KEYBED ISSUES/CONSTRUCTION
Disclaimer: This FAQ is not intended as a maintenance or service guide for Fatar keybeds. Nord expressly DOES NOT encourage Nord owners to open up and fiddle about with the inner workings of their instruments, and doing so will invalidate warranties. Rather, this information is offered so that YOU, Nord owners, can have a better understanding of what is going on inside your instruments. Hopefully, this FAQ will not only provide you with guidance in keeping your Nord in better operating condition, but if/when problems do arise, you can have a greater comfort level in the knowledge that such problems are relatively trivial and easily (usually) corrected by a qualified repair tech.
FATAR KEYBEDS
Nord uses exclusively Fatar keybed mechanisms in ALL of their models. Fatar is generally recognized as a world leader in these designs and many other prominent instrument manufacturers also use Fatar parts in their production models. For reference purposes, the particular model shown in the accompanying photos is NOT taken from a Nord, but is a generic Fatar part used for illustrative purposes only; most Nord models actually use somewhat more complex Fatar designs.
BASIC OPERATION
Photo #1 shows the general overall layout of a typical Fatar keybed. Depressing a key causes two small "points of contact" to press against the top of the associated "rubber key contact." Each such contact behaves something like an ordinary drain plunger, descending onto the PCB (printed circuit board); two small rubber nubs located on the underside of the key contact, one short and one long and each infused on it's end with a carbon derivative to make it conductive, then come in direct contact with associated contact points on the PCB, closing those circuits and letting the keyboard's computer brain (CPU) know that a note was just played. Because those two rubber nubs are of unequal length, they close the PCB circuits at slightly different times. The CPU calculates the time differential and uses this information to determine the midi velocity value of each note played.
Physically, each key pivots over a fulcrum point located very near the "head" of the key (furthest away from the player) where a retaining spring helps to hold the key in the top of it's travel position. At the other end, a "stop" limits the bottom of the key's travel position; this stop has a small rubber bearing surface which slips over the hard plastic of the actual frame. Less obvious, the stop also serves to limit the top of each key's travel position. Labeled "stop retainer" in Photo #1, there is a loop of plastic on the underside of each key which, when correctly positioned, encircles the stop. When abused, this plastic loop can break off with the result that the key's position at rest will be abnormally high. Also worth mentioning here as that the rubber bearing which fits over the stop can be accidentally rotated out of position (or come off completely), which will also result in abnormal key positioning and behavior. This bearing is VERY unlikely to rotate or come off even during the worst abuse, but can become dislodged from their normal position when the unit is open on the bench. In Photo #1, the first 8 such bearings, counting up the scale from the F# key, are in their normal position, after which they are all rotated 90 degrees out of position.
COMMON FAILURE MODES
Probably the two most common true keybed failure modes are: 1) dead key, and 2) full velocity key. Each case is generally attributable to a keybed's worst enemy: DIRT. The rubber key contact system does a really good job of sealing the PCB against infiltration of foreign matter the way it tucks down tightly against the PCB -- almost. As a design necessity, really small ventilation channels are built into the contact strips to give the air in the chamber underneath the rubber key contact a place to go when a key is depressed. This permits a pathway for dirt to inhibit the closing of the contacts; in fact, releasing a key will cause a slight vacuum in that chamber which will suck air back in as it returns to it's normal at rest state, and potentially carry dirt with it.
Any tiny piece of dirt on either the PCB contact points or the carbon-tipped rubber nibs can interrupt the normal operation of the key. If the "initial contact", as labeled in Photo #3, fails, the keyboard's CPU will read the "final contact" right away, assume that the key was played VERY hard, and cause a midi velocity of 127 to be played. You're playing a scale or a chord and one note sticks WAY out with full volume. Making things appear to be more complicated than they are, this will not happen on organs, only synths and pianos (and piano-related sounds such as clav). This occurs because the organs are not velocity sensitive by design (to conform with the original organs after which they are modeled).
If the "final contact" or both contacts are failing, the note will not sound at all. If the final contact, the CPU will get the first signal, but not the second, and never send the note (or if it does, it will send at a velocity equals zero state). Obviously, if both contacts fail, no note exists.
I receive emails from users experiencing these conditions who worry about using their Nords in such a state: "Will I damage my Nord by continuing to play it?" is a common question. The answer is NO, although you might damage your own ego and also perhaps other people's good opinion of your playing ability. For years I have thought that dust covers were simply a stupid excuse for shops to extract additional monies from customer's pockets, but shop experience has shown me that EVERYONE should both OWN and USE a dust cover on their instrument. When these types of failures occur during the warranty period they are handled as warranty repairs, but in point of fact these problems are NOT related to any sort of manufacturing defect, but from dirt infiltration caused by poor environmental conditions at the hands of the user (and his or her cookie-eating toddlers...?).
It can happen that total key failure will occur when both sets of contacts are functioning normally; this will generally be due to a cracked or bad diode (ok, I should have flipped the thing over and gotten a pic of the diodes on the other side). These diodes are very glassy in appearance and even close inspection under a microscope can sometimes fail to disclose a crack/fault in a diode, but a competent tech will know how to test, and if necessary, replace these. Such a repair as a diode replacement, btw, should be quick, easy and relatively inexpensive; those are NOT exotic parts requiring delivery on a slow boat from Sweden, but are readily available generically in the electronics marketplace worldwide.
"SQUEAKY KEY SYNDROME"
Some Nord owners have reported what I have come to call "squeaky key syndrome." In my first two months on this job I had NO reports of any such thing. Then suddenly I had a small "epidemic" of them, about 5 or 6 complaints in a 10-day period. That was two months ago, and I haven't had another such complaint yet. I have not yet personally heard a unit with "squeaky keys", and I have been using Fatar controllers for many years. However, I have a high degree of confidence that I know what this is and how to "fix" it. These "squeaks" are occurring at the point of articulation of the plastic end of the key against it's steel retaining spring (the only other possible location would be the fulcrum, which seems MUCH more unlikely). In these instances, it is likely that simply removing and reseating the offending spring will eliminate this somewhat trivial noise. Stubborn cases may require VERY CONSERVATIVE application of a SILICON-BASED, non-conductive lubricant in the area where the spring seats against the key. This is another situation where there is absolutely NO reason for undue concern; it is okay to play your instrument under these conditions -- doing so will NOT harm your Nord in any way.
