Roland RS-09 Restoration

RS-09 As Bought

Overview  In July 2019 I acquired a rather worn out RS-09 Mark 1 Organ and Strings machine. Described as: In need of repair and in a pretty bad way, it does make sound but needs some serious attention. I know the RS-09 is not the most versatile of synthesizers with only one or two classic sounds, but it was local and it would test out my repair skills. It certainly was cosmetically very bad although the keyboard was intact despite the side panels being done up with gaffer tape.

History The Roland RS-09 was launched at the end of 1978 (at around £500) and was refreshed as a Mark 2 model in May 1980 to give it more of a Jupiter 8 look. It went on to sell over 10,000 units and was very popular before the DX7 and D50 arrived as a source of polyphonic strings. My broken find is from May 1979 and is the original Mark 1 version with the big switches!

Glue Damage

Front Panel The worse part of this RS-09 is the dramatic glue damage to the center of the front panel, which simply cannot be hidden or removed. I did clean up the panel with IPA and removed the plastic glue with hot water. The panel had been patched up in places with a paint that doesn’t quite match and there is bare metal in a number of places as well as rust spots and scratches.

I could get the panel taken back to the metal, re-sprayed and new screen print but that would be expensive. My decision is to restore as much as possible with a deep clean and a black T-cut and polish.

Power Up I opened up the front panel and switched on the RS-09 not expecting much to happen and I was right, there was no sound from the MONO output. I suspected that all the hard to find parts were dead, like the master oscillator and 2 divider chips. So I measured the master clock and got a rather odd square wave but at the correct 1MHz as it was transposed down one octave. I then traced all the note signals from the master oscillator and everything was working, even the SAD512 BBD’s!

I plugged the output jack into the headphones socket and yes it plays! The MONO jack was clearly dirty or the contacts needed cleaning. I went on trying out the RS-09 and there were actually only a few major problems:

• The TONE slider does nothing.
• The ATTACK and RELEASE sliders cause all sorts of echoing sounds.
• Crackling and breakup of the audio
• One key not working

PSU Recapped

Full Recap At an elderly 40 years old the RS-09 electronics were in surprisingly good condition with no leaky capacitors or major PCB splits, despite the casing being bent out of shape at the rear. It must have had a big drop. There were some intermittent volume problems which I will need to trace and solve, and the Output board had some minor repairs which I wanted to go over, possibly replacing the MIX .

The RS-09 deserved a full recap and that’s exactly what I did, with over 70 electrolytic capacitors replaced with the finest Panasonic (power) and Nichicon (audio) plus the 100nF bypass capacitors (Mylar replaced with MLCC).

VCA and Envelope The unusual effects caused by the envelope generator needed investigating as it was making the RS-09 unplayable, with a click at the start of notes as well as the strange feedback effects. I suspected the BA662 VCA chip, and/or the crude envelope generator. Fortunately the RS-09 Service Manual has a lot of detail about what waveform shapes and levels are expected through out the electronics. This makes it easy to check where the failures are.

The VCA and ATTACK control checked out ok, and I replaced a couple of electrolytics in the ATTACK circuit as part of a wider recap. The GATE and envelope driver circuits worked okay. So my attention turned to the source of the release signal which is the GATE board. I replaced all the 1uF capacitors and cleaned up the PCB and checked for damage. There was a PCB crack near the power supply entry which may have caused the crackling noise. I repaired this with solid wires jumper-ed across the PCB traces. The cleaning revealed a few IC pads in a perilously close position of disappearing, so some careful joint re-flowing was done.

Keyboard The keyboard was in a filthy state and needed a complete clean of the plastic key housings and all the keys (in soapy water). The keys are easy to release, just remember to keep the springs in the order they came off. I decided not to bleach the keys back to white, as the rest of the RS-09 is aged, so it would look out of keeping. There had been some sort of spillage onto the metal base plate of the RS-09 and this was cleaned up, along with cleaning some black gunk one of the key actuators and bending the bronze springs back into the correct alignment.

Op Amps The RS-09 is based around the 4558 Op Amp, and for most of the circuits this is a good choice as its used to manipulate the core waves shapes and act as the BBD LFO’s. The only opportunity for upgrading is IC309 and IC313 which are the BBD input and final output buffers, which I may swap out for a TL072 but the RS-0 sounds fine after all the maintenance.

Output Board Whilst I have restored the output board as much as possible, there are major signs of aging with some PCB traces jumper-ed already. I have cleaned up the jack socket contacts whilst I test the RS-09. I will design and have manufactured a replacement and modern Output PCB using Neutrix jack sockets and an improved Class D headphone amplifier in the future.

More Trouble Shooting After the keyboard cleaning, a full recap was completed and some slide potentiometer cleaning and re-greasing (Deoxit F5 and Fader Grease), it was time to turn the RS-09 back on and explore the RELEASE issue and the missing note. I suspect its a divider problem as the key contacts are fine, however I have replaced all the GATE board capacitors, so maybe I get lucky.

Tone Control Initially the TONE control did not work, it failed to change the tone even though it was one of the better sliders. I measured the resistance and it checks out fine as dual 100KA. I then replaced the old Mylar capacitors (C374,C375) in the circuit with nice Wima polypropylene and polyester versions (250pF and 10nF). I didn’t expect this to work, but it did and the TONE control works perfectly once the pot was cleaned and the new capacitors were fitted.

RS-09 End Caps

End Cap Disaster The RS-09 came with plastic side caps, which appeared on many of Roland’s synthesizers, sequencers and drum machines around 1978 – 1982. Mine were done up with gaffer tape, because all the plastic mountings inside were broken off, except one. There had been previous attempts as repairing the plastic mounts with super glue, but this wasn’t done very well and they snapped off again.

The gaffer tape and glue was removed with IPA, eventually. Getting cap replacements is nearly impossible, and its a challenge to repair them properly so they do not snap off again. I used Araldite glue and supported the plastic mounts all the way along. I did the gluing whilst the keyboard was out of the base unit. I am pleased with the result which is very robust.

August 2019 Update After the full recap of the GATE board and key contact cleaning, 3 keys were not producing sounds. Time to check the key contacts are working for these specific keys. Turns out its the plastic bushing on the bottom of the 3 keys that was not protruding sufficiently to hit the gate springs. This was a simple fix of pulling the bushing down the shaft of the key.

The RELEASE now worked perfectly but the ATTACK was intermittent. I took apart the slider and cleaned and greased it, re-flowing the pot pins stopped an issue when the pot shaft was moved causing a break up of the sound. But the ATTACK was still not working correctly, in fact it was now consistently wrong with a sharp “click” attack. There also seems to be an intermittent problem in the ribbon cabling between the two CONTROL boards. I replaced the soldered ribbon cable with JST sockets and plugs to see if this sorted the issue.

RS-09 and SH-1

RS-09 Tricks The RS-09 has a few tricks up its sleeve to expand its features when used with synthesizers like the contemporary analog mono synth SH-1. There is an external audio input which you can run synthesizer sounds into and get the lush ensemble effect. There is a GATE OUT which is active on every key depression which means you can play a mono synth in parallel to the string and organ sounds, albeit with no CV output. And finally there is a RAW ORGAN audio output which you can run into the analog synthesizer and use its VCF, VCA and ADSR to create filtered paraphonic sounds.

Roland IR3R01 Design & Replica

IR3R01 Chip

Introduction The Roland IR3R01 envelope generator chip was used in the early 1980’s in three key synthesizers; the awesome Jupiter 8, the Juno 6/60 and the MKS7. The chip is obsolete and impossible to locate as NOS, which puts these synths at risk of never being repairable in the future.

The chip is a custom design by Roland which although looks similar to a CEM3310 or SSM2055, it is not the same design. This post is about researching how the chip works, building a simulation circuit (especially for the Key Follow Jupiter 8 design) and finally developing an accurate PIC based replica.

Description The IR3R01 generates a positive going 0 to +10V output signal (maybe less on Juno and MKS) with traditional Attach, Decay, Sustain and Release phases. The chip has CV control inputs for the ADSR phases, as well as the usual gate and trigger inputs, and it always runs from +/-15V power with an additional ground pin. The Attack, Decay and Release are driven by 0 to +5V control voltages whilst the sustain control voltage is 0 to +10V. The CEM3310 uses negative control voltages, so is a long way from being a drop in replacement.

The chip also has a Reference Voltage pin as well as a Common pin, and finally a Modulation pin which is used only in the Jupiter 8 to enable the level of the envelope to be controlled by a CV. Here is the pin out:

1. Modulation Input
2. Attack Voltage
3. Decay Voltage
4. Release Voltage
5. Sustain Voltage
6. Common
7. Reference Voltage
8. -15V
9. Ground
10. Timing Capacitor
11. Output
12. Current Input
13. Gate
14. Trigger
15. Retrigger
16. +15V

Common Pin The input voltage adjusts the timing of the envelope, and a manual trimmer with a Tempco resistor adjusts the attack time maximum, so that all 6 or 8 envelopes have the same timing. On the Jupiter 8 this is set to 6 seconds (although on Page 1 of the service notes its stated as 5 seconds), on the Juno to 3 seconds and MKS 7 to a very short 2.5 seconds. The maximum timing of the Decay and Release is 10 seconds on the Jupiter and 12 seconds on the Juno and MKS. This variation could be due to the increase in Decay and Release CV input resistors from 19k to 22k.

Reference Voltage This is tied to +7.5V (Juno) or +10V (Jupiter) or +5V (MKS). Typically envelope generator chips use this voltage as the highest voltage the attack phase is aiming to, the actual maximum voltage is typically less. Some real world measurements would be useful.

Timing Capacitor This is 68nF (Jupiter and MKS) and 47nF (Juno), this will vary the basic timing of the envelope stages. The manual adjustment of the envelope timing via Common is required because all voices in a polyphonic synth need to have the same envelope times. The adjustment is needed due to variations in the timing capacitor value and variation in chips.

Envelope Oscillator

Modulation Input This is only used in the Jupiter 8 to implement Key Follow, elsewhere the pin is grounded and a different approach is used to implement Key follow in the Juno. In the Jupiter a higher pitch CV shortens envelope time. The IR3R01 circuit is unique with a 28 kHz saw wave being created by a 555 timing chip and sent to all the IR3R01 chips via a buffering Op Amp and a comparator with the Keyboard Follow control voltage.

The IR3R01 receives a 0 to +15V square wave to the modulation pin, which presumably varies in height or frequency to control the envelope speed. It is not yet clear how this works, but it is an important part of the circuit to replicate.

Initial Conclusions The IR3R01 has similarities with the CEM3310 design with a current Input pin and reference voltage, but the control voltages are negative in the CEM3310. The SSM2055 uses positive control voltages and a timing control pin, but no current input. Neither of these chips have the Modulation Pin of the IR3R01. A strong possibility is that the IR3R01 has some basis in the complex Jupiter 4 ADSR which uses oscillators that vary from 10 kHz to 800 kHz, for each of the ADR phases.

The clue is that the ADR front panel sliders on the Jupiter and Juno are non-linear, just like on the Jupiter 4. They have a 4K7 resistor added between pin 1 and 2 to provide a more exponential like CV, rather than getting the microprocessor to do this job. This could be because the ADR voltages in the IR3R01 are controlling the rate of an oscillator, as in the Jupiter 4 design. The modulation pin uses a clocked input to vary the length (not height) of the envelopes, which also suggests a Jupiter 4 ADSR with oscillators. With no IR3R01 datasheet, a more detailed circuit analysis is needed.

Key Follow in JP8

Replicating the IR3R01 There are two uses case of the IR3R01. The simple ADSR in the Juno and MKS where a SMD CEM3310 could be buffered to get a similar “drop-in” response. However a micro controller based design (like Tom Wiltshire’s PIC ADSR here) is going to be less component heavy and potentially could be adapted to the Jupiter 8 use case with the Modulation Pin being used.

By using a digital design the timing will be perfect and the exponential curves can be adjusted if necessary in the data tables, so there is no need for timing adjustment, reference voltage or timing capacitor and these pins can simply be left unconnected. The modulation input needs to be read and the level of the envelope adjusted accordingly. The PIC would need a +5V power supply and most of the input voltages would need reducing (simple resistor dividers?) such as Gate and Trigger, the 10V Sustain CV as well as the 15V Modulation input level.

Whether all this can be done in a 16 pin DIL footprint remains to be seen!

Next Steps I will create a test harness circuit of the Jupiter 8 Key Follow circuit to see what waveform is generated on Pin 1 of the IR3R01 as the Key Follow CV is varied from 0 to +5V.

Replica Design Here are some initial thoughts, I envisage two chips; One for the Jupiter 8 and one for the Juno 6/60, so the envelope timing can be perfectly matched to originals:

1. Modulation Input – create Jupiter 8 test harness to work out what this does – use a resistor divider to read pulse frequency
2. Attack Voltage – read directly and map to correct minimum and maximum times
3. Decay Voltage – read directly and map to correct minimum and maximum times
4. Release Voltage – read directly and map to correct minimum and maximum times
5. Sustain Voltage – reduce by 50% using resistor divider
6. Common – ignore
7. Reference Voltage – ignore
8. -15V – use for buffer Op Amp
9. Ground – use and decouple with +5V
10. Timing Capacitor – ignore
11. Output – Op Amp buffer to increase output to 10V
12. Current Input – ignore or use external resistors with the buffer Op Amp
13. Gate – reduce to +5V using resistor divider
14. Trigger – reduce by 50% using resistor divider or ignore and connect internally with Gate
15. Retrigger – ignore
16. +15V – use for buffer Op Amp and create +5V power for PIC using regulator