any SQ80 since it’s responsible for the following functions:
• MIDI communication (Serial Port A)
• communication with keyboard processor (Serial Port B)
• communication with panel processor (Serial Port B)
• tape I/O
• cartridge presence checking
• disk head access
• disk change detection
• selection of voltages to be sampled
• OSROM low bank switching
• SEQRAM selection and bank switching
• metronome click generation
• timing
To be more precise, the input and output lines are used for the following
tasks:
Inport Task Outport Task
0 Tape In 0 Disk Head 1 Disk Change Detection 1 Multiplexer Bit 0 2 Cartridge Detection 2 Multiplexer Bit 1 3 500Hz Interrupt 3 Multiplexer Bit 2 4 500Hz Interrupt 4 Metronome Click Generation 5 1kHz Interrupt 5 Metronome Click Generation 6 1kHz Interrupt 6 Tape Out
- 7 Tape Out
Table 2.1: Additional DUART tasks
20 CHAPTER 2. TECHNICAL DOCUMENTATION
2.6 The system software
2.6.1 OSRAM
2.6.2 Cartridge
0x3FFD: set to 0 if cartridge bank B contains data, 0xff else
0x3FFE: set to 0 if cartridge bank A contains data, 0xff else
0x3FFF: set to 0x01 if cartridge contains program banks, it’s also possible
to take over the system if 0x55 is stored here.
If a cartridge is present or not is detected by the DUART’s input port
2.
2.6.3 Hidden Functions
COMPARE
Analog Voltage Check
FILTER
With this function the SQ80 recalibrates its filters. This is to ensure that all 8 voices have (nearly) the same filter response parameters ­unfortunately, this tuning is responsible for the SQ80’s filter not being able to self oscillate: The filter tuning parameters are calculated in a way that self-oscillation is just impossible.
2.6. THE SYSTEM SOFTWARE 21
MASTER
Prints the OS version. The latest version released by Ensoniq was 1.8, unfortunately there’s no official support anymore but if you are able to program EPROMs yourself you’ll find the images on my web page.
MODES
If you ever wondered who built the SQ80 call this menu.
Soft Button 1
Reinitialization (“OSRAM Formatting”) - as mentioned above this function is needed after an OSROM upgrade.
Soft Button 6
Warm Reset. Nice idea, but jams the machine - at least on OS versions
1.7 and 1.8.
SPLIT/LAYER
Keyboard recalibration.
22 CHAPTER 2. TECHNICAL DOCUMENTATION
Chapter 3
Troubleshooting
Almost all eMails I get concerning the SQ80 are about the synthesizer be­having strange or not working at all. On the following pages you’ll find hints about what might cause misbehaviour and how to fix it.
23
24 CHAPTER 3. TROUBLESHOOTING
3.1 General problems
The system won’t come up...
If your SQ80 does not come up at all, showing a blank display and no reaction to any MIDI message or key pressure its most likely the power supply. Check for blown fuses or dried-out capacitors. If that’s not the problem replace U6 and/or U10.
I’ve upgraded the OS and now the system doesn‘t come up!
Just press RECORD together with soft button 1 (the upper left above the display). This will perform a complete reset including reformatting the OSRAM. Afterwards, everything should be ok again. If not check the OSROMs for correct placement.
Display says that the battery voltage is low.
Just replace it. Any 3V to 5V lithium battery will be fine. If you don’t find the battery on the motherboard you should probably leave that step to somebody who knows on which side the soldering iron heats...
The pedal won’t work.
Check cabling. Otherwise replace U33 – if that doesn’t help either your DOC is f*cked up, try to get one from a used/dead Apple IIGS, ESQ-1 or SQ80. Or send it to me so that I can make an expander version out of it.
The wheels won’t work.
Check pedal cabling. Rest see above.
My cartridge isn’t recognized.
Check if cartridge is formatted. Check cabling. Check presence of 5V at pin x of U6 while cartridge is inserted. Voltage found? Build a new cable using new connectors. If that won’t help replace U6. If you did not find the voltage replace U2 to U4.
There are no metronome clicks anymore.
Replace U39. If that doesn’t help replace U44. If that didn’t help either replace U6.
I can’t hear anything.
Check pins 6 and 9 of U44 if it gets any signals. If this is not the case replace U39, otherwise replace U44.
Some voices are missing.
Check pin 8 of U40-43, U45-48 playing an 8-note chord. If one or more doesn’t get an input signal replace U36. If that doesn’t help search for a new DOC and replace U27.
3.2. MIDI MYSTERIES 25
The voices are stuck!
Check sustain switch. Replace U33.
The sustain switch doesn’t work.
See above.
The pedal doesn’t work.
Check pedal. Replace U33.
The Sequencer switch doesn’t work.
Check switch. Replace U33.
If they all get input signals identify the one which does not output a signal on pin 15 and 17 (be sure to have pan set to 8 with no modu­lation while testing this) and replace it.
3.2 MIDI mysteries
I can’t send MIDI messages, but receiving them is fine.
Replace Q1 to Q4. If that doesn’t help, replace U6.
I can’t receive MIDI messages,but sending them is fine.
Replace U12. If that doesn‘t help, replace U6.
I can only receive/send some MIDI messages.
Duh! Go to MIDI menu and enable the desired messages.
3.3 Keyboard Trouble
During reset display says keyboard is disabled!?
Check cabling. Power the system on and check U6 pin 10 and 11 for serial communication. If you don’t see anything at pin 10 replace U1 (68HC11) on the keyboard PCB – otherwise replace U6.
I get keyboard processor errors.
Check cabling. Replace U1 (68HC11) on the keyboard PCB. If that doesn’t help replace U6.
Keyboard calibration fails all the time.
Check cabling. If that doesn‘t help try to get a new keyboard ASIC or send the SQ80 to me to make a nice expander version out of it.
The SQ80 won’t leave keyboard calibration.
Check cabling. Check keyboard PCB for cold soldering spots. Check serial communication (see above).
My keyboard doesn’t work – but I get no error message!
Duh! Go to MASTER menu and enable it.
26 CHAPTER 3. TROUBLESHOOTING
3.4 Storage Hassles
I get more and more read/write errors.
Clean the drive using an ordinary cleaning diskette – or be tough and clean the drive heads using Q-tips and isopropanole. If that won’t help replace the drive. Any 720kB drive with shugart bus will do the job.
The drive doesn’t show any reaction.
Check cabling. Replace U24 and U29. If that won’t help, replace U9.
3.5 Panel Problems
I can’t see anything...
Check cabling. Check for correct display voltage. If that’s not the problem check/replace the display drivers. If that won‘t help, send the SQ80 to me to make a nice expander version from it since either the display itself or the panel CPU is broken. No replacement possible.
Some keys won’t work.
Remove the panel PCB and clean the contacts.
Some keys are stuck.
Remove the panel and clean the keys / holes.
3.6 Flaky Tape
I can’t load from tape.
Replace U25. If that doesn’t help replace U6.
I can’t sync in.
see above
I can’t write to tape.
Replace U6.
I can’t sync out.
see above
Appendix A
Parts List
# Type Description Task
Q1 2N3906 MIDI out Q2 2N3904 MIDI thru Q3 2N3906 MIDI thru Q4 2N3906 MIDI out Q6 JE182 Amplification Q7 Amplification U1 74LS04 hex inverter U2 74ALS245 8x bidir. buffer/driver Cartridge Data U3 74ALS244 8x buffer/driver Cartridge Address/Control U4 74ALS244 8x buffer/driver Cartridge Address/Control U5 74LS161 4bit counter Timer U6 MC2681, SCN2681 DUART Communication & Control U7 74LS10 3x 3-input NAND misc. Cartridge U8 74LS00 4x 2-input NAND Clock Generation U9 WD1772 FDC Disk Drive Control U10 MC6809E CPU Central Processing Unit U11 74LS74 2x D-type FF Q-Clock Generation U12 6N138 opto coupler MIDI in U13 74F139 2x 2-to-4 mux Address Decoding U14 4364-15 SRAM 8kx8 OSRAM U15 74F139 2x 2-to-4 mux Address Decoding U16 27C256-20 EPROM 32kx8 OSROM high U17 74LS244 8x buffer/driver DOC Addressing U18 4364-15 SRAM 8kx8 DOSRAM U19 74F139 2x 2-to-4 mux Address Decoding
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28 APPENDIX A. PARTS LIST
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# Type Description Task
U20 27C256-20 EPROM 32kx8 OSROM low U21 74LS245 8x bidir. buffer/driver DOC Data U22 27C512 EPROM 64kx8 WAVE 0 U23 27C512 EPROM 64kx8 WAVE 1 U24 7406 hex inverter Signal Driver (to Floppy) U25 LM311 voltage comparator Tape Input U26 74LS373 octal latch Wave Address Demultiplexing U27 DOC5503 ASIC Sound Generation, A/D Conversion U28 74LS377 octal latch Analog Parts Addressing U29 AD7524 DAC CV Generator U30 TL081 OPAMP CV amplification U31 MC34085 OPAMP Sound Amplifier U32 TL081 OPAMP Volume Adjustment U33 4051 1-to-8 analog mux Voltage Multiplexer (for ADC) U34 SSM2300 8x sample & hold ENV4 CV mux U35 SSM2300 8x sample & hold Q CV mux U36 4051 1-to-8 analog mux Audio Router U37 SSM2300 8x sample & hold PAN CV mux U38 SSM2300 8x sample & hold FF VC mux U39 TL084 4x OPAMP Audio L/R U40-U43 CEM3379 analog voice processor Filter / DCA4 / PAN U44 CEM3360 dual VCA final amplifier U45-U48 CEM3379 analog voice processor Filter / DCA4 / PAN U49 74LS05 hex inverters Floppy Driver U50 43256C-12 SRAM 32kx8 SEQRAM low U51 43256C-12 SRAM 32kx8 SEQRAM high U52 74LS138 3-to-8 mux SEQRAM select U53 74LS74 2x D-type FF Mapper U54 27C512 EPROM 64kx8 WAVE 2 (not installed) U55 27C512 EPROM 64kx8 WAVE 3 (not installed) Y1 OSC8MHz Quartz Oscillator System Clock Generator
Table A.1: Parts list
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