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Key Contacts And Reliability


Chris Woollard

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Assuming an electromagnetic action organ is used in a large teaching room, heated during winter and smoking never permitted, what type of key contact is likely to be the most reliable over the years. Organ has a modern solid state switching system. Kimber Allen type silver or gold contact or the more modern Hall Effect type contactless switches. What are the advantages of each?

Many thanks

Chris

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Assuming an electromagnetic action organ is used in a large teaching room, heated during winter and smoking never permitted, what type of key contact is likely to be the most reliable over the years.  Organ has a modern solid state switching system.  Kimber Allen type silver or gold contact or the more modern Hall Effect type contactless switches.  What are the advantages of each?

Many thanks

Chris

 

======================

 

As an "end user" rather than an organ-builder, I've had experience of very long-lived gold-plated contacts.

 

On the other hand, as something of a mechanic, I am very dubious about the longevity of hall-effect anything. (Modern ignition systems use hall-effect sensors)In my experience, sensors can lose their magnetism and signal-amplifiers can go on the blink after a limited amount of time. I can't imagine that 122 new key-sensors, even for a two-manual organ, are going to be cheap to replace.

 

That stated, the conditions under which such components work in a modern auromobile, are a bit more extreme than inside an organ, as heat is the arch-enemy of magnets.

 

MM

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Having worked with both types of key contact system, here are some points to ponder...

 

KA type key contact assemblies are very reliable, provided that installation is very stable. Movement in the keyboards and contact rail is undesirable, otherwise the contacts and wipers can go out of adjustment (which at worst means a cypher).

 

Over a long period there is some loss of reliability due to oxidisation on the contact surfaces, and sometimes environmental factors (e.g. incense) can promote early problems. That said, it should be possible to clean a set of key contacts within the scope of a slightly extended tuning visit. The low switching currents that modern solid state systems employ leaves no arcing at the contact, which it seems to me IS desirable to a degree, in order to flash off dirt and dust.

 

Very often, a faulty key contact can be coaxed into life by vigorous repitition of the note, obviating the need for the tuner to visit.

 

The bottom line of mechanical key contacts is, that if you can see what's wrong you can fix it.

 

Hall-effect contact systems : again, require a very stable mounting or go out of adjustment. The system I have experience of employs a standard key scale (the distance from key to key). Not all keyboards are made to the same measurements, therefore retro-fitting H-E pre-formed boards is not quite as easy as it sounds.

 

The hardware & software that drives these systems will last for ...?

 

When it goes wrong and the tuner has to call, can he/she fix it then and there ?

 

Is a replacement circuit board/software needed ? How long will that take ?

 

How long will those parts be available ?

 

Bottom line : If you can't see what's wrong, can you still fix it ?

 

My money is with the tried and trusted mechanical key contacts. 99.9% of the time you can make a repair and leave, satisfied that all will be well and that even when you're dead and gone, the next technician can still fix the job!

 

H

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  • 4 weeks later...
Having worked with both types of key contact system, here are some points to ponder...

 

KA type key contact assemblies are very reliable,  provided that  installation is very stable.  Movement in the keyboards and contact rail is undesirable,  otherwise the contacts and wipers can go out of adjustment (which at worst means a cypher).

 

Over a long period there is some loss of reliability due to oxidisation on the contact surfaces,  and sometimes environmental factors (e.g. incense) can promote early problems.  That said,  it should be possible to clean a set of key contacts within the scope of a slightly extended tuning visit.  The low switching currents that modern solid state systems employ leaves no arcing at the contact,  which it seems to me IS desirable to a degree, in order to flash off dirt and dust.

 

Very often,  a faulty key contact can be coaxed into life by vigorous repitition of the note, obviating the need for the tuner to visit.

 

The bottom line of mechanical key contacts is, that  if you can see what's wrong you can fix it.

 

Hall-effect contact systems :  again, require a very stable mounting or go out of adjustment.  The system I have experience of employs a standard key scale (the distance from key to key).  Not all keyboards are made to the same measurements, therefore retro-fitting H-E pre-formed boards is not quite as easy as it sounds.

 

The hardware & software that drives these systems will last for ...?

 

When it goes wrong and the tuner has to call, can he/she fix it then and there ?

 

Is a replacement circuit board/software needed ?  How long will that take ?

 

How long will those parts be available ?

 

Bottom line :  If you can't see what's wrong, can you still fix it ? 

 

My money is with the tried and trusted mechanical key contacts.  99.9% of the time you can make a repair and leave, satisfied that all will be well and that even when you're dead and gone, the next technician can still fix the job!

 

H

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Having worked with both types of key contact system, here are some points to ponder...

 

KA type key contact assemblies are very reliable,  provided that  installation is very stable.  Movement in the keyboards and contact rail is undesirable,  otherwise the contacts and wipers can go out of adjustment (which at worst means a cypher).

 

Over a long period there is some loss of reliability due to oxidisation on the contact surfaces,  and sometimes environmental factors (e.g. incense) can promote early problems.  That said,  it should be possible to clean a set of key contacts within the scope of a slightly extended tuning visit.  The low switching currents that modern solid state systems employ leaves no arcing at the contact,  which it seems to me IS desirable to a degree, in order to flash off dirt and dust.

 

Very often,  a faulty key contact can be coaxed into life by vigorous repitition of the note, obviating the need for the tuner to visit.

 

The bottom line of mechanical key contacts is, that  if you can see what's wrong you can fix it.

 

Hall-effect contact systems :  again, require a very stable mounting or go out of adjustment.  The system I have experience of employs a standard key scale (the distance from key to key).  Not all keyboards are made to the same measurements, therefore retro-fitting H-E pre-formed boards is not quite as easy as it sounds.

 

The hardware & software that drives these systems will last for ...?

 

When it goes wrong and the tuner has to call, can he/she fix it then and there ?

 

Is a replacement circuit board/software needed ?  How long will that take ?

 

How long will those parts be available ?

 

Bottom line :  If you can't see what's wrong, can you still fix it ? 

 

My money is with the tried and trusted mechanical key contacts.  99.9% of the time you can make a repair and leave, satisfied that all will be well and that even when you're dead and gone, the next technician can still fix the job!

 

H

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Thanks for this, I decided on traditional mechanical KA switches the end and they seem perfect. As I built the solid state drivers also I used a new driver which enables varying voltage curve to be supplied depending on key speed - KA helped me do a minor mod. to their contact switch to enable this. Have had no problems with the mechanical nature of the contact and adjusting each independantly is very easy.

Chris

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