The key contacts are dirty. Each key has two contacts to implement VELOCITY sensing. When a certain one fails to contact, then the note is sounded at full volume. The contacts are conductive rubber pills pressed onto circuit traces. Clean only with 99% isoprophyl alcohol and Q tips very gently. It takes a LOT of dis-assembly and care to do this. It might be better to take this to a repair shop. There is a possibilty that a liquid was spilled into your keys as well. Cleaning is the answer.
Hi Fredy,
Thank you for your reply.
Does this happen only with one particular key combination? I mean,
the C note of 4th octave, only when played with B of the third gives this trouble. Else, this is fine. Are these contacts inter related? If that is the case, which is the contact to be cleaned? Obviously, I'll make both octave contacts cleaned up, but just to know, which might be the dirty contact? C or B
Thanks again,
Suneer.
The keyboard is scanned as a matrix. There are disconnect diodes which prevent paths when multiple notes are held in dfferent octaves. The contacts are in groups, both mechanically and electrically... Usually you will clean all while unit is open . You did not give a model number so I cannot check schematics... There IS a possibility that someone dropped metalic stuff in the key areas such as a staple or paper clip which is shorting between the conductors.
Sorry for not mentioning my model number. Mine is a Yamaha PSR 2100. Thank you, Suneer.
Here is link for your service manual;
http://elektrotanya.com/yamaha_psr-1100_...
Scroll down to "get manual" and click on it. IGNORE other downlload links. The PDF file is 13 Mb of data. The manual has everything you or a competent tech will need to access the unit.
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