Dx7 strange problem, help me!

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Jorge de Carvalho
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Dx7 strange problem, help me!

Post by Jorge de Carvalho » Wed May 22, 2019 10:24 pm

Hello, I need your help to find what's going on with my Dx7

I did a video:

This only happens with B and C keys on the lower octaves

Thank you!

Abrazo

Jorge

Rasputin
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Re: Dx7 strange problem, help me!

Post by Rasputin » Thu May 23, 2019 2:18 pm

Jorge de Carvalho wrote:
Wed May 22, 2019 10:24 pm
This only happens with B and C keys on the lower octaves
Fairly random guess? Bad diodes in the key matrix in that specific section which ordinarily would prevent "ghosting".

crafter57
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Re: Dx7 strange problem, help me!

Post by crafter57 » Sat May 25, 2019 8:37 pm

Double triggering notes are due to the rubber contacts, they need to be replaced. I am experiencing exactly the same issue on my Casio Privia at the moment. You'll have to pull off all the keys and pull the rubber contacts, you can try cleaning them with alcohol but they're likely worn. I'm doing my 88 key Privia, not a lot of fun.
good luck

Mooger5
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Re: Dx7 strange problem, help me!

Post by Mooger5 » Mon May 27, 2019 11:02 pm

The FS keyboards don´t use rubber contacts, but three stacked laminated springs per key instead. Their state is always being scanned by a microprocessor. When a key is off, the movable middle spring is in contact with the top one and when the key is pressed it pushes the middle spring down, making contact with the lower one. The time the mid contact takes from the upper spring to the lower determines the velocity. Sometimes the upper contacts get stuck inside the frame and the movable springs never make contact in the rest position, fooling the key assigner. Some other times is just dust and grime in the contacts, or corrosion in the connectors... Truth is, never seen a diode fail and if it was the case, it looks like every key in the respective octave would misbehave, but could be wrong here. It could also be a faulty IC1 or IC2. Lots of probable solutions. Even a full reset could also fix it. Pff...
Herrare umanum est.

Jorge de Carvalho
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Re: Dx7 strange problem, help me!

Post by Jorge de Carvalho » Thu May 30, 2019 10:14 pm

Guys,

A friend of mine found a bad diode, changed it and now is like new! :)

Thank you a lot for your help!!

Abrazo,

Jorge

crafter57
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Re: Dx7 strange problem, help me!

Post by crafter57 » Fri May 31, 2019 2:48 am

Kudos to Rasputin for thinking Diodes..!! Mine has rubber contact issues henceforth my thoughts.
But as Mooger5 stated many possibilities for the same symptoms. Good Job, Glad the synth is fixed!!

Mooger5
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Re: Dx7 strange problem, help me!

Post by Mooger5 » Fri May 31, 2019 11:55 am

Rasputin adds another score!
If the ghost note was b3 then it was thr diode d36 failed open that caused it right?
Any idea why? The op played only octaves and maj7 intervals though it would seem other notes in the same octave would also be affected. I cant think of a better explaination other than my previous highly technical argument that "it fools the microprocessor" :)
Herrare umanum est.

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