PPG 314 Sequencer

PPG 313 & 314

Introduction The PPG 314 analog sequencer dates back to 1976 and the beginnings of PPG when they were a modular synthesizer company. The first PPG sequencer in the 100 series was a straight copy of the Moog 960, but the 300 series sequencer was a more advanced design. It was still only 8 steps and 3 CV’s but it had dedicated controls for step timing and for moving around the sequence itself. Accurate switched step timing was also used in the Roland 717 and the Synthanorma around the same time.

In 1976 I was about to go to the University of Essex and study electronic engineering, whilst I had heard analog sequencers on records by Klaus Schulze and Tangerine Dream, I had never seen or owned one. I just had my trusty PE Minisonic synth! The PPG 314 which sold for £2,000 was way out of my reach, it was a years salary!

How Does it Work The arrival of CMOS logic chips in the 1970’s really opened up sequencer circuit design, thanks to its low power consumption compared with TTL (ARP 1050). The PPG 314 uses a decade counter at its core (4017) producing 8 steps, to drive 3 sets of CV’s that are summed using 741 Op Amps.  The value of each of the 3 CV’s is set by a potentiometer for each of the 8 steps.

The single sided Controller PCB is hard wired into the Main PCB and contains the 4017 counter chip and five 4011 NAND logic gate chips that buffer the 8 step positions into the CV’s and provide the logic control. There are also individual gate output for each step, which goes directly to the jack sockets.

The Main PCB is doubled sided (with no silk screen) and it holds all the potentiometers, LED’s and rotary switches, with the 6.35 mm jack sockets mounted directly to the panel.

Voltage Controlled Clock This circuit lives on the main PCB and is based on another 4011 configured as a VCO with variable pulse width. Whilst Emu Systems and Roland were using analog VCO’s in their sequencers, PPG opted for a simple CMOS version. There are Rate and Pulse Width (0 -100%) potentiometers and a LO/HI Range switch, as well a switch to turn the external control of sequencer rate OFF or ON. A green LED shows clock rate, and there are START and STOP push buttons which are mirrored as trigger input jack sockets. This enables remote control of the 314.

Step Timing The timing control for each step is preset via a 6-way rotary switch, with these timing divisions; 1, 1/2, 1/4, 1/8, 1/16 and 1/32. This is a great feature for setting up accurate rhythmical sequences, as the Moog 960 uses a potentiometer which makes timing accuracy difficult. With separate timing control the 314 retains three rows of CV control, without scarifying one row for timing. The timing is controlled via a precision voltage patched by the switches into the clock.

Programming The lowest row of 6-way switches are for programming how each step works, and provides another level of real time control. The six positions are;

  • LAST – previous step values are used for this step
  • GO NEXT – skips the step
  • GOTO 1 – moves to step 1, and starts again
  • STOP – stops at this step, and repeats
  • SEL TRIG – sends a trigger to the SEL TRIGGER output
  • NORMAL – sequences step by step

On the front panel the lettering is a bit cryptic with a solid circle as STOP and an arrow as SKIP. The GOTO 1 is not marked as available on Step 1 and 2 for obvious reasons, but its still wired up but it means you never move off Step 1.

AM314 Panel Mockup

AMSynths 314 As part of my “Big Moog” project I wanted to replicate the PPG modules that Klaus added around 1976/77 to his Moog IIIP. These consisted of a set of analog voice modules (VCO, VCF, VCA, etc.) and a pair of 314 and 313’s. I was lucky enough to have been given some photos of the inside of some of these modules including the 314, which meant I could reverse engineer most of the circuits.

The 314 clock is based on a CMOS chip but I have upgraded the design to use an analog VCO from the Roland 104 sequencer. I could not accurately trace the CMOS circuit (which is very basic) and an analog VCO is going to be temperature stable. The rest of the circuits are the same as the original . The Timing switches use precision resistors and feed a voltage back into the Clock VCO, just as in the Roland 717. I have recreated all of the six function modes including LAST, SKIP and GOTO1.

The Euro Rack AM314 consists of 5 PCB’s rather than the original 2, as it makes prototyping easier – as well as the final build. There are three Panel PCB’s (Clock, Sequencer and Output) and two Main PCB’s (Clock and Sequencer Controller). The prototype PCB’s were laid out in Spring 2021 and ordered in March. A panel was also mocked up to ensure all the switches and pots would fit and the lettering was in the right place.

 

 

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-AB5, 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 transformer 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 electrolytic 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 performs 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 comparisons 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.

2021 Postscript It turns out the Newhaven OLED has a minor problem working with the MC500 Boot ROM. When no diskette is in the drive the Boot ROM should display an Insert Diskette message but the screen goes blank and only after pressing a number of keys does a partial message get to the OLED. It looks like the Boot ROM is failing to handshake with the OLED possibly due to timing problems, whilst the main software works fine.

This probably comes down to the speed of the OLED processor and there is not much that can be done, even swapping out to a different OLED may result in the same failure. The work around is easy – just leave a diskette in the drive.

To show Available Memory on the MC500 with OLED fitted just press SHIFT and AVAIL MEM buttons together.

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 provides the clock circuit (4011), address decoding 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, 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  PPG 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!

 

 

Roland CSQ-100 Refurb

My CSQ-100

Overview In November 2017 I bought a little Roland CSQ-100 in good working condition for a £150, with a plan to swap out the 2114 RAM memory and upgrade with more memory and the ability to store the sequence when powered off.

My CSQ-100 has a serial number of 183628, which dates it to May 1982 and probably one of the last made, as by the end of 1982 you could buy a Roland SH-101 with a sequencer built in. Then in 1983 with the arrival of MIDI Roland moved onto MIDI sequencers such as the MSQ-100. With over 3500 sold this little sequencer was a big hit for Roland at the time.

CSQ-100 History  Roland released the basic single track CSQ-100 Digital Sequencer with CV and Gate inputs and outputs in May 1979 and made over 3500 before introducing the more power 4 track memory CSQ600 a year later.

The CSQ-100 is micro processor based, using an 8-bit Intel 8048 with a tiny 2k byte operating system, which went through 2 revisions. It was usually paired with Roland’s new mono synths of the time such as the SH-09, SH-1 and SH-2.

The CSQ-100 has no lithium or nicad battery, as there is no memory retention for the single 2114 RAM chip, so your sequences are lost at power off. However with no battery to leak, many have survived in good condition, unlike the CSQ-600 which is a train wreck.

The CSQ-100 has two memory channels of up to 84 notes which can be played separately or in sequence. one after the other.   There are start and step pulse inputs but no DIN SYNC or wider interfacing capability. MIDI happened four years after the CSQ-100 was launched, but DIN SYNC was a standard in the early 1980’s.

Recap Whilst in physically good condition the PSU board needed a recap after 37 years. All the electrolytic and 100nF bypass capacitors were replaced with high quality modern replacements. Testing the power rails revealed the +15V was ok but the +5V had dropped down to +4.85V. So the 7805 regulator chip was replaced and the rail went back up to +5.00V. The electrolytics on the main board were also replaced. I use Panasonic and Nichicon capacitors.

Slider Dust Covers These had perished over the years and a new set were cut from 1mm black EVA sheet. It is important to do this as the old covers break into little pieces that drop into the switches and sliders. Using black EVA rather than a grey means that the hole around the slider or switch blends into the background of the panel cover. I also replaced the front panel screws with either new Philips head M3 at 6 and 8mm or hex cap M3 at 6mm to improve the look of the sequencer. A lot of the old screw heads had been damaged or were rusty.

RAM Adapter PCB

Non Volatile RAM It is rather annoying to loose the sequences you have carefully recorded after power off. I have designed an adapter PCB that replaces the 2114 RAM chip with a new non-volatile FRAM chip. No batteries are needed and sequence storage is 150 years. The 2114 chip is desoldered and replaced with a DIL socket, and the AMSynths adapter PCB with FRAM chip simply plugs in, you can order the PCB from OSH Park here. The SMD FRAM chip is a FM16W08.

Outcomes With the sequencer refurbished it was time to turn in on and check everything worked ok -it was!

 

 

Roland CSQ-600 Repair

CSQ-600

Overview In July 2019 I bought a Roland CSQ-600 Digital Sequencer in good external condition but not working 100%, and with the dreaded battery corrosion on the main PCB caused by the Roland Ni-Cad battery leaking. Whilst the previous owner had swapped a new battery in and kludged in 2 new wires for the failed traces, it was sold as needing repair, with possible RAM chip issues.

I bought my first secondhand CSQ-600 way back in the 1990’s and it also had PCB corrosion caused by a leaking battery. The PCB was so badly damaged that it was scrapped, as repairing was beyond my skills at the time. Fast forward 20 years and this second CSQ600 is going to be repaired to full functioning condition!

PCB Before Recap

CSQ600 History  Roland released the basic single track CSQ-100 Digital Sequencer in May 1979 and made over 2500 before introducing the more power 4 track memory CSQ600 a year later, which went onto sell over 2500 units into 1983 and the birth of MIDI. The CSQ-100 and 600 are micro processor based using an 8-bit Intel 8048 with a tiny 2k byte operating system, which went through 2 revisions.

The CSQ-100 has no battery, as there is no memory retention for the single 2114 RAM chip , so more of them have survived the decades. The leaking battery of the CSQ-600 has led to many being thrown away (such like my first one!), so they are harder to find.

In 1980 the CSQ-600 was for a brief year a powerful 600 note (analog CV) sequencer that was typically used with Roland’s CV and gate equipped mono synths of 1980 (SH-09, SH-1, SH-2 and 100M). In 1981 the mighty MC-4 arrived and was capable of 4 note polyphonic sequencing of the Jupiter 8 and Juno 60. In 1983 MIDI arrived and by then old fashioned CV/gate CSQ range was discontinued, with the basic sequencer features added into the mono synth (SH-101).

The CSQ’s languished in the unwanted category for many decades until the resurgence of analog synths and Euro Rack in 2005 onward. These basic sequencers regained some value and use, and a number of CSQ-600’s have been repaired from battery damage rather than being crushed. In 2019 their value had reached £150 – £400 in good condition.

PCB with Baking Soda

Repair Time The first stage was to open up the CSQ-600 and review the amount of battery damage. Fortunately the amount of PCB damage is relatively limited but the corrosion does not look to have been neutralised and the trace damage has not been attended to, just wires kludged in.

The PCB was removed and baking soda in a thick paste used to neutralise the battery acid, I left the paste on for 20 minutes and scrubbed the PCB with a toothbrush. In the end I did the whole main PCB.

The PCB’s in these sequencers always have excessive flux over the trace side of the PCB (see photo), which I also neutralised and removed with PCB cleaner, and then the whole PCB front and back cleaned in isopropyl alcohol.

With the PCB clean and dry I used a fibre glass pencil to remove the silk screen and corrosion on any affected traces, which included the damage near the battery but also further across the PCB. The bare traces were protected with water soluable solder and I used a flux pen to help things along. The two broken traces were carefully repaired with thin resistor wire, bent to shape and soldered onto both ends of the affected traces. The PCB was then cleaned again and dried for a few hours, before being put back in the case for an initial power up test.

PSU Old Caps

Recapping The power supply was re-capped, and the blue 40 year old electrolytic capacitors on both the power PCB and the main PCB replaced, along with any ceramic bypass capacitors. The replacement power supply capacitors are Panasonic:

  • One 1000uF 16V EEU-FC1C102S
  • Two 470uF 35V EEU-FC1V471
  • Four 10uF 25V EEA-FC1E100H

I also replaced the 470nF and 1uF electrolytics using Nichicon UFW audio grade capacitors on the main board, as I had these in stock.

Initial Test TO BE CONTINUED!

 

 

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Copyright AMSynths 2019