EEH DS 500 Sequencer

EEH DS 500

Overview This is a possible project to recreate a very rare and unusual early digital sequencer the EEH DS 500. Only a handful were manufactured in 1981/82 in Germany and used by Tangerine Dream and Klaus Schulze, rather briefly as they quickly adopted MIDI sequencers in 1983.

I came across the sequencer in May 2020 and the web pages by  Till Kooper here, which has bote the schematics and a German user manual. I have translated and improved the user manual into English and its here.

EEH DS 500 Opeartions Manual (English)

Looking at the schematics and after locating the OS EPROM binary I realised I could recreate the DS 500 completely. Whilst the sequencer is hard to program and has only 500 notes, it does have loops within loops, and makes an interesting project during the 2020 Covid-19 lockdown.

Technology Whilst the technology used in the DS 500 is 40 years old, the IC’s are still available at a low cost expect the DAC and unusual SN4929 combined NAND and Inverter CMOS chip, which are harder to locate and more expensive.

  • NEC D780C (Z80 microprocessor) £4.50
  • Intel 2716 EPROM (2KB)
  • Two NEC D444C SRAM 450ns £7.00
  • Intel P8225A £3.50
  • Ferranti ZN426E DAC £20+
  • 74LS48 and 74LS145 £3 each
  • SN4929N
  • CMOS 4016, 4030, 4011 , low cost
  • LM324 replace with low drift OP2277 Op Amps
  • DL304 7-segment displays  £7.50

Switches & Buttons The original Rafi PPG style switches and buttoms are no longer manufactured. The closest match is from Marquadt and the 6425 series of momentary switches. These have 16mm sqaure caps in different coloures, lettering and with space for a LED. After lots of research I gave up on finding every numeric key cap (7 was not in stock) and went with the correct light grey, dark grey and black cap colours with a red start/stop button. I will label the numerics and button descriptions onto the front panel.

Here is the BOM:

  • 2x Switch Body Red LED –  6425.4111
  • 4x Switch Body Yellow LED –  6425.4121
  • 4x Switch Body Green LED –  6425.4131
  • 10x Switch Body no LED –  6425.1101
  • 2x Red button with LED – 826.000.071
  • 8x Dark Grey button with LED – 826.000.021
  • 10x Light Grey buttons without LED – 826.000.031

EEH CM-4

Project Status PCB design stage as at 16 May 2020.

EEH CM4 This is a much more powerful digital sequencer that was used by Tangerne Dream in the Poland concerts, with 4-tracks and 16 steps. Five units were made around 1983. The CM4 lives in an 8U 19″ rack panel and has the following features:

  • 4x CV and Gate Outputs
  • Clock in and out
  • Clock divider switch
  • MIDI out
  • 40 memories (+ panel memory)
  • Patterns can be linked to songs.
  • Per track: display, end of sequence programming (reset value), note / pause ratio.
  • Quantization of notes.
  • Per step: potentiometer for programming the CV/gate values, switch with LED for switching the gates on and off.

EEH CM4 Close Up

It was based on the same Z80 technology used in the DS 500, but with more RAM (6 KB) and additional displays and front panel key pad controls. A coupld of 16-way multiplexers and two 8225 Programmable Periperal Interface chips are needed for all the I/O. A different DAC was used maybe a Burr Brown PCM54. The connections are at the base of the front panel, where you can see the CV and Gate outputs as well as MIDI, which presumably is just MIDI clock out, maybe clock in.

The usual PPG style Rafi push button switches with inbuilt LED’s are visible throughout, a total of 32. Unfortunately the CM4 must have been just as difficult to programme via a numeric key pad as the DS 500 and soon obsoleted by MIDI computers and seqeuncers. Tangerine Dream sold there two probably in 1984 and as least one still exists today.

Information and images courtesy of Mirko Luethge August 2002 and Carsten Werner 2005.

Roland MC500 Refurb

MC-500 As Bought

Overview I bought an original 1986 MC-500 in May 2020 for a nice low price but sold as a repair job. It turns out to be in very good condition and the issue was a damaged OS floppy diskette, which refused to boot and gave I/O ERROR 3. Once I had powered it up with a brand new DS/DD diskette with Super MRC-500 software it works perfectly. The LCD had faded after 35 years and needs an OLED replacement and the diskete drive is rather loud and clunky but I will keep it until it fails.

Old LCD Display

The MC-500 was way out my budget in 1986 at £999 and I bought an Atari 520STFM (£299) in 1987 and used it with MasterTracks Pro for many years until it was struck by lighting one night and exploded.

I had added a 20MB hard disk to the Atari to enable a large collection of songs to be built up. The price of hardware sequencers has of course fallen significantly, so I can now experience and use this approach in the Garden Studio.

New OLED Display

OLED Display This is an easy plug and play replacement using the Newhaven 2×20 NHD-0220D2W-ABJ, which is a nice blue on black OLED. The EL backlight connections are not needed and can be removed along with the EL transformer, which is on the PSU PCB.

My trannsformer has a slight wine so I removed R1 and R2 from the PCB to cut the power to the transformer, which avoided the need to take the PCB out. The display is hand wired to the 14-way cabling rather than using a plug and socket. I removed the old LCD from its metal frame and then carefully peeled the metal frame from the display bezel which has some doubled sided tape.

Diskette Drive The drive works ok and uses 3.5″ DS/DD diskettes which are a bit expensive to buy these days. The sensible approach is to install a Gotek drive but I rather like using floppy diskettes as I can write stuff on the label about the song. So whilst the drive still works I will keep it in place. I also have a MC-300 and MC-50, so I can swap songs between them.

Power Supply Recap I decided against a recap of the power supply, as the main electroytic caps were in good condition and it meant quite a bit of dismantling and desoldering cables. In the future I will do a full power supply refurb along with the regulators, but for now no changes, If you do want to replace them us high quality Panasonic EEU-FC’s with the same diameter and height:

  • 4700uF 16V – EEU-FC1C472SB
  • 2200uF 25V – EEU-FC1E222SB

Power Supply

Technology The MC-500 is based around an enhanced Z80 micro processor manufactured by Hitachi as the HD64180 with integrated memory management and on chip peripherals. It was launched in 1985 and initially Roland used the DIP64 pin version the R0, before moving onto the 80-pin SMD R1 version for the MC-500 Mark II launched in January 1988. The R0 DIP version can only address a maximum of 512KB, with just 256KB fitted in the MC-500 using 8x 32KB RAM chips.

The MC-500 Mk II uses the R1 micro processor which can address 1 MB of RAM, with 756 KB fitted, and the subsequent MC-50 and MC-50 Mk II also use the same microprocessor giving the this micro composer a life span of nearly ten years. The MC-50 versions use onboard memory for the OS to live in, so its faster to use and boot, but not as classic in style!

Memory Upgrade My MC-500 was manufactured in July 1986 only a few months after the launch in January, and it uses the original PCB layout with 256 KB of RAM and the R0 version of the HD64180 which has 19 addresss lines. This limitation means the early MC-500’s can not be easily upgraded to 786 KB of memory. The processor and RAM need swapping out and the extra address line added. Roland did offer the OM-500 upgrade, which must be a main PCB swap, and the resulting sequencer is called a MC-500B by Roland..

MRB-500 Software

Software Options & Versions In 1986 the MC-500 was launched with an initail software release (MRC-500) which was upgraded with more detailed features as Super MRC in 1988 along with a wider range of software to enable SysEx storage, chained songs for live performance, MIDI file conversion and a set of rthymn tracks. Here are the various software releases, click on the titles to download the .OUT file:

MC-500 like new

I use the MRB-500 to store MKS-80 Patch Banks as it perfroms the correct handshake and MRM-500 to transfer MIDI files to Cubase and back.

Recreating the Software The MRP and MRB software cannot be downloaded from Roland and the original boxed software is expensive at £50 – 100, when you can find it secondhand. Fortunately 20 years ago R. Kevin Grannum archived the files onto his web site in .DAT format using obscure uCopy software. The web page exists but the links are all broken, but with Wayback Machine I found the files and downloaded them.

With some careful hex editing and byte level compaisons I was able to trim the start of the files and add extra bytes at the end to make them into binary 720 KB files in .OUT format that SDISK (or WDISK) can write to a 3.5″ DS/DD floppy diskette. The diskette must be pre-formatted by the MC-300/500/50.

Alesis DataDisk Refurb

Alesis DataDisk

Overview I picked up an Alesis DataDisk in May 2020 for £25, so I  can store and retrieve SysEx data from my hardware synths rather than having to power the computer on and use software. The 1U rack  connects up to my MIDI hub and uses a 3.5″ floppy diskette to store 800 KB of data.

The DataDisk was launched in late 1989 at a rather steep £299, but was quite popular for musicians touring and wanting to restore all their patches across multiple synthesizers. In the studio an Atari 520 was more effective with the right software, and that is what I used in 1990. The high cost of the DataDisk put me off buying one, until now!

Recap Complete

Refurb The DataDisk looks like an x-hire unit; connections have been hot glued and there is lots of wear to the casing and buttons. All the casing screws needed replacing with new ones, and the LCD mount has broken. It also needed a 9V external power supply, which is the same as used with the Quadraverb with a 4-pin plug, bought from eBay. I replaced the 16×2 LCD with a new OLED display and glued the mounting back together (two parts were broken) and unglued the ribbon cable.

The original LCD is 16×2 characters with 14 pins, here is the Quadraverb schematic which uses the same LCD. Note that there is no contrast potentiometer but a fixed contrast voltage of -0.6V at Pin 3. Pin 2 is the main GND connection and pin 5 is set low to enable write to the display. Pin 4 is the mode control for either data or an instruction and Pin 1 the +5V.

New OLED Display

I have fitted a new blue character OLED display, the Winstar WEH001602DBPP5BN which is available from Rapid Electronics. It has the same 14-pin connector and PCB size and is a drop in fit as Pin 3 is Not Connected. There is no contrast needed on an OLED display. To be extra safe the cable to pin 3 can be cut or the diode and resistor removed from the main PCB.  The new OLED fits on the same plastic mount but is thinner than the original and therefore the front of the OLED is set back 5mm from the bezel.

The three large 4700uF 25V axial electrolytic capacitors were replaced in the power supply along with 3x 4.7uF 50V and one 100uF 16V capacitor. The OS is 2.10 and does not need upgrading. There was no floppy drive in the unit, so I tried my spare diskette drive but it was not compatible, and I don’t want to hack one. There is not much space in the case left free for the diskette cable at the rear of the drive but there is plenty of room for a Gotek drive.

In the Studio I use the DataDisk with my MIDI polysynths to save and restore patch banks; the Wavestation, OB-6, XTk and D-05 using the iConnectivity MIO as the MIDI hub. All these synthesizers can initiate a SysEx dump of patch data, which the DataDisk simply listens for and then reads the data stream and puts it on the diskette. The DataDisk cannot handshake with my MKS-80, so I use the my MC-300 with the MFB-500 Bulk Librarian software which works perfectly.

The DataDisk can also initiate a SysEx Dump request, provided the Manufacturer and Device ID’s are known by the DataDisk software. You simply select these two parameters from the display, however the OS has not had an update for 30 years, and there is no free form editing of the Device ID which would be very useful – see below.

Storage Limitations the DataDisk is limited to 764 KB of patch data storage and a maximum of 53 files. In 1991 the storage limitation was not significant (a D-50 Patch Bank is 36 KB, the Wavestation is 64 KB and the XTk is 70 KB) but today synthesizers can generate much larger SysEx files, such as the OB-6 at 576 KB! Large SysEx files generated by fast PC’s may overwhelm the old synth processors, so I use pauses when sending to the Wavestation. The DataDisk uses a slow processor my today’s standards and therefore should not overwhelm the synths with SysEx, but maybe new synths will overwhelm the DataDisk, we will see!

Gotek Drive Setup It is easy to fit a Gotek drive and here is the setup, you need to customize the firmware:

  • Track Type: MFM, Two sides floppy, GAP3 auto GAP3
  • 80 Tracks, Sector IC Start: 1, Sectors size: 1024, 5 sectors per track
  • RPM: 300,  Bitrate: 250,000, Total sector: 800, Total size: 819200
  • HFE file interface mode: Auto (IBM PC 720kB)
  • Shugart device
  • Hardware Jumper settings: MO and ID0

File Naming The DataDisk reads the inbound MIDI SysEx message and extracts both the Manufacturer and Product ID’s. The Manufacturer ID is either one or three bytes with the DataDisk capable of recognizing the big manufacturers from the 1980’s using a single byte;

  • Sequential 01H
  • Roland is 41H
  • Korg is 42H
  • Waldorf is 3EH
  • Behringer is 00H 20H 32H

The DataDisk is over 25 years old and therefore has not kept up with more recently issued manufacturer ID’s in its ROM based look up table> If the manufacturer ID is not recognized the default is xxH. The Device ID’s are also a problem, as these single byte numbers correspond to a product name which the manufacturer has determined. Once again a look up table is needed and the DataDisk is stuck in 1991!

The DataDisk names the files with 3 set of characters:

  • XXXXXX is the manufacturers name
  • YYYYYY is the product model name
  • ZZZZZZZZ is the name of the file and can be edited

I may extract the ROM code and do an update if there is room in the ROM.

SQ Display

SQ Upgrade Alesis updated the DataDisk to a new SQ model in the Autumn of 1990 with a new firmware version 2.0 (and higher price of £349). SQ stands for SeQuencer as the upgrade enables the DataDisk to record and playback MIDI sequences, with the usual store and retrieval to floppy disk using DS/DD diskettes. MIDI sequences from a keyboard or a MIDI sequencer (like my Roland MC-300) can be recorded and then played back locked to the MIDI clock.

Sequence recording also allows SysEx to be recorded and played back with pauses, which is often how long data streams are managed.  MIDI data is recorded and played back in real time from the diskette with no copying to internal RAM, so there is no lag between hitting MIDI start and the notes being generated, this made the DataDisk as an attractive MIDI song player for live bands.

Buttons These are touch sensitive (multi-speed) versions and not the usual single click momentary buttons, therefore the best I can do is clean the surface of the buttons, and even polish them, but the damaged ones remained pale. A common issue with these buttons after 30 years of UV light.

Inside the DataDisk

Technical Bits  The DataDisk is based on an Intel 8031 microprocessor running at 12 MHz which does all the MIDI handling, front panel scanning and disk access work. It loads the OS from a 27C256 EPROM (32 KB)and uses 32 KB of static RAM as a work area. There is no battery as the RAM is only used during operation and no data needs to be saved across power downs.

A Sony MPF11W-10WP 3.5″ DS/DD diskette drive was used in the DataDisk, which can now be replaced with a Gotek drive – see above. Some hardware bugs were sorted out in the DataDisk manufacturing life, some to do with MIDI timing and signal levels. Mine has a few kludges.

OS Versions The latest OS versions are 1.03 (non SQ) and 2.10 (SQ) and there are many versions below this final numbers, so its well worth getting 2.10 which cures all the known bugs. It was released in November 1991. The service manual explains the version history and bugs, the OS EPROM is available on eBay.

 

 

E-mu Systems AVI

Emu Systems AVI

Overview The Emulator I was released before the advent of MIDI in 1983. The MIDI specification was created by Sequential Circuits and Yamaha, and E-mu Systems were not able to add their influence. They were after a RS422 serial protocol – which is much faster than MIDI. This is why early Emulators and Emax’s had the RS422 serial interface – which allowed connection to Mac computers. Dave Rossum (quite rightly) thought this was a better and faster interface than MIDI. However MIDI won the day, and the faster RS422 standard never took hold.

So although the Emulator I eventually gained a JLCooper MIDI external interface, for the first few years owners were after a CV/Gate interface to enable the Emulator to be driven from other keyboards and most importantly from the new microprocessor digital sequencers – such as the Roland MC-4 and MC-8. Thus was born the Analog Voltage Interface, model number 6040.

Tomita The original Analog Voltage Interface was probably commissioned by Tomita for use in his 1981 Album of Orchestral music, with the Emulator playing Timpani from a MC-4B or MC-8. The Steve Miller Band used an E1 and this interface on their early 1980’s albums. Vince Clarke used one in 1983, probably with his famous MC-4B.

Blue Box The Analog Voltage Interface is a large metal blue box with a sloping front. There are 8 sets of CV and Gate jack inputs, located right on the front panel, one for each of the eight voice channels of the Emulator I. Below these inputs are eight toggle switches which control the mode of each channel. The three modes are:

  • Test – manually switches the channel CV into the E1
  • Internal – switches the test CV off
  • External – external gates control the E1

The Blue box links up to the Emulator I via a standard RS232 serial cable. The socket is round the back of the AVI. The voltage per octave can be trimmed via a trimmer which can be accessed through a small hole in the AVI front panel. The AVI must be used with the correct Emulator OS software, or samples can be damaged.

AVI OS Software

AVI Software The special Emulator OS version EP8SA.0308 for the AVI box has some additional functionality.

  • Mono Mode – monophonic mode on channel 1
  • Disable/Enable – turns AVI control on and off
  • Gate Test LED – GET SEQ LED shows key on/off
  • Scan Rate Control – speeds up the response time to CV’s

Technical The AVI has a Z80 micro-processor running at 5 MHz with a 2716 EPROM for the simple operating system. The control voltages are read by an ADC0809 8-bit analog to digital converter. The AVI software behaves as if it were the internal sequencer, so this functionality is disabled in the Emulator. The keyboard is still active, but its best to switch it off using the Scan Rate Control, as the response to CV/gates improves by 10 ms to 3 – 4 ms.

Success? Well this box is pretty rare, probably around 50 or so were produced from 1981 – 83. We know of only three in existence today and I owned one in 2000 along with four Emulator I’s. When I spoke with Dave Rossum in January 2001, he commented that it was one of the more unusual and less successful items that E-mu Systems made in the 1980’s. However low demand for a CV/Gate interface, is understandable, especially once MIDI took off in 1983.

Emu Systems AVI Rear

Connections The AVI is connected to the Emulator via a RS232 serial interface and cable. The Emulator acts as the DCE and has a DB25 female socket. The AVI acts as the DTE and has a male socket. The communication protocol is very basic with only TX, RX and GND signals being used by the AVI, although the Emulator has a more complete RS232 implementation. The RS232 socket is wired to the Emulator digital board via a ribbon cable, and it enters the board via a DIL header called IC41. Therefore a standard serial cable wired as follows is required. Only the lower 3 connections need to be made.

E1 DB25 Cable has Male Plug E1 IC41 pin AVI DB25 Cable has Female Socket
6 DCE Ready 7
20? DTE Ready 11
5 RTS 12
4 CTS 13
3 TX 14 RX 3
2 RX 15 TX 2
7 GND 10 GND 7

Korg Wavestation Refurb

Overview I bought my Korg Wavestation new in 1990 as a grey import with no serial number for £1200, £400 of RRP. It was a big purchase for me back then, and my first digital synthesizer, which I used for many tracks in the early 1990’s. I loved the wave table sounds and the keyboard with after touch. I added a few sound cards, Drums and Performance 3. As my studio grew the Wavestation was rather side lined and then put in the garage for storage for 20 years, where it gathered dust and scratches.

In 2020 I dug the WS1 out to refurbish and possibly sell, but once plugged in and making sounds in the new Garden Studio I decided to keep it. I do have iWavestation on an iPad but it is not quite the same as the original in sound or play-ability. It does have the advantage of displaying the waveforms.

The Refurb My Wavestation needed a new back light, new front panel buttons, keys cleaning and some scratches on the screen removed. The scratches on the panel, created during its long stay in my garage would have to stay. The component values referred to in this post are for the original Wavestation, the component numbers and values are different in the AD rack version. The disassembly of the Wavestation is a complex and lengthy process, I photographed and documented every stage. Here is a visual guide and more information on the new LED replacement process.

New White on Black Display

New LED Display The large 64 x 240 LCD is best replaced with a modern LED display which is nearly plug compatible, it lasts longer and enables the noisy inverter to be removed. I bought my white on black display from BuyDisplay with the pin connector fitted. The display is connected to a 20 pin-header on the main PCB at CH13A, I made a new 20-pin ribbon cable with sockets to connect to the new display. I reused the old 2-wire LCD EL power cable that goes to CN11A (CN4 on early models) on the PSU board, with a minor change to the board (detailed below).

Here is a list of the changes needed:

  • Pins 19, 20, 21, 22 should be removed or cut from the header on the LED display.
  • Pin 19 needs to be connected to Pin 3 (+5V) using thin wire to ensure the right font is used.
  • Add a 3K9 resistor between Pin 2 and Pin 4 to modify the contrast voltage.
  • Connect the A and K terminals on the back of the display to the old LCD back light cable.
  • Remove EL transformer (T2) from the PSU board.
  • Remove C28, C29, R17 and R18 from the PSU board as they are not needed.
  • Add a 100R resistor between +V pad of C28 to where Pin 4 of T2 was.
  • Replace R17 with 6K8 and R16 with 3K9 resistors, to get the contrast correct.
  • I replaced C30 on the PSU board with a modern MLCC 100nF capacitor, as preventative maintenance.

Once all the modifications are done and checked, the Wavestation can be reassembled, and powered on. The display works very well, although not exactly a black background it is very close, and it makes using the Wavestation a joy.

EX Upgrade The Wavestation of 1990 can be upgraded to EX capability by installing 4 additional wave ROM’s (total of 2MB) and the EX OS which is at version 3.19. The EX upgrade was more about drums and piano, but there are additional Prophet VS waves in there as well. A total of 119 waves were added and 8 more digital effects added, most of the new wave sequences are rhythmic.

OS ROM 3.19  The operating system is contained on two NEC D27C1000A-12 ROM chips (the Wavestation AD uses the -15) at IC18 and IC19, they together hold 256 Kbytes of data. They have a slightly different pin out to modern equivalents like the MBM27C1000A-15Z, which need pins 2 and 24  swapped during programming. I have used the original chip type to avoid complications. The OS binary is available from the Synth ROM Database.

Wave ROM The wave data is held in four 512 Kbyte Mask ROM’s (2 Fujitsu and 2 NEC) that have been encoded at the factor, with a total of 2MB. We need to use EPROM’s that we can burn with the wave data and I have used ST M27C4001-12F1 chips encode with the wave binaries available from the Synth ROM Database. Four 32-pin turned pin IC sockets were soldered onto the main board along with four 100nF 2.5 mm spaced ceramic capacitors. The four new ROM IC’s are located in the sockets as follows:

  • IC2 – WS4P0
  • IC3 – WS3P9
  • IC4 – WS3P8
  • IC5 – WS3P7

I bought the chips and had them programmed by buyicnow.com for under £50 including postage. This a a very easy and cheap way of getting the upgrade chips and sockets. The original Korg upgrade was £300 in 1992.

The Prophet VS Legacy The Wavestation is a major development of the Prophet VS from 1986 and most of it ROM waves were reused, the Wavestation added wave sequencing as well as many more waves than the VS. The 1990 Wavestation uses Prophet VS waves from 35 to 125, including bells, vocals and some traditional Piano and Bass waves.  The Wavestation documentation does not contain a description of these waves but with some detective work looking at the Poly Evolver waves which are also VS waves, its possible to add the wave descriptions, which are here Korg Wavestation – Prophet VS Wave Descriptions.

The Wavestation EX added in the Prophet VS waves 126 to 155, however the ROM memory in a VS stops at location 127, so these 30 waves are possibly from one of the six Prophet VS RAM cartridges which contain 32 waves. The VS126 to VS155 waves are visible in iWavestation but there are no descriptions.

Korg WSC-3S Cards

Patches The Wavestation comes with 3 banks of sounds, one in ROM and two in RAM. Korg produced quite a large library of patch cards as well as three PCM cards with new waves, and many professional patches were commercially released by companies in the 1990’s. A full list is here. I have a large library of sysex files stored on my PC and my personal favorite patches are loaded onto a MCR-03 RAM Card. I use the iWavestation to preview patches and then I load them up via sysex.

The Wavestation was commissioned into the studio on 8th April 2020 and replaces my S-50 in my active setup (as the W-30 has 240MB of S-50 sample banks on hard disk). The refurb has worked really well and the Wavestation now gets lots of use in creating new songs, the key is to try and avoid all the presets that have been overused in the 1990’s .

PPG 350 Computer Sequencer

PPG 350

Overview The PPG 350 is one of the first digital sequencers ever made and only 15-20 were made from 1977. I have tried to document all the known information about this fantastically quirky sequencer, which was used by Tangerine Dream, Klaus Schulze and other German musicians in the late 1970’s. It was more sophisticated than analog step sequencers and was sufficiently ahead of its time to be useful until the Roland MC-4 arrived with 4 note polyphony.

Back in 1976/77 I was at University of Essex working on mainframe software and I could see the emerging microprocessor revolution but had no access to the technology. Over in Germany Wolfgang Palm was seeing the same revolution but he was also able to harness it.

He bought a Motorola 6800 development system in 1977 which was the genesis for the 350 and the later Wave synthesizers. At the same time Roland launched the MC-8 digital sequencer using the same 8-bit microprocessor technology (Intel 8080) but taking a different and rather tricky approach to note entry.

I don’t own a PPG 350, so the pictures are from a VEMIA auction in 2016 where one sold for £600. If you want to sell one let me know!

6800 Exorciser

Technology  The 350 uses an early 8-bit microprocessor, the Motorola MC6802P with 128 bytes of internal RAM space, which was launched in March 1977. The software program is held in 4 x 1k byte 2708 EPROM chips. There is also a set of TTL and CMOS logic which probably provides the rate clock circuit and helps scan the keyboard and switches. There are also a battery backed up 128 byte RAM chip (unsure what this stores) and 4x AMI 22 pin chips – probably sequence memory.

There is also a DAC circuit, possibly a R2R ladder for creating the note data. Its likely the 8-bits held 6-bits of pitch CV and 2-bits of timing data (Gate, Trigger 2 and Trigger 3). There is also a SPDT reed relay on the motherboard, maybe controlling memory protection.

There are a least 3 versions of the motherboard PCB; different RAM chips, layout and PSU either fully or partially on board the PCB. We know the prototype PSU overheated. There is also a PCB for the panel controls and a set of jacks and an RS232 socket on the rear, and a daughter board for the Sync In and Out. The 350 clearly went through some changes during its short manufacturing life, including some jack sockets not being connected.

Left Panel

Front Panel The sequencer is controlled by a number of dedicated buttons with LED’s or 7 segment numeric displays, as LCD displays were not available for another 5 years. This approach conventionally splits out the various OS functions across the panel and is user friendly albeit rather digital!

The 350 uses the first 16 keys on the keyboard as a numerical key pad for entering data, and the whole keyboard with a split at Middle C to control data values up/down around Middle C. This is all labelled on the front panel and its important to understand how the keys control the sequencer.

Rear Panel Sockets There are nine 1/4″ jack sockets for the following outputs:

  • Added Trigger – trigger P3
  • Multi Trigger – trigger every step
  • P2 Trigger – additional legato trigger
  • Gate – primary gate from the sequence
  • Selected Trigger
  • Pitch CV – sequence pitch CV
  • Sync Out – High frequency clock out
  • Sync In – High frequency clock in
  • Ext TR Input – 5V trigger pulse to clock the sequencer (Stop button LED lit)

There are also trimmers for the offset and scale of the CV signal and a RS232 socket for GATE-OUT.

Right Panel

Sequence Number The sequence number (1-16) is displayed in a 2-digit 7-segment LED display and is incremented by the Sequence Number key. In Record mode holding the sequence number button stores the sequence, in Playback modes holding the button recalls a sequence 1-16 into memory. Total sequence memory is a maximum of 256 notes and the System Overload LED is lit when this is exceeded and no further notes can be stored.

There is a memory protection ON/OFF switch on the rear of the casing. If unquantized timing data is recorded then the number of notes that can be recorded drops to 128, as storage is needed for the note interval data.

Operation Mode There are 10 keyboard modes, which are selected by pressing and holding the MODE button and using the keyboard to select the mode number (0-9). The modes range from the basic record and playback to arpeggios and sequence chaining.

Mode 0 – One Note Keyboard In this mode the 350 works like a normal monophonic synthesizer keyboard, but with 3 different triggers (gate signals) available, and the last played note is stored digitally (for long stable notes). The musician can play up to 3 connected synthesizer directly from the sequencer and does not need to switch from one keyboard to another, because of the 3 gate/trigger signals. The pitch CV has no be shared, so the 350 is not polyphonic.

Mode 1 – Playback This mode is for playing back a previously recorded sequence. A root note is played on the keyboard and then the computer plays back a sequence or a chain of sequences using the Start button. The sequences can be with “timing” (different note intervals) or without “timing” (quantized), and this is selected by the Timing ON/OFF button prior to the sequence being recorded. The sequence can be transposed up or down by playing different root notes on the keyboard before or after the sequence is started, allowing real time transposition. A root note of middle C plays the sequence as recorded.

Mode 2 and 3 – Immediate Playback  These modes are useful for live playing. Once a phrase has been played on the keyboard it is immediately played back once the end of the phrase has been reached.  The timing of the notes is the same during playback and corresponds to the average of the first two notes played. The difference between Mode 2 and 3 is unknown.

Mode 4 – Arpeggio 1 This mode is a traditional chord arpeggio, which plays the keys held down in sequence and continuously.

Mode 5 – Arpeggio 2 This mode is a chord arpeggio, not sure how it differs from mode 1.

Mode 6 – Cascade Assume this plays the notes held down as a single arpeggio, rather than repeating

Mode 7 – Record The 350 can store a maximum of 256 notes in persistent battery backed up RAM. Sequences can be deleted and re-recorded at any time, and the sequences are stored during power off. The 256 notes can be 16 sequences with 16 notes each or a single sequence with 256 notes, or a sequence with “timing” data and 128 notes of any combination. The sequence is played with the keyboard and then saved using the procedure explained above, with a sequence number (1-16).

After recording it is important to stop the sequencer immediately and IN TIME by using the Stop/Run button to stop the recording. All note intervals have been recorded, and the interval you recorded after the last note is released and pressing stop will also be recorded.

Mode 8 – String Programming  This mode enables a string (or chain) of sequences to be recorded, by recalling and saving a set of existing sequences into a new sequence number. The number of the sequence, the basic pitch, and the number of runs are stored in a chain for each partial sequence. To chain sequence 1 and 2 and store it on 3, select Mode 8 and Sequence Number 3, play the root note the number of times you want it played and then the sequence number that you want (1), then repeat for sequence 2. Choosing a different root note will transpose the sequence.

Mode 9 – Event Correction This mode enables sequences to be corrected or changed. Each parameter of a note can be selected individually (pitch, time, trigger, added trigger) and then changed.  The type of sequence data that is being changed is selected by the Parameter Timing ON/OFF button and displayed in the 7 segment display to its left. Parameter values are:

  • P0 = control voltage
  • P1 = timing (note interval)
  • P2 = trigger P2 (legato)
  • P3 = trigger P3 (additional trigger)

To change the pitch (CV) select P0 and use the Step button to locate the note you wish to change, now press the correct note on the keyboard. To change the note interval  select P1  and use the keyboard to change the note interval. Middle C leaves it unchanged, keys above Middle C will increase the pause and keys below mid. C will shorten the pause. Hit the key twice to de/increase the note interval, related to the the distance to middle C key.

Rear Panel

Trigger Mode (Outputs) In 1977 the synthesizer world was analog with basic monophonic Pitch CV and Gate external controls, and with larger analog modular synthesizers providing additional CV or gate inputs to control extra VCO’s or ADSR’s. The control of polyphonic synthesizers would have to wait a few years until the arrival of DCB and then MIDI. The target customer for the 350 were the German based synthesizer musicians such as Tangerine Dream and Klaus Schulze who owned large analog modular setups at the time.

Therefore the 350 was designed to be used with analog modular synthesizers, it was monophonic and had different trigger modes so additional trigger signals could be used for controlling more ADSR’s and creating more complex sounds. On the right hand side of the panel is a 4-way rotary switch for selecting the output trigger modes. These are:

  • Gate
  • P2 Trigger
  • Multi Trigger
  • Added P3 Trigger

I think these modes are incremental rather than being independent.

Single Loop This button controls whether the sequence is played once or continuously looped, with LED on/off indication.

Immediate/Delayed This button controls whether a transposition is immediate or after the current sequence has been played to the end, with LED on/off indication.

Up Down Arrows  These buttons have various functions in Play, Arpeggio and Cascade modes and they have LED indicators. Three modes are assumed:

  • UP ON – sequence or arpeggio plays forward (default at power on)
  • DOWN ON – sequence or arpeggio plays backwards
  • Both ON – Alternating sequence or arpeggio, forwards then backwards, repeated

The LED indicators in the buttons are lit according to the three modes.

Run/Stop – This button starts and stops the clock and sequence with LED showing Run/Stop status.

Step Button This button steps the sequence incrementally forward one note at a time

Reset This button resets the sequence back to  the start.

Clock Rate This knob controls the clock rate of the sequence and there is a LED indicator of the rate.

Parameter / Timing ON/OFF This button has two functions; controlling the parameter number and how timing data is recorded. With the LED OFF the sequencer records with changing note interval lengths, playing legato or staccato can change the trigger P2 parameter. With the LED ON the timing is quantized to the clock rate with each note interval the same, this reduces the data stored so 256 notes can be retained.

A Modern Replica A modern version of the PPG 350 could be easily created using a powerful micro controller (PIC or STFM) and with a lot more note memory and accurate DAC’s. The control surface could remain the same maybe in a 70 HP Euro Rack panel, with a MIDI IN being used to enable keyboard programming. However such a clone seems unlikely as modern sequencers are far more powerful, however the analog modular renaissance might just have space for this!

 

 

A&H Spectrum Mixer Refurb 2

Overview The A&H Spectrum finally arrived on 20th January 2020, very well packed and at 59 Kg! After some serious unpacking the refurb can now begin, with the PSU being the first to be looked at, so that I can power on the Master/Group section initially then add the Channel sections.

PSU Refurb The power supply is an Allen & Heath RPS3 from 1991 (serial number 7) and is a 3A linear power supply based on tried and trusted LM723 chips. Whilst the metal chassis has some rust patches rusty and the PCB is old, it looks in ok shape, although the 48V rail power cap is either bulging or has a dome! After carefully checking the power supply components I switched it on; +16.3V, -0.8V and +48V. So looks like we need to replace a component!

The original reservoir capacitors are 10,000 uF 35V with 85 degree temperature rating. I want to fit large capacitor values at 105 degree rating, but I am limited to a 30mm diameter as that is the size of the mounting. I located 15,000 uF 35V 105 degree capacitors made by EPCOS and fitted them. This will reduce the ripple voltage into the regulators down to 100 mV.

The LM723 chips have date codes from 1988, so these were replaced and I added IC sockets, then all the smaller power capacitors and the original MJ3001 power transistors and bridge rectifiers were replaced. One of the bridge rectifiers had failed, hence no -15V rail. Remarkably the 723 has become obsolete, so it is was a good time to buy some before they get expensive.

RPS3B and Heat The power supply has been upgraded to the B version, which outputs 4A rather than 3A, but no change was made to the thin 4A 16/0.2 wiring, and as a result all the wiring to the rectifiers has been heat damaged and become brittle and broken, which explains the -15V rail failure. I replaced all the wires into the regulator PCB with thick 32/0.2 which is rated at 10A, this provides a healthy safety margin. I also checked the current limiting resistors and they are not damaged. The refurbished power supply powered on successfully and the voltages were trimmed to 16.00 volts.

The original transformer is a traditional open frame model at 225VA. It provides two secondary circuits at 21.5V for the 16V rails and one at 50V for the 48V phantom power. I am keen to switch in a toridial transformer for the main rails and it has to be 225/250VA which means a diameter over 100 mm. I will have to mount this on the inside of the front panel, as that is the only space big enough. Alternatively I could just buy a cheap secondhand RPS11 which has 5A rails and a toridial transformer – lets see what eBay offers!

Fader Cleaning The high quality Alps K-series 100 mm faders are in generally good condition but they needed a deep clean as the action was not smooth. I started with the Group and Master section and took them apart, cleaned them with IPA, then Dexoit Fader cleaner, and finally put some fader lube on the lower brass rail. Each slider was cleaned so that it would slide from one end to the other on gravity alone, once apart. Sometimes steel wool was needed to remove corrosion on the brass rail.

I may buy two new Alps faders for the Master section but lets see how well the cleaning has worked. At £15-20 each I don’t want to replace all 26. I will clean the Channel faders as part of the Channel refurb once I see what issues there are in each of the channel cards.

Fader Knobs The black slider caps are nice and chunky but well worn with the white line disappearing, however I do have all 26 in place! I will have to keep them as modern caps are too short and stand proud of the panel or it means dropping the fader down by 4mm which is really not possible as there is no room in the chassis.

Panel & Knob Cleaning Whilst I waited for parts to arrive to get the RPS3 working, I cleaned the front panels with surface cleaner and deep cleaned every knob and switch cap (after removing them). This was a very long, but worthwhile task. A small number of knobs were broken or missing, as were some caps. I ordered 8 new knobs which are slightly taller and not faded! I put them in the AUX sends section, thereby releasing some original knobs and minimizing the colour change from new to old.

The brown caps for PAN are not available, so I ordered 30 light green caps and a couple of red and blue caps were also needed but I am hoping these colours match the originals. The caps are slightly smaller and need a little glue to remain in place.

Power On and Testing Once the PSU was working I plugged it into the console and powered up – all ok, no smoke! Testing uncovered a number of issues:

  • Right Master Out no signal (solved)
  • LED bar graph display 1 – 8 non functional
  • Group 2 and 8 input from bus failed
  • Channel 5 intermittent

The rest of the circuits seem to work ok, the switches are noisy but this reduces with use. The noise floor is good but some channels seem to distort easily and there are different levels in the Groups.

Group Channel Refurb The eight Group PCB’s are in good condition but not all working at the same volume. The plan is to upgrade all the electrolytic capacitors and make further changes depending on the outcome of the Channel 1 upgrade. Care is needed with these 30 year old PCB’s, and I use a vacuum desoldering gun to minimize the risk of tracks lifting.

Master Section The master section has a right channel failure, and there are no schematics available for this section, so I am using the Sabre master channel which is not quite the same design. The right channel failure seems to be a simple plug connection that righted itself on re-cabling. The main upgrade in the master section will be to replace the balanced output drivers (NE5532 with trimmers) which live on a separate PCB attached into the Master PCB, with THAT 1646’s on a new PCB.

Input Channel Recap

Input Channel Refurb Channel 1 had a broken shaft on the PAN pot, so I had to pull out the PCB to swap this with a new one, which was easy. At the same time I replaced the electrolytics with high quality Panasonic capacitors (Audio and Power versions), and removed the signal path TL072’s (IC 3-6). I soldered in IC sockets and initially tried a set of TLE2072 Op Amps from a AMEK Rembrandt channel, as these are fast low offset but with only a 14% increase in power current consumption.

I added 100nF decoupling capacitors to every Op Amp, underneath the PCB, as there is only one 15nF for the whole board!

This is an experiment to see if upgrading actually provides any benefits, as the cost per channel is around £15-30 depending on which Op Amp I use to upgrade. The change to the TLE2072 provided a clearer sound and the EQ was improved. The standard EQ uses Mylar capacitors, whilst high end consoles used better capacitor types. The PCB space is tight, so polypropylene capacitors are too large, so I am trying a set of PPS capacitors.

Input PCB

Input Conn There is a small PCB for each input channel that holds the jack sockets and XLR, it has a dual TL072 Op Amp to enable the -10dB and +4dB gain switching on the Tape Input. I have upgraded the Op Amp to a TLE2072. There is also space on the PCB for a SSM2142 Balanced Output chip, and its clearly marked on the silk screen.

This addition provides a balanced output for the Channel Output, which can be switched from Bus Out to Direct Channel Out from the front panel. I soldered in an IC socket and added a SSM2142 for the first 8 channels, as these are used as recording inputs to the Focusrite Octopre. The two 22R resistors need to be removed to ensure the Channel output signal goes into the SSM chip rather than straight to the jack socket.

Tracking Setup The Spectrum is used for tracking up to 32 synths/samplers into Cubase using eight Groups. Cubase is used as a 16 track analog style recorder with analog tape plugin available on every track. A key principle is to be constrained to 16 tracks and not to add more. The channel EQ and the two main FX processors can be used on tracking. I have constrained my use of Cubase plugins to just a TC2290 delay and the Softube Tape, no other EQ or effects are used.

16 synths come in via the Channel line inputs and another 16 via the Group line inputs. The first 8 channel outputs go into Cubase via a Focusrite Octopre which has compression available. I can switch these from Group to Direct Out, if I want to record the first 8 synths directly into Cubase, and the Spectrum outputs are balanced,

Mix Down Setup The Spectrum is also used for the final mix of a song, with 16 outputs from Cubase going into the unbalanced Tape inputs on each channel or they can be brought into the Groups. By leaving them on the channels I can record 16 synths at mix down from the Group line inputs. The stereo master of the desk can be recorded onto DAT and/or into Cubase. All four hardware FX processors can be used in mix down.

 

 

A&H Spectrum Mixer Refurb 1

A&H Spectrum

Overview In December 2019 I acquired a 16:8:16 Allen & Heath Spectrum Mixer as the center piece of my studio. Why would anyone use an analog console dating back to 1991! Well it enables me to use a hybrid recording setup, with my Cubase DAW acting as a digital multi track recorder and the analog desk is used for tracking and mixing out of the box. I gain a hands on workflow with outboard hardware but at the cost of some signal noise.

The Plan I had been looking out for a medium sized 8-bus analog mixer that could be upgraded and therefore used THD components. An Amek would have been fantastic but too big, and outside my price range. The Spectrum (sometimes called Sabre 8) is a well built desk that is smaller than a full sized Sabre with 24 or 32 channels and has only a 3 band EQ, but it has all the important routing I need and the addition of MIDI mute automation. Most of the schematics are available (200 Series) and show basic TL072’s in the channels and buses, with the NE5532 in the pre amp and bus master.

Connections The Spectrum is connected to Cubase Pro (Windows 10 PC) by a Focusrite 18i20 and OctoPre Dynamic, with 8 inputs from the mixers 8 group outs, 2 from the Main Mix and 16 outputs back to the tape inputs, all on balanced cables. There are six AUX busses with five hardware effects connected (PCM70, PCM80, REV7, Alesis Midiverb 4 and SDE2500) and AUX 1 used as a input to my Roland S-50 Sampler. My synths and samplers are connected to the 16 channel line inputs and the 16 Mic XLR inputs that have been converted to line inputs, I can switch between the two line input groups on each channel.

Tape Machines A Tascam DA30 DAT is the main tape machine connected to the Control Room analog outs, and replays into the Tape 1 input and the Focusrite SPDIF digital input. A Yamaha MT4X 4-track cassette tape machine records from the duplicated Bus Outs 1-4 and plays back stereo into the Tape 2 input.

Refurb Plan The Spectrum needs some minor repairs, a clean and refurbishment, although it powers on and works. There is one broken GAIN pot and four broken or missing control knobs. The power supply is rather beaten up and needs a service and clean. I suspect some of the MIDI muting thats uses JFET’s maybe dead. The plan is to strip the mixer and refurb the Master section first, followed by one input channel and one monitor channel, to see if the Op Amp upgrades and recap produces a better sound and noise floor.

The project objectives are:

  • Recap and restore the power supply
  • Change the Tape Inputs to balanced
  • Change the Group Outputs to balanced
  • Upgrade the existing balanced outs (EPOS modules)
  • Possibly upgrade the Op Amps in the signal path

Op Amps I have to be careful not to spend too much on the Op Amp upgrades as there are over 130 of them! I can afford to use a high quality bi-polar SOIC Op Amps with adapters to replace the NE5534, but with over 100 TL072’s in the mixer, I need to keep to a THD Op Amp for these. Options include; OPA1642, LME49720, LT1358 and OPA2134. With the use of low offset Op Amps it may be possible to remove some of the 14 electrolytic caps in the signal flow to open up the sound or at least fit bypass caps. The EQ capacitors could be replaced with high quality Wima 2.5% polypropylene, and the TL072’s in the metering circuits will be left alone.

Battered PSU

PSU The power supply is the stock Allen & Heath RPS3 which was also used in the larger Sabre consoles and is rated at +/-16V at 3A. I will replace all the capacitors, IC’s, power transistors and upgrade to toridial transformers. I aim to use larger reservoir capacitors as in later power supplies, to reduce ripple. A new PCB may be needed. I also need to bend the front panel back into shape and clean it. I decided not to replace the PSU with a Blue Dog version as it would give little or no benefit in audio performance, but a cheap RSP11 would be useful.

I will post progress updates as I work my way through this project and share the challenges and how it sounds when completed!

 

Roland W-30 Refurb

Roland W-30 As Bought

Overview I bought a used Roland W-30 in September 2019 with a faded LCD and broken encoder/missing knob for a low price of £100, and it came with 40 DS/DD diskettes with various sample banks and the original manual. The W-30 was exactly 30 years old, made in September 1989, by which time Roland had already sold 2000.

It is a typical example of a well loved and highly used W-30 in the UK. The exterior and electronics are in good condition but its shows signs of lots of usage! The work needed is relatively easy and cheap and will bring the W-30 back to original condition along with some nice upgrades.

The W-30 was introduced in early 1989 at £1599 in the UK and is the 12-bit S-330 reworked as a keyboard with a full MC-500 style sequencer and SCSI as an option, the TVF and TVA from the S-550 were included but sadly no effects section. The DAC is 16-bit is not Burr Brown but the same chip used in the S-50 from 1986.

Broken Encoders

The W-30 work station sold very well for the next 3 years with 10,000 units manufactured. A large 240 x 64 LCD replaces the video monitor, so programming is bit tight on screen space but the OS is familiar and easy to use.

I plan to use the W-30 for ambient music and sampled dialogue, a S-50 with resonant filters and SCSI, rather than as a Techno Prodigy creator. The use of 10 or more short samples is the typical home for the W-30, creating a sample workstation.

New Encoders

Initial Power On Before any repair work started I switched the sampler on, and it booted the OS and sample disks fine, but was hard to use in its current state! The front panel switches were very worn out and didn’t make contact, and I could hardly see the LED’s. All the keys worked fine which is unusual for a 30 year Roland key bed, so key contact replacement is one job that is not needed.

New Encoders I replaced both encoders with new ALPS versions and black metal encoder knobs. The knobs are a bit higher than the originals, but I mounted them as far down as possible. The limitation is the need to tighten the knobs onto the encoder with a hex key. They work well and look the part.

Some care is needed to get the new encoders exactly in the middle of the old holes as the shaft diameter is smaller. The wiring changes are explained on a installation guide that comes with the encoders and only the output board needs removing to do this job.

Inside

Full Tear Down The next set of upgrades and repairs needs the whole casing and all the PCB’s unscrewing, as we need to get to the front panel PCB, which is a complex job. So I did this as one exercise; new LED back light, new switches & SCSI upgrade.

New Display The contrast pot did its job but the EL back light was completely gone and worse still the inverter was whining loudly. There are two options; Replace the back light EL strip and the inverter or fit a new LED display that is a pain to fit but provides a nicer display and provides a long term solution. The LED display I used is not thicker than the original, which means the display bezel is flush to the panel.

I went with a new ERM24064DNS-1 (240 x 64) LED display with white lettering on black background from BuyDisplay here. This is pin compatible but needs some minor modifications to work correctly (detailed documentation is here). There are two cables to the display; CN12 which is a 20-way ribbon cable with a Hirose connector at one end and CN10 which is a 3-way cable for powering the EL backlight or LED. I patched the original LCD cable into a 20 pin DIL cable that attaches to the LED display, as making 18 new Hirose connections is very tricky.

  • Patch a new 20-way IDC cable into the original, retaining the Hirose connector, red stripe is Pin 1.
  • I used an ISC plu and socket to connection the two cables.
  • Connect Pin 1 of the LED to frame ground using the black cable that is wired to the old LCD
  • Remove Pins 21 and 22 on the LED header so its clear where the 20 pin connector goes.
  • It is very difficult to remove the inverter transformer at T1, so leave it in.
  • Remove C26, C27, C28 and Q1 from the main PCB.
  • Connect a 100R resistor between +5V on the C26 + terminal and T1 pin 4.
  • Reuse the CN10 cable and connect +5V to A and GND to K on the back of the LED.
  • The original contrast adjustment onto Pin 4 remains the same.

The 100R resistor limits the current to the LED, as the correct brightness is at 120 – 160 mA.

Bezel Removal The LCD is glued with double side tape to the display bezel and its hard to remove and must be done carefully. I removed the old LCD from the metal frame by straightening the tags and letting the LCD come away from the frame. The next stage is to carefully heat up the glue with a hot air gun or hair dryer, then using a plastic prise tool separate the bezel and panel. DO NOT use any metal instruments as this will scratch the bezel. The bezel should be attached to the new LED display with double side tape once the diaply is in the W-30 to ensure the correct alignment, its the last job to be done but it takes ages to get all the glue removed,

Switches & LED’s All 29 tactile switches were replaced, and I checked the double sided tape that holds the plastic buttons in place, as some buttons were sagging below the front panel surface. It looks like the plastic hinge in the button has weakened with age. I decided not to replace the LED’s even though they are a bit dim.

SCSI2SD Drive

SCSI Connection The W-30 has all the connections for external SCSI and just needs a MB89532A 40-pin chip and OS 1.07. Roland sold the W-30 without SCSI (except in Japan where there was a W-30SC) and charged a fortune for the chip to be fitted. You can buy these together as a kit on eBay but I ordered my chip from UTSource for £2.50 as part of my regular orders. The chip was carefully inserted once I had the W-30 apart, and OS 1.07 was downloaded and a boot diskette created. The upgrade worked first time and SCSI drives could be formatted.

Initially I was planning on replacing the floppy drive with a Gotek version to provide easy access to sample banks, but with SCSI working I have gone with a SCSI2SD drive. The W-30 has to have a floppy drive connected or it wont boot, even though it will then go onto boot from a SCSI device. There is not much additional space inside the W-30, so I have fitted an external SCSI2SD 5.5 drive directly into the SCSI connector, no cable needed! There is no power to the W-30 SCSI connector on pin 25, so the drive is powered from USB and shares a dedicated USB power supply along with my Boutiques.

The SCSI2SD has been portioned into 4x 80 MB drives (the maximum possible) with SCSI ID 1-3 used for the factory libraries which can be found here, abs SCSI ID 0 being my favourite samples. I converted the hard disks to W format (takes ages) but found SCSI ID 1 would go unformatted every so often. So I will try a different SD card. I also copied the system disk to the hard drives so the W-30 will boot from the SCSI, which is much faster than floppy.

Sample Disks My W-30 came with around 40 sample disks in good condition, some of them from the Roland factory but others are from MusicMark in the USA (details here) and a company called Streetwise. There are 10 bright green Music Mark disks, all of synthesizers available around 1992, from Juno 106 to Korg M1. One or two nice samples but not very well looped and 8+ banks so each sample is usually less than 2 seconds. The 12 Streetwise disks were similar in quality, samples of synthesizers both analog and digital from the early 1990’s. There was also a CD with further sample disks from unknown sources. I have copied these onto my hard drive ID 0.

The Roland W-30 was commissioned into the studio on 10th April 2020.

 

Roland S-750 Refurb

Overview I bought a used S-750 in May 2018 for £85, which is a bargain, especially as it has an expanded 18 MB of sample memory, and was from Air Studios. It was manufactured in February 1993 and is a fairly late model although it does have wire kludges to the main PCB. Whilst it is rather large and heavy I plan to upgrade the sampler and use it with 7 Roland sample CDROM’s permanently attached on a SD card in the casing.

New LCD

New LCD The back light of the blue and original LCD had faded. Rather than just replace the back light EL I decided to replace the complete LCD with a new grey and white one which I bought off eBay to ensure it worked.

It does work and look great, but its a few millimeter higher than the original so the perspex screen has to be fitted back in 2mm proud rather than smooth to the front panel. It is a very nice LED screen. It is not easy to remove the perspex bezel from the old LCD as the double sided tape had hardened over the years.

SCSI Drive I wanted to fit a SCSI2SD V6 drive inside the case rather than having it taking up space outside. The S-750 main board has the connection for the external SCSI 25-pin connector and an unused 50-pin connector. In fact its just the bare PCB holes with no socket. On investigation this proved not to be a 50 pin SCSI connector or even the 40 pin socket on the S-770 which is used to connect a hard drive internally. It is a IDC 2mm pitch 50 pin connector wired as follows:

50 pin SCSI

Pin Function
16 Data 0
18 Data 1
20 Data 2
22 Data 3
24 Data 4
26 Data 5
28 Data 6
30 Data 7
32 PARITY
35 ATN
36 BSY
38 ACK
39 RST
40 MSG
42 SEL
43 I/O
44 C/D
46 REQ

Its a completely non-standard proprietary Roland pin out, but it does have the SCSI bus on it with power. My plan is to put a 50 pin socket onto the Main PCB and cable it to a new PCB that maps this to the correct 50 pin SCSI pin out and attaches to a SCSI2SD drive with a 50 pin socket. This will provide 7 SCSI drives which I will load with sample CDROM’s. The only down side is that I cant swap SD cards without opening the case and getting the sampler out the rack., but that doesn’t worry me given I will have 7 drives to play with.

This new PCB has two 50 pin sockets and space for the SCSI2SD drive to be mounted to the PCB. The S-750 has a convenient set of 4 hols in the chassis to mount the 90 x 100 mm PCB.

Copyright AMSynths 2019