Strange failure on Fatar Studio 900

[m_p_v_13]

I have a Fatar Studio 900.

7 of the black keys that are used for controller functions 1, 2, 3, 4, 5, and "inc", "dec" do not produce sound.* Those keys do have an effect when used in conjunction with the "program" control button to change the sound (produced by working keys).

All other keys, including the other black control keys, work fine.

Can anyone suggest some simple things I could look at to fix this problem?

Thanks very much for any guidance.

Michael Vogt

 

[m_p_v_13]

More info on the fatar studio 900 control black key problem

Those black keys that don't produce a sound actually do produce a very faint sound. I found this out when turning up the volume on the casio keyboard to which I connect.

Any ideas?

Thanks
Michael