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.

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 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 sequences 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.

CSQ100 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.

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 was over four years after the CSQ-100 was launched, but DIN SYNC was a standard in the early 1980’s. I plan to add DIN SYNC in to my CSQ-100 so it can play in sync with my Roland SBX-1 and Cubase.

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.

Testing With the sequencer refurbished it was time to turn in on and check everything worked ok.

Jupiter One

Dusty Voice Card

Introduction  I picked up a Roland Jupiter 4 voice card on eBay in late 2017 in good condition. In June 2018 I started a project to build a complete single Jupiter voice based around this card. The synth will fit into a Moog 60 HP case (another eBay find) with an aluminium front panel that replicates (most of) the controls of the Jupiter 4.

To create a fully working single synthesizer voice means a lot more electronics are required than just the voice card! The complex module controller card has to be replicated along with a LFO. The arpeggiator has been left off the synth as it requires the 8048 micro-controller, which means no programmabilty or presets either. The JP4 modulation capabilities have been retained and enhanced, with a 5-axis thumb joystick and a revised S&H circuit for the VCF modulation.

Voice Card This is an early 1979 D version of the card with a BA662 based low pass filter. The first job was to clean and dry the card and remove the metal guides. This reveals 4 mounting holes for the top of the PCB. The 4 green connectors are replaced with 9 pin SIP headers, so the card can be mounted to a new motherboard PCB. Some of the ceramic capacitors needed replacing and the trimmers will be replaced with high quality cermet trimmers.

A hack to the card to add a potentiometer to adjust the VCA Gain trim has been removed and a trimmer put back on the PCB. The card is spaced 12 mm from the motherboard. I am hoping the voice works, but I am sure there will be some repairs needed. The card has additional power supply caps mounted on the rear, which I have retained.

The card is a Revision D but with Revision E kludges (power conditioning capacitors, 100 and 2200 pF capacitors around the uA726). The FET Op Amps in the card are LF353 rather than TL082, but they exhibit the same low current at 3.6 mA and 13 V/us slew speed, so equivalent performance.

Mock Up

Module Controller The Jupiter 4 has a dedicated 5th card in the card frame to hold all the circuits that translate and mix the programmable CV voltages for the Voice Card. It also contains the CMOS based envelope clock generators. All these circuits have been put on the Motherboard PCB of the Jupiter One which measure 295 mm x 105 mm.

The module control circuits and Noise circuit has been retained, augmented with the S&H from the Jupiter 8 and revised LFO. Op amps have been upgraded to TL072’s and BA6110 OTA chips replace the BA662’s. This PCB is spaced 11 mm from the panel PCB and it contains the +/- 15V power rails, derived from a switched and precision LDO power supply.

Jupiter LFO The LFO in the Jupiter 4 is on the main board and is almost identical to the one used in the Jupiter 8. The JP4 version uses discrete FET switching and a two chip CMOS 2 to 4 address decoder, this is rather component intensive and a simpler approach is needed. I have taken the same approach as Roland did on the Jupiter 8 LFO and used a 4052 analog switch.

4-Way Switch The Jupiter 4 relies on 4-way slide switches which are difficult to source, but we think we have the right one. It may mean making sub PCB’s to raise them up to the right level, but its the simplest electronic solution. The JP4 micro-controller decodes them the 4-way into 2-bit binary signals, using pull up resistors, for use in the Controller and Voice cards, which we can copy for the Pulse Width Modulation, LFO Wave Form and VCF Keyboard Follow.

Panel PCB The front panel PCB is 295 mm x 105 mm and contains 19 slide potentiometers, 4 rotary potentiometers, 2 rotary switches, 11 slide switches, the joystick and 4x jack sockets. The PCB mounts to the Motherboard via a set of 9 pin SIP sockets and headers. It is spaced 11 mm from the front panel.

Joy Stick

Joy Stick The Jupiter One has a small thumb sized 5-axis Joy Stick mounted on the front panel. This controls the Bend (X axis) and LFO Depth (Y axis) with the integrated push switch acting as Gate On. This provides excellent control over 3 of the synths key parameters. The Jupiter 4 Modulation controls (next to the keyboard) have been retained so that the Bend Amount and LFO can be patched into the VCO, VCF and VCA.

Inputs & Outputs The external connections have been kept to a practical minimum to conserve panel space, so this is not a semi modular. There are inputs for CV and Gate, as well as the X and Y CV’s that over ride the joystick if plugged in (Bend and LFO Depth).  The 6.35 mm analog output jack is mounted on the rear of the 60 HP case, along with the 12V AC power supply input.

Missing Controls The lack of micro controller means there is no arpeggiator or presets or portamento. The Trigger Section of the synth therefore has not been included (like the Pro Mars). The transpose switch has been replaced by having a 4 octave range switch.

Commercial Option I may release the Jupiter One as a commercial project using new Jupiter 4 voice cards based on the BA6110 and a BJT expo generator to replace the ua726. DIY and completed synths may also be available. A two voice version is planned (same 60 HP case) with programmable presets and OLED display.

Copyright AMSynths 2019