	AllExperts > Piano, Organ, and Keyboard
	Search

About Thomas Britanyak
Expertise
I am an organ/piano technician who has been actively involved with the design, building, repair, maintenance and installation of organs and pianos for 35 years. I began as a keyboard instrument apprentice and hold degrees in music and electronics. If you need a piano's date of manufacture, please go to http://www.pianoexchange.com/howold.htm or http://www.bluebookofpianos.com/pianoage.html I am happy to answer musical or technical questions, however, I CANNOT offer appraisals on pianos or organs. Please do not ask what an instrument is worth. For this service please contact an experienced local appraiser or try the following links: https://mmm1100.verio-web.com/blueb1/appraisal.html or http://www.57piano.com/questions.htm

You are here: Experts > Music/Performing Arts > Musical Instruments > Piano, Organ, and Keyboard > Yamaha digital kybrd keying

Piano, Organ, and Keyboard - Yamaha digital kybrd keying

Expert: Thomas Britanyak - 10/23/2009

Question
QUESTION: Hello,

I just got a used Yamaha PSR-170 that works fine except for one key (3rd C down from the top - of 61 keys), because the lower corner of that keying PCB got hit (somehow) and cracked off. It's the last key on that board (1 of 2 keying PCBs), and the only damage is that the interlaced trace fingers broke right in the middle.

How do these newer keys work? Is it some sort of capacitance trigger? But the fingers don't have copper under them, only the "hands" they're connected to do. I epoxied the piece back on and soldered a jumper wire to the broken hand, but it still doesn't work. Is there any way to repair it? If not, I'll just try and find another used one and keep this for parts, since they want $25-55 for a replacement board, which is pretty steep for just the board and a bunch of signal diodes! And a whole used unit sells for ~$50 on Ebay.

Thanks for any help you can give.

Dale McKenna

ANSWER: Hello Dale! Normally I'd say this is resistive keying as I recall. Based on your description...maybe not. In any case, the diodes you mention probably means the board uses a diode matrix to operate. Check the diodes with a diode tester and check the traces with a semi-conductor-safe continuity tester. It doesn't count if the traces look OK. Test them.

---------- FOLLOW-UP ----------

QUESTION: The diodes are fine, and aren’t anywhere close to where the physical break is. The copper traces only extend to the "hand" and the interlacing “fingers” are a non-conductive dark brown “paint”, but to my surprise, there is no copper under them. (??)

There are no electrical switches, and the only moving parts are the actual plastic keys and the rubber cones under each of them, which are the “spring returns” I imagine, but are not conductive. So I’m not really sure as to how this actually works. Does this make any sense to you, and/or are there any sites you know of where I might find more info on it? If I understood it, I might be able to come up with a solution. Any suggestions would be much appreciated.

Thanks again,

Dale McKenna

Answer
The plastic cones are used to give the keyboard a piano-like feel. When a key is depressed the cone provides a slight resistance to the travel and then suddenly gives way by inverting. In some designs, the keying "contact" is beneath this cone.

Check out http://mitatechs.org/ (Music Instrument Technician Association)

Ask a Question