The Roland JD-800 is one of those rare digital synths that provides a slider for every parameter, not only is it easy to design unique sounds, but is beautiful to look at too, having an exotic looking sculpted case.
Such art, when combined with a fabulous user interface, comes at a price.
- Keyboard assembly PCB is prone to aging effects.
- If left uncovered, the sliders will collect dust and become intermittent making the synth almost unusable.
- Weak side cheek mountings, plastic becomes brittle with age and easily destroyed even when shipped in a flight case. The synth is becoming rare because so many have been destroyed by shipping.
Guides & Further Information
There are various pages on this site showing details of the Replacement keyboard PCB project.
- JD-800 Keyboard PCB Installation
- U-20 Keyboard PCB Installation
- U-20 Aftertouch Modification
- Roland Keyboard Failure Modes
The primary aims of this project were to:
- Design a high quality replacement flexible PCB for the Roland JD-800 & U-20 keyboard assemblies.
- Fix all the common issues and allow routine maintenance without damage.
- Lower the contact resistance and diode drops to allow old rubber contacts to be reused when properly cleaned.
Roland used the keyboard assembly in many instruments from this era, U-20, D-5, Rhodes 660, numerous pianos for example KR-55 and Rodgers Church organs such as the C550. It was made by Matsushita and was value engineered to the point at which by now they are starting to fail for many reasons as highlighted in this article, Roland Keyboard Failure Modes .
So far we have retrofitted the JD-800 and U-20 with guides detailing the modifications on this site. More will appear as we gradually collect information from users and trial these parts. Unfortunately, there were many different types of Flexible PCB interconnect, so each instrument is not the same with further variations depending on age.
Study & Test
The project has been very long in the making because of the performance study, extensive testing, trialing different contact qualities, old and new rubber contacts. Incorporating enhancements to ease reassembly. 15 instruments were fitted with the assembly using various levels of contact quality and damage. Investigation of how the Roland keyboard scan IC measured velocity and responded to different contact surfaces, was undertaken to better understand the engineering problem.
See page Roland Keyboard Failure Modes for some of the data collected during the development.
It is inspired by the flexible PCB technology used in Aerospace applications, using modern materials and techniques.
Electrically, it was engineered using free tools on Windows and Linux. Although convoluted, was very rewarding once we found a way of generating the definition data, that also contains 8 drawings.
Using Polyimide films and Gold/Nickel contact plating, facilitates high contact performance and a good level of maintainability.
From a cost perspective, using this technology would be out of the question on a commercialised high volume synthesizer product.
The design uses 12 layers of materials, three of which are copper traces on either side of a Polyimide film. Polyimide can withstand high temperatures, making it possible to solder components to the surface and rework if necessary. It has a complicated manufacturing process, taking nine weeks to produce. It is essential to have a good relationship with the supplier and a common understanding of the primary technical goals, otherwise money is wasted working through some of the engineering difficulties.
The end result is shown in the picture below. It was an awesome moment seeing the design come to life.
The picture below shows some of the design features included.
- Gold/Nickel plated contact surfaces that resist oxidisation and can be easily cleaned
- Diodes with a forward drop of 400mV compared with 700mV of original PCB
- Mountings for multiple instrument compatibility
- Key Mold Identification & Contact Placement Guides assist assembly
- Debugging Features: Note & Signal Identification
- Location hole and Keyway for precise fit
Not a Direct Replacement
In the Matsushita/Roland design, there is a thermal connection between the flexible PCB and the interconnect to the transition/main boards. This connection varies between instruments and model year, some even incorporating changes to the orientation of the transition board. For example, in the U-20, the overall assembly is nearly 2m long when including the fragile plastic interconnect. It can be seen in the picture below arriving out of the right hand side.
We opted for a straight FPC interconnect to a transition board for all versions. It minimises cost due to wastage in the manufacturing process. Generally, specialised manufacturers have a maximum flexible PCB length of 950 mm, with most producing only to 450 mm. The FPC and transition board use a Molex 1mm spaced, high reliability gold plated zero insertion force connector. The low cost 2mm nickel plated, push fit type employed in the original design is no longer available.
The transition board adapts the Flexible PCB to the new application, as instruments are adapted, this PCB will change to suit. There are many features of this simple PCB as shown in the picture below.
There are two JD-800 main board connector positions to cover both Type 1 and Type 2 flat cables. Top and Bottom contact options for the Molex connector help with availability and obsolescence. IDC connector header allows the interconnect to be replaced with a rugged IDC cable instead. A flat cable replacement is available for JD-800 and U-20 instruments already. If the mounting bracket is missing, there are 3 holes for mounting the transition PCB to the retaining clip mounting holes using 17mm spacers.
The picture below shows the pieces included with the standard kit for the JD-800.
The main board connector is not attached, it has to be removed from the old PCB and soldered to the correct position depending what type of white flat cable is employed. In the JD-800, there were two variants of flexible circuit employed in the original keyboard assembly, so adds a little complication.
Transition PCB adapts the connections between the flexi and the main board. First transition board versions were only suitable for the Roland JD-800 type 1 flexible circuit and is a “no nonsense fit” due to it’s simplicity. Later version 4 as shown in picture is universal and covers all known options to date.
Finally, a magnetic label is provided to help identify that the flexible PCB has been upgraded should you wish to sell the instrument and get the best price. It can be attached at rear of JD-800 or underneath.
The flexible PCB is fragile and needs very careful handling with clean hands. It’s best handled at the edges.
It is essential that care is taken not to fold, crease or impact the PCB.
Avoid touching the gold plated contacts because contamination is best avoided, it can affect the rubber contact once in place.
Rough handling and impacts from tools can damage the contacts and vias. Admittedly though, we have seen severe damage that didn’t cause issues.
There are minimum bend radius requirements labelled on the PCB, please respect these, even though they are over stipulated; we have tested to a much tighter radius.
It is a good idea to confirm that solder joints are intact on the diodes before reassembly, excessive bending can cause joints to fracture.
Maintenance & Repairs
Cleaning and maintenance are easily possible.
To be able to perform routine cleaning of keyboard contacts is considered essential, especially if it is used in a high dust/damp environment. Contact plating is 3 um thick and resists cleaning with IPA. Do not use abrasive paper or cutting polish to clean the surfaces, otherwise plating will be removed rapidly.
If plating has been accidentally removed, or the contact surface is uneven due to extreme damage and giving problems, it can be repaired by using silver based conductive paint found in membrane keyboard contact repair kits.
Polyimide film is temperature resistant and can be soldered by hand as long as it is performed quickly. Hot air can damage the vias, if replacing a diode, use two irons to melt contacts simultaneously and brush it off. It is a good idea to drive out moisture before major soldering work, by warming the PCB in an oven at 70 degrees Celsius for one to two hours.
The picture below shows an extreme situation, where hot air had damaged the nearby vias when changing a diode. They were then subsequently re-linked, using 30 AWG Kynar coated silver plated wire, typically used for prototyping using wire wrapping. This flexible circuit has been on test for a considerable amount of time in an instrument.
Before soldering, ensure that rubber contact avoids touching the planned soldered area, any solder contamination will oxidise and prevent correct velocity pickup.
Contact plating is ENIG, a Nickel and Gold combination that gives a higher resistance to corrosion and can be easily cleaned during routine servicing. The gold plating sometimes has a matt finish or patches which is acceptable and is only caused by an matt copper surface underneath. The picture below shows the typical consistency of the finish.
The design is robust enough to deal with contact imperfections. We have conducted extensive tests on various levels of damage, from bending to harsh creasing. Below is a typical cosmetic imperfection on S6 that has no effect on performance, it is still working after a number of months.
Contact surfaces of varying quality are shown in the picture below. This PCB was rejected on a purely visual basis, S61 was extremely creased. For some reason 15% of the batch had S41/42 impacted in exactly the same way, indicating something common in the manufacturing process. All visual and electrical test data is fed back to the manufacturer and updates to build instructions are made. This is why this project has been long in development, electrically, the PCB is very simple but the processes of manufacture have to be trialled and worked out as well as address any training needs.
On this rejected PCB, we added further damage in different ways to try and spoil the performance. Even with this level of damage, they work perfectly. Using this in a test instrument, gives confidence in the design.
We try our best to prevent cosmetic defects during manufacture, but if users accidentally damage the flexible circuit, they can be recovered by careful manipulation, silver paint contact coating or just left alone. Contact us with photographs, for advice should it be accidentally folded. There are techniques using a little heat to recover them.
One positive aspect that we have discovered is that old rubber contacts work perfectly, provided they are adequately cleaned and dust free.
We have successfully trialed damaged and worn contacts with a great deal of success.
It is important to try and not damage too many fixing pillars when removing, they help keep the flexible circuit flat and prevent dust from entering the contact area.
Check out the technique in the Roland JD-800 Keyboard PCB Installation page as shown in the picture below.
Finally, check out our favourite cleaning method for rubber contacts in picture below. Fresh brush head, on a Sonicare toothbrush under running water. We have had a lot of success with this method. It removes dust and human debris very well. They can be finished off with some IPA on the contacts but we didn’t need to on instruments we evaluated.
Copyright © 2021 Super Synth Projects, Guy Wilkinson