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No sound from 8 keys in mid C range

Loved my PC88 until 1 note became loud. Thinking this was a contact problem, I carefully cleaned them. I reinserted them in the correct order. Now I have 8 dead notes - starting at Middle C# up to G#. I then bought a new contact strip and replaced the middle C octave. Still no change. (Oddly, middle C and the last 3 notes of the octave - A, A#,and B do work) What would cause 8 notes within the octave to suddenly stop working? Would appreciate any help you can give me

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  • moonlightmadness
    moonlightmadness Apr 02, 2014

    Let me begin by saying I bought the instrument new, has never been opened or abused, and has sit in my studio ever since. I recently did a hard reset, followed by a diagnostic test that checked out 100%. I replaced the octave with a new pickup strip that did not solve the problem. The only thing I did wrong was to install a few of the original pickups backwards. After the correct installation why did all the other keys (80) come back to life, and not these 8? Could this have an effect on the damaged keys? I have been unable to find a schematic of the key setup to learn how it produces a note. One site mentioned a diode which acts as an off and on switch as I understand it. Could reversing pickup magnets cause a diode to switch polarity?

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If this is the kind of organ with the wire sticking out of the key that makes contact with the bus bar to create the note you will have to make sure that key is operating the same as adjacent keys. The busbars have to be clean and the contact wires have to be clean. Sometimes when cleaning the wires they will spring out of place and not make contact with the appropriate bus bars. Check that key against the rest and see what you find. Hope this helps.

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The key contacts which are conductive rubber are dirty.

You need to disassemble to access the silicone rubber domes with the conductive rubber "pills". Carefully clean these pills using a QTip and ONLY 99% isoprophyl alcohol. Also carefully clean the circuit board where these contact.

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Thisis hard to troubleshoot... The keyboard insynths are usually scanned as a matrix... If a disconnect diode has failed, then wrong notes can be triggered. There is USUALLY rows of the diodes on the circuit board where the keys hit. There are usually TWO contacts per key in order to sense key velocity. The lkey contacts are usually conductive rubber pills pressed against circuit traces under the keys. One sometimes needs to clean these contacts using 99% isoprophyl alcohol and Q tips.
I would do further testing of ALL combinations of notes played together to see if possibly any others show up as that could point to a particular failure.

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The key contact has gotten contaminated. They are a black conductive rubber pill pressed against circuit traces on a board bellow the keys. Remove that key and maybe others to get at the contacts in silicone strips. Clean ONLY with 99% isoprophyl alcohol and Q tips. Clean both the pills (two per note) and the circuit traces they touch. You have to release the spring at the back of each key to remove the key.

Posted on Feb 03, 2011

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key-b2-playing-loud-not-touch-wy0wtjmd43l3of51yru11dct-4-0.jpg

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