This is a general purpose keyboard assembly guide covering all instruments for the common components in the keyboard frame.

Servicing a keyboard  assembly is a filthy business in many cases. Often, synths are stored without dust covers or have been gigged and the build up of FOD can be disgusting, especially when combined with Roland manufacturing over zealous lubrication. This dirt is a hazard for the keyboard contacts and is to blame for many of the issues. See Jorick’s refurbishment article to see how challenging it can be, he made an overview of this installation process too.

Issues can also occur if it is simply the case that the keyboard has rarely been played, oxidisation of contacts over time happened in our case.

Ensuring Success

This page is meant to supplement the Roland service notes when installing the replacement Flexible PCB into a keyboard frame, it is mostly concerned with important points that ensure success and reliability. For example, the JD-800 Roland Service Notes can be downloaded from an excellent no-fuss site www.synfo.nl, please make a donation if this site is useful to you.

The keyboard section of the Roland Service Notes is pretty thorough in it’s explanation. It gives plenty of warnings and tips on disassembly and reassembly.

As a whole, the keyboard assembly is quite complicated and contains many parts.

Read this guide fully before embarking on the disassembly and repair of the keyboard assembly.

We now have an extensive troubleshooting section in this page, please use it to help understand and identify issues before contacting us.

Mistakes That People Make

We are here to help but don’t be alarmed if it doesn’t work first time, these are the common mistakes made during installation.

• Not removing microscopic dust particles or red glue from the rubber contacts.
• Not brushing off dust from the new flexible PCB.
• Touching the silicone lubricant on the assembly then touching base or top contacts.
• Not handling the assembly by the edges and transferring finger grease to the contacts.
• Fitting flat cable connector to the wrong position
• Installing white flat cable between transition PCB and main board, upside down at either end.
• Not removing residue after cleaning a contact with IPA, this is done using a dry lint free cloth or bud.

Cleanliness

Cleanliness is essential when fitting any keyboard contact PCB, the most common issues that cause problems in priority order are:

• Dust
• Oil on particles from hands and fingers
• Red epoxy glue used to secure weights in the keys (Roland batch issue)
• Silicone grease contamination

See our special page for an exhaustive examination of failure modes.

The new flexible PCB is thoroughly cleaned before shipping, but it will have traces of dust that must be removed before assembly using a brush or lint free cloth.

Interestingly, the studies have shown that a large proportion of issues of the original flexi are simply contamination on contacts.

Rubber Contacts

It is essential to thoroughly clean the rubber contacts or source new and remove dust particles before reassembly. Cleaning new contacts can slightly deteriorate contact resistance however it is still essential to remove traces of dust using an anti-static brush.

Dust causes uneven velocity pickup, or occasional mis-interpretation of velocity on one or more keys.

Red Glue

The red glue can be removed by soaking the keys in hot caustic soda solution used for cleaning drains. Take care not to let the solution exceed the melting point of plastic, there are reports of warped keys. It is a pretty nasty process but yields good results. There are various guides and forums on the web that detail this process, one of which is here.

Thoroughly cleaning all parts of the keyboard assembly is strongly recommended.

Caution

To fit a keyboard assembly, soldering and de-soldering skills are needed. We can solder the main board connector on the transition board for you, let us know what type of flexible circuit you have when you order or send a photograph of the left hand side of the keyboard where the flexible circuit exits the assembly.

Key Retainer Strips

Great care is needed when removing the key retainer strips, they are impossible to replace and easily broken because they have break off points.

We do have a suggestion in a later section for how they can be replaced with plastic strips, but it is a poor substitute.

The example shown below is for a D-5 keyboard frame and a flat blade screwdriver is used to work under them gradually peeling them off. It can be seen that we narrowly averted breaking the first position! With care, the old adhesive can still be used.

Note the order in which the strip under notes 49 to 61 come off, there are markings for “LOW” and “HIGH” molded into the plastic. “LOW” was installed at note 61 on our instrument. We are not sure if this is important but we put them back into same positions.

Springs

If the keyboard assembly is already clean and rid of red glue, a useful technique for keeping the springs in place whilst working on the assembly is to use a strip of wood and two self tapping screws to hold them in place. On the JD-800, bracket for the transition board has to be removed first.

Care must be taken not to get silicone grease on critical parts such as electrical contact areas but if careful, can speed up fitting considerably.

Flexible PCB Removal

Plastic Rivets

Rivets are a 2 piece part, simply pull the head out and the other part can be removed easily.

Flexible PCB

Remove the flexible PCB and clean the metalwork underneath, there is usually oil contamination under this area. Removing with a tissue is sufficient.

Rubber Contacts

Removal

A great technique for removing contact strips is by using a silicone sealant tip that has been trimmed so that the hole is 2.8mm wide. The tip is dipped in water to make the surface slippery before applying to the pillar. The contact is pulled very gently from the opposite side, whilst wiggling the sealant tip. Take care not to use much force, a gentle pull is all that is required and the pillar will gradually pop out. If more force is needed then it is because the tip is not aligned with the hole in the metalwork or you are pulling the contact at an angle and not straight out.

This technique was inspired by a beta tester, Carsten, who used a trimmed tip from a de-soldering hand pump. The PTFE surface meant that water was not essential.

Broken Pillars

Mounting pillars often break off when contacts are removed by just pulling them out, if the instrument has been serviced before, it is likely that they have been damaged.  When some of the rubber contact strip mounting pillars are missing, it can lift up a little during play, allowing dust to work it’s way under and eventually prevent a from contact working. In this case, simply using a keyboard cover when not in use prevents issues. The design can cope with some of these missing provided that the contacts lay flat. If there is a ripple on the flexible PCB adjacent to a missing pillar, it can cause minor variations on velocity pickup for that key. Some users have placed a small piece of double sided tape close to the area under the flexible PCB, to correct the issue. If doing this, ensure PCB is correctly positioned.

Cleaning

When using old contacts, They must be cleaned thoroughly before installation. This can be done by soaking them in a hot solution of washing liquid. Take care to rinse off thoroughly. If contacts are free from red glue, we prefer using just running water and a Sonicare toothbrush.

Once dry, clean with IPA followed by removal of IPA residue with a dry bud. Any remaining dust and filaments from the bud can be removed with an anti-static brush. At minimum, removing dust and cleaning with IPA is essential.

When using new contacts, it is a good idea to check and remove any dust because handling of these items can be questionable if not from a Roland distributor.

Contamination

The contact surface is flexible thus allowing for some dust contamination, but it is the build up of dust over time that adds to the problem with velocity pickup. It is best to remove all visible traces of dust before fitting the contact strip. Using an anti-static brush really helps achieve a dust and particle free contact.

The most damaging areas of contamination are:

• Red epoxy glue that has gone soft and run into the assembly.
• Oils from skin particles and dust.
• Lubrication employed on the key mechanism.

Red epoxy glue that wasn’t properly mixed with hardener affected a huge number of instruments for a specific time period of manufacture.

Silicone grease that migrates or gets transferred by dirty hands adds an insulation layer that easily spreads over the contact and penetrates the carbon impregnated rubber contact.

Roland used automatic dispensing of lubricant and too much was used so it becomes a hazard to the contacts when servicing.

There are many “solutions” for contact improvement, many involve adding aluminium foil or conductive paint. However these “fixes” actually add to the problem by either preventing flexibility and reducing ability to cope with dust or worse still; adding a metal adhesive backed foil such as aluminium, causes excessive bounce that confuses the scan chip or oxidises over time and prevents low current contact.

The amount of current that passes through the switches is approximately 450 uA at 4.3 V, this is not enough to reliably break through a thin Aluminium or silver oxide layer that can develop later.

For best performance, a resistive top contact is necessary for the contact de-bounce function and not confuse the keyboard scan chip.

A solution involving carbon top contacts and gold bottom contact is the most reliable method.

Flexible PCB Placement

When unpacking and handling, take great care not to fold the new flexible PCB, otherwise permanent distortion occurs that may be difficult to correct.

Place the flexible PCB on the keyboard frame whilst avoiding touching any contacts or contaminate them with dirt or fluids.

Move the PCB such that the Primary Location hole between contacts S25 and S26 sits over the bump in the keyboard frame. Align the flexible PCB such that it is straight and locates over the other location bumps.

Once happy with alignment and primary location hole is firmly in place, apply some insulation tape to hold in position. Before applying the tape, ensure that the surface is clean and free from grease, remove with IPA if necessary. The lubrication used on the keyboard assembly is silicone based (safe on plastics) and very difficult to remove. If this lubricant reaches the contacts, they will stop working properly.

Checking & Cleaning

Carefully inspect the flexible circuit for any signs of contamination:

• During handling, touching the contacts accidentally can deposit oils from the fingers.
• Lubricants used on the keyboard frame and moving parts can fall onto the surface during positioning.
• Although unlikely, flux residue can be present from the manufacturing process.

If contamination is present, or if in doubt, clean each contact with a cotton bud or Q-tip soaked in IPA before immediately drying off with a dry bud to remove all traces of IPA residue. It is very important that all contaminants are removed before assembly as it is a very long process to correct later. Any adjustment means the keyboard will have to be completely disassembled and rebuilt.

Removing Static Charge & Dust

Polyimide film used in the Flexible PCB is prone to carrying static charge and therefore can attract dust particles during assembly that could ruin performance.

Using a clean anti-static and conductive brush, remove the surface charge plus any dust. Take great care not to place the brush on the metalwork or other areas that may be contaminated with lubricant or dirt. It is recommended to clean the brush with IPA before performing this operation. Brushes like this are often supplied with ESD handling kits and are very low cost on eBay.

Fitting Contact Strips

Contacts must be free from dust before fitting, use the anti-static brush to remove all particles & filaments. The new Polyimide film is prone to rippling due to the manufacturing process, once contacts are in place it is pinned down and held flat. To prevent misalignment, start fitting contact strips around the location hole. There is a mark on the flexible PCB that indicates the edges of the rubber contact strip. Once first contact strip is in place, check alignment of the flexible PCB and adjust as required. If old contact strips are used, clean with IPA then brush off the cotton bud filaments left behind.

The Roland Service manual recommends a paperclip to engage the contact pillar, however this can be an issue especially for old contacts where the rubber has hardened. Either push very gently or use method as we do below.

One user has recommended not using a paperclip to reinstall the rubber contacts. They always put the rubber dome in the hole and keep pressure on it with a finger. Then with two fingers from other hand, gently pull it through the hole until it pops into place. If using a paperclip you can very easily punch a hole in the rubber or rip the dome off.

Fit the second contact strip to the right of the first one.

Fit all remaining contact strips making sure there is no dust of contaminants on the contact points. Once all contacts are in place, they are protected from any dust particles.

PCB Clamp

Using the original plastic rivets and plastic bracket, secure the flexible PCB to the metalwork. It is very important to insulate the sharp metalwork edge from the new PCB. If this was removed, replace with insulation tape. If the plastic rivets have broken or missing, two M3 bolts, nylon washers and shake proof nuts are used instead. If using the bolts, do not tighten, they must be slightly loose so that they turn freely to prevent crushing the delicate conductors in the PCB.

For instruments such as the U-20, additional plastic is required to prevent short circuits and damage, see appropriate guide for information.

First Optional Trial

It is recommended to try the keyboard assembly continuity before fitting keys by plugging in the keyboard assembly, putting synthesizer into test mode and pressing the tops of the rubber contacts to confirm basic functionality.

Fitting Keys

When fitting keys, it is common practice to lubricate moving pivots with silicone grease. If doing this, use a very small amount of grease, too little is better than too much. This is to prevent it spreading around over time and eventually reaching the contacts.

Do not use petroleum based grease as this will damage the pivot point in the plastic key and it will split over time. It also gradually evaporates oils that can enter the contacts.

We prefer to install all black keys first, it makes for a faster assembly time overall. When fitting all keys, make sure that they are properly engaged. It is easy to do with version 3 flexi as it has the key numbers marked with “#”.

Whilst fitting the white keys people have noticed that the gaps between the keys can be uneven and they have to move them around to make them look aesthetically pleasing. Maybe keys from particular mold numbers have to be grouped together, but we haven’t tested the theory yet. The mold number is indicated by the second two digits marked on a white key after the letters.

It is best not to fit the locking strips underneath the keys at the pivot points until the assembly is properly tested and you are happy with performance / alignment. Handle carefully as keys will become dislodged easily.

Flexible PCB Connection

Once the Transition PCB has been fitted as per the guidelines for a particular instrument, the next step is to connect the flexible circuit. On the transition PCB Prepare the ZIF connector by opening the latch. Pull on both edges very carefully to open the slot.

Insert Flexible PCB connection into the ZIF connector and simultaneously pinch both latches to lock in position. The cable will flip up and down slightly as this is performed.

Guide Arrow

If you have a flexible PCB with a guide arrow, apply very small pressure in direction of arrow whilst locking the first side at end of arrow, to remove play and assure perfect contact registration. Reason is given in Troubleshooting/FPC Alignment section.

First Trials

Once all keys are put back in place, the next stage is to attach the keyboard assembly to the main board and test as per the instrument fitting guide. 

Testing is best performed using test mode in the synthesizer. The best way to test is to compare pairs of notes with different velocities and gradually work down the keyboard.

Please go back to the fitting guide for more detail.

Trouble Shooting

After performing troubleshooting with rubber contact strips removed, be sure to remove any remaining dust and contamination that may have happened during this time.

When probing contact areas, take care not to scratch or damage the plating.

Poor Velocity Pickup

The first contacts that are made, top row marked “BR”, are very sensitive to contamination because they determine the critical timing start point for the velocity measurement. Any bounce or high resistance caused by contamination or dust can prevent consistent operation.

If the “BR” contact is not seen then velocity will be deemed “maximum level” when “MK” is made thus resulting in a false impression that the keyboard is “working” for many types of patches. Use test mode or choose your patch carefully when testing.

The most vulnerable points are where rubber contact strips mate with each other, as shown in the example below where dust and fluff affected the top contact resulting in velocity measurement that appeared to be “high gain”.

The keys could easily be removed in that section because the locking strips had not been installed, then contacts cleaned again. Unfortunately we used “cotton buds” that can leave cotton filaments behind, but we had nothing else and extra care was made to ensure it was clear afterwards. The anti-static brush was used to remove traces of dust.

Keys that require a group of contacts removing can be dealt with by another method. In this case, the velocity pickup issue was only slightly inconsistent and grease contamination was suspected. A strip of extremely high quality paper that doesn’t release fibers was used (high density photocopy paper). It is placed carefully in between the contacts and flexible circuit, whilst avoiding any grease contamination from the springs.

The paper was wetted on an inch of it’s length with IPA.

Then drag the wet area underneath the contact whilst pressing very gently. Be sure to drag a dry section to remove IPA residue.

The other methods involve removing the rubber contact section again, which is time consuming.

Key Groups or Intervals Not Working

The possible explanation for this condition is as follows:

1. Bad Contacts – Worn or permanent red glue damage
2. Factory Reset Needed – Synth remembers shorted buses from previous bad PCB
3. FPC Alignment – Change placement of FPC before locking
4. Open Circuit Traces – A disconnect in any of the traces & flat cables

We have had reports of 1 & 2. Items 3 & 4 have not been reported but are included to aid understanding if debugging needs to be performed.

Before confirming continuity issues between contacts (BRx / MKx) and diode commons (Tx) to the marked out test points on the Transition board it is worth confirming if the FPC is installed and aligned correctly.

FPC Alignment

When unlocked, you will notice that there is play between edges of FPC and connector slot. It may be necessary to move and relock to achieve better contact registration. Picture below shows registration marks made by the connector when installed and removed. By observing these you can check and using the play, adjust if required.

The Molex connector is designed for mass volume production using reflow ovens where shrinkage of plastic is accounted for in the specification of the FPC. Due to the low volume nature, we can only hand solder or hot air reflow, so the connector slot doesn’t shrink to exactly 25 mm. When the FPC is on edge of tolerance (as specified by Molex), registration can be slightly out of spec.

Molex connection tolerance is impossible to control for a low volume product.

This aspect is checked and tested at extremes of movement before build, test and shipping. To account for it on some flexible circuits, we have drawn a guide arrow on the FPC to illustrate that the optimum position is hard over to one end. These units are at an advantage because registration at center of contact is assured and confirmed.

Flexible PCB Continuity Issues

If continuity issues between contacts BRx / MKx and select lines (diode commons) Tx are suspected then they can be easily tested with a continuity tester. The picture below shows the markings and areas that can be used to verify the electrical circuit between the flexible PCB and the Transition Board.

Precautions

• Do not perform continuity tests whilst the mainboard is connected to the Transition board. Remove flat cable end from mainboard.
• Take care not to damage contact plating with probes or tools

It is a simple matter to check these connections, in the pictures below, left hand is confirming BR0 switch contact group bus and right hand shows confirmation of select line T1 on Diode D1 common. Continuity issues will affect multiple keys or groups of keys.

Checking the flat cable for the JD-800 keyboard assembly is a similar simple process as shown below. It is also similarly applicable to other instruments but with different cables.

 

Single Key Failure or Multiple Triggering

Diode Checks

Faulty diodes when short circuit can result in multiple key triggers, when open circuit, keys not working. Static electricity during a problematic installation can cause damage during install too. In one report, a user suggested that a diode was faulty so we came up with these test steps, although we discovered that red epoxy glue was still present on a rubber contact. 

Here is a simple technique for checking a suspect diode.

Solder Bridges

Inspect carefully for solder bridges if you have fitted the connector yourself. When we supply a soldered connector the whole assembly is tested end to end with our test equipment.

Adjacent connections can also be easily checked using test points on the Transition board but be sure to disconnect the mainboard whilst performing checks. Picture below shows two types of solder bridge that can cause multiple triggers.

It is also a good idea to confirm that the Molex SMD connector pins are free of solder splashes.

Final Reassembly

Once happy with performance, the keyboard assembly should be removed and the Key Retainer Strips are put back into place with double sided tape. The plastic locking strips have shallow teeth that sit in each key hole. In the picture below a flat ended tool is used to push them into place rather than press with a finger 61 times!

Strangely, every keyboard assembly we have seen that has been through a UK tech, has these missing. If not present, the keys will fall out easily!

The picture below shows a U-20 that didn’t have any key retainer strips, someone had been tinkering before and done a pretty bad job of everything. Some 5 x 1.5 x 250 mm plastic strips were sourced from eBay for £3 and double sided taped in place. Not ideal, but better than nothing as they help prevent keys falling out too easily. Brass strips are more readily available but if they become detached then short circuits could occur and cause a catastrophe/electric shock.

Refitting

In all instruments it is necessary to ensure that the surface of the flexible circuit does not touch metalwork or printed circuit boards, for example in the picture below for the JD-800, early flexible circuits touched the metalwork and some tape was used to prevent short circuits.

Secure the keyboard assembly in place and retest before putting the synthesizer back together and re-test.

 

Copyright © 2021 Super Synth Projects, Guy Wilkinson & Jonathan Williams