Roland S10 OS Modification

Only half a display

Introduction I fitted a new OLED display to my Roland S-10 sampler in February 2019, but the new display only shows the first 8 characters, as the original display is configured as 2×8 lines when it actually shows 1×16 lines. The new display is not a drop in replacement. This problem also affects the Roland Alpha Juno 1 and 2 which uses the same display. The solution is to modify the operating system to change the assembler code that writes the characters onto the LCD.

Processor History Roland started off in the late 1970’s using the Intel 8048 processor with inbuilt mask ROM in the Jupiter 4, Pro-Mars, CSQ sequencers and the 184 keyboard. This had a tiny 1k byte of ROM space, so the programs had to be very small and tight! The Juno 6/60 used the 8049 which has double the ROM size, whilst the Jupiter 8 and MSQ700 use the Z80 and external ROM chips. By the mid 80s’ Roland were using the Hitachi 630X processor family alongside the Intel 8051 family. The S-10/MKS100/S220 samplers all use the same Intel 8032 processor with 64k bytes of external ROM to hold the operating system. The UV EPROM chip used was the MBM27C512.

OS Change Process To correct the display readout I need to modify the code in the Roland S-10 Operating System which is written in 8051 assembler. Fortunately this has been done before to alter the MIDI notes off (in both the S-10 and Alpha Juno), so I am treading a proven path. The OS is extracted from the ROM into a binary file, then disassembled. I can then alter the display code to provide the corrected offset on the LCD, and assemble the code back into a binary. This can then be burnt into a new EPROM and put into the S-10 replacing the old OS chip. I am using a modern Micro Chip 27C512 chip with 70 ns read speed, and they cost £1.50 each.

Roland S10 OS Binary The latest OS version from Roland is 2.07 file, and this ROM has already been extracted and is available here. I used this version as it saved a step in the process and meant I could look at the disassembled code quicker, and see whether the project was possible.

OS 2.07 Features I suspect most S-10’s have the latest OS, but if you have an earlier version this is what you are missing:

  • MIDI system exclusive capability.
  • Fix to fast appregiations dropping notes.
  • Fix for the GATE input silencing voices.

Disassembly I tried using a free Windows program from Spice Logic to disassemble the code, but this did not read the hex file successfully. I then used a Windows 10 cloud based disassembler and this gave me both a reference and disassembled file. Looking through the code I could see what looks like an LCD write subroutine at address 73C3 with two sets of mov instructions spaced 40h apart, which matches the spacing of the original LCD data structure. Here is the code:

Address_73C3:
mov a,#0x80
mov Register_68,a
mov P2,a
mov r0,#0x00
movx @r0,a
inc r0
clr c
lcall Address_3AE0
lcall Address_78ED
mov r0,#0x00
mov a,#0xC0
movx @r0,a
inc r0
lcall Address_3AE0
lcall Address_78ED

In theory all that needs to change is the second mov command to use an address of 0x88, so that all the 2nd line display commends have an offset of 8h in addressing rather than 40h. The code would be well written if all the LCD calls use this sub routine. Register 68 looks like the LCD display register. There are around 200  text messages in the S-10 operating system, including messages for the test routine, and an Easter Egg at address DB7E (SUZUKI GSX-R 400, HONDA INTEGRA GSI). This text is longer than 16 characters and was never displayed!

I have mapped the text messages in the code to the address lines, and then back to the LCD write sub routine at 73C3. I have not mapped them all back but I am sufficiently confident to change the code and burn a new EPROM along with a change in OS version to 2.09, as 2.08 is the unofficial modified version for correcting the all MIDI Notes Off.

Assemble and Burn The change is only two bytes in the whole code, so my initial approach is going to be to alter the binary code at the appropriate addresses rather than re-assembling the disassembled code, as this is more straight forward and the as51 assembler may not read the disassembled code correctly. The first stage is to buy some EPROM chips (Micro Chip 27C512) and burn the 2.08 code into one and check the S-10 works with no modifications by me.  I am using my trusty TOPS 2009 ROM burner, but there are more recent versions that do the same job.

The second stage is to modify the binary code in two places (OS version and LCD offset), then burn a new EPROM and see if it corrects the display writing on ALL 200 messages. If there are any exceptions I will go back to my message address map and see how the display is being called for that message that fails. I will post the results soon!

 

 

Roland S10 Sampler Refurb

Introduction In February 2018 I bought a Roland S10 sampler for £50, which looked in reasonable condition on eBay but with the usual QD drive failure. My plan was to re-use the 4 octave keyboard in another project, as S10’s often have had a hard life! However once I had cleaned up the sampler at home, I found it worked well except for the drive, so I decided to keep it as a sampler in my workshop and restore it back to the best condition I could by replacing the worn out components. The sampler may have been bought and used by J-M-J originally, so it seems a good idea to save it.

This post details the refurbishment work that has been done.

History The 12-bit S10 keyboard sampler was introduced in May 1986 at an initial price of £1099, and sold strongly in 1986/7 with over 8000 manufactured before it was phased out with the arrival of the 12-bit S330 in early 1988. In February 1988 the S10 was was being blown out at £699 and the S10 was one of the cheapest ways of getting into sampling, albeit just 4 seconds and with a really unreliable storage drive. The S10 and its rack mount brothers the MKS100 and S220 have fallen out of favor with musicians and can easily be found secondhand for under £100, they are actually quite usable and immediate.

Old LCD Display

LCD to OLED The 16×1 blue back lit LCD had faded significantly (as expected) with the EL reaching end of life and the inverter whining. Take a look at the picture, hard to use a sampler with a faded display with just 16 characters!

This was the first component to be replaced on the S10. I used a modern OLED display which provides a much clearer display and wide viewing angle. There is no need for a contrast adjustment.

The OLED I fitted is the Vishay O016N001AGPP5N0000, which is the correct overall size of 80mm x 36mm and has a green character colour. I bought it from Mouser for £13. It is an easy fit once the main front panel has been removed, and the LCD holder unscrewed. The inverter cabling to the power supply and inverter are removed, and the LCD cable desoldered from the old display and moved to the new display. The contrast cable wire is not required and should be removed (it did go to Pin 3 on the display).

New OLED

The new display works fine but only displays the first 8 characters, just like the Alpha Juno displays upgraded to 16×1 OLED’s. The solution is to hack the operating system which is fortunately on a separate ROM chip. All the 2nd line display commends have to be revised to use 8h in addressing rather than 40h.

I want to keep the OLED, so a firmware hack has to be done! The OS code can be downloaded as a binary and I now need to reverse engineer it. The firmware for the Alpha Juno has been successfully hacked to use a modern OLED, so I will follow the same route and disassemble the binary into the source assembler code. Then make the change , assemble and create a new ROM.

I will post progress on this and the final ROM code.

Old (L) and New (R)

Panel Switches Some of the button switches were a little unresponsive after 33 years, so I bought a complete new set of 30x from Mouser. This is much cheaper at just £5 than using eBay. The Alps part number you need is: SKHHAMA010.  I clipped off the old switches, desoldered the legs and removed the old solder, then soldered in the new switches making sure they are flat against the PCB’s. I removed and cleaned the PCB’s along with button caps. If you need switches for the MKS100 or S220 they are Alps SKHHBSA010, also available from Mouser.

Panel Buttons Two of the buttons were badly damaged, still usable but I have replaced them with NOS items. A bit expensive but worth it.

Keys A couple of the white keys had minor damage, a visible cigarette burn melted into the top surface and a black spot of corrosive paint to mark the upper split point (why?). I was able to tidy these up with a craft knife and some sandpaper, so I did not need to buy replacement keys. All the keys had to be thoroughly cleaned with soapy water, as they were filthy, I use shower glass cleaner.

Two of the keys did not work, so the whole keyboard has to be removed and the contacts cleaned.

Slider Dust Cover The S10 has a dust cover for the 3 slide potentiometers to the left of the keyboard. The dust cover had perished and looked awful sitting in front of the sliders and visible through the plastic bezel. I cleaned the slider and bender plastic bezel after removing it from the sampler, and removed the bend lever (to clean it) along with the PCB. I could then remove the old dust cover, which is a push fit, and copied the outline onto a new one cut out of 2mm neoprene sheet. Quick refit of the parts and… Perfect and it looks much better!

New Lithium Battery

Battery The 3V lithium battery needed replacing after 30+ years, as on power on the Performance Data was lost, and a message came up on the LCD requesting the Bender range be entered. The battery is on the main PCB but tucked under the keyboard, so that had to come out! The old battery measured 3.29V, whilst the new one measured 2.94V, do not be fooled, a 30 year old battery needs to be replaced! A new battery was bought off eBay and soldered in. The old and new battery soldering can be done (carefully) with the PCB still mounted in the casing.

Power Supply All the large and small electrolytic capacitors on the power supply PCB were replaced with new high performance versions with the same pin out and dimensions.

Disk Drive  The disk drive was in good condition with no motor whining but it failed to load QD disks. I took the drive out and it was immediately obvious that the belt had perished. I ordered a new drive belt from eBay (Germany) and in the mean time removed the old belt goo with isopropyl alcohol and cotton buds. The new belt was fitted and the drive worked perfectly after a few issues reading it settled in and worked.

Disks The S10 sampler came with 16 Quick Disks in various conditions but only the 3 newer disks were readable and the rest were thrown away.

S10 Manager I downloaded this software onto a Windows 7 PC and soon had it working well with the S10 (and S220’s), making sample transfer easy. I spent an evening working through the factory library, the JP8  Brass & Strings is the high light!

 

Roland S220 12-bit Sampler

Introduction In October 2018 I bought a 31-year old Roland S220 sampler for £70, with no photo of it working this was a bit of a risky purchase! Why buy one in the first place, given it only manages 4.4 seconds of sample time at 30 kHz and 12-bits? Even the disk drive is horribly unreliable and impossible to replace or even find blank QD diskettes for.

Well its that 12-bit lo-fi sample sound that I am after, so I can sample some modular synth sounds and create bass lines and strings. I also want to develop a Quick Disk drive replacement using a microprocessor, which will store 100 sample banks in memory.

Worn Out 16×2 LCD

History The Roland S220 was introduced in September 1987 as an upgraded 16-voice version of the S10/MKS100 but with the same limited 256k byte RAM. It lasted about a year in production before the improved S330 was launched with 756k byte of RAM, so its a relatively rare sampler. The S220 received a new operating system with a lot of improvements over the S10 including 4-part multi-timbrality and up to 4 audio outputs and a good auto loop. There is an external trigger and arpeggiator, so it plays nicely with modular synthesizers.

My S220 I bought a new mains lead and carefully powered it on, after checking there were no internal issues such as damaged power caps. It booted successfully but the LCD screen was extremely worn out and barely visible, so a new green 16 x 2 OLED display from Raystar Electronics (Part Number: REC001602AGPP5N) was bought for £22. You can buy the OLED in different colours, all part numbers start with REC001602A and they are the correct 80mm x 36mm size.

New OLED

New OLED Display It is a simple swap, the new LCD is the same size as the new OLED, and the EL back light power can be disconnected from the power supply. The front panel has to come out to gain access to the LCD, and the interface wiring has to be desoldered from the old LCD and re-soldered to the new LCD without pin 3 connected (no need for contrast).

This is easy to do as the wiring unplugs from the motherboard. The OLED needs careful alignment with the front panel bezel so all the top and bottom of the characters can be seen. The character size of the new display is slightly larger, notice the tight fit of the lettering.

Roland L-109

Sample Disks I also bought a set of new Roland sample diskettes, the L-109 Synth & Organ, as it has a rather nice Jupiter 8 and VP330 sample bank. This loaded successfully on the second attempt after I cleaned the disk head and felt pad. Amazingly the QD drive works, although it is easy to do sample bank transfers over MIDI using the S10 Manager software.

Second S220 A couple of weeks later I bought a second S220, but this was in much worse condition . The electronics seem okay but the QD motor was permanently on and whining loudly, and the drive belt had melted. I did manage to reduce the whining and improve the head tracking but the Motor will not stop when powered on. So this S220 will be the “mule” for the QD drive replacement project.

Maintenance The lithium batteries were replaced in both samplers, they keep power to the 8k bytes of Performance Data held in SRAM. A symptom of the battery failing is that the Bender range setting needs to be input at power on. Don’t believe the voltage measured on the battery, even if its above 3V replace it. The old battery legs can be cut away and the new one soldered in place without removing the PCB.  The power supplies were refreshed with new electrolytic capacitors, especially the 4700uf and 2x 2200uf reservoirs as they have been working for 30 years, along with a lot of cleaning out of dust from the casing!

QD Drive Replacement  Part of the reason to buy a Roland S220 was to design and produce a QD drive replacement. The QD drive uses a single spiral track recorded onto each side of the diskette, and is half like a cassette and half like a 3.5″ floppy drive. It transfers data slowly at 100 kHz and is encoded in MFM format with 64k bytes each side taking about 5 seconds to load. Samples can be loaded and saved but also the disk can be read to provide the sound name and bank setting.

The drive replacement will use a micro-controller to read and write the data, a small OLED display and a SD card for storage. This project will take place in 2Q19 and it has its own dedicated web page here.

Copyright AMSynths 2017