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SX PX73 C,E,G# keys can only be played once

We own a sx px73 digital piano and all of the C,E, and G# keys can only be played once after being turned on. When they are pressed, the sound produced is loud and prolonged (like when the key is pressed continually) and then after that no sound is produc…

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SX PX73 C,E,G# keys can only be played once

Eunicethelion

Eunicethelion
Philippines

Total Posts: 3
Joined: July 18, 2018

We own a sx px73 digital piano and all of the C,E, and G# keys can only be played once after being turned on. When they are pressed, the sound produced is loud and prolonged (like when the key is pressed continually) and then after that no sound is produced. Does anyone know what the problem is and how we can fix it! Thank you in advance!

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Posted on July 19, 2018 at 11:21 AM
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3 Replies

davetutt

davetutt
United Kingdom

Total Posts: 166
Joined: January 12, 2015

Re: SX PX73 C,E,G# keys can only be played once

Your keyboard scanner seems to be faulty. The 73 has a dedicated ic that scans the keyboard contacts twice to determine the velocity of the key press and it uses a small memory chip as a buffer also on the same board. This is a basic chip that from what I remember is pre-programmed to do the scanning and nothing else. It doesn't have bi-directional communication with the main processor on the voice board so is not like later pianos that are rather more complex. If the communication to and from this chip including the reset and enable process (on the under side of the keys on the printed circuit board) is faulty then you may well get this effect. However, given the age of the keyboard I would suggest that you take the keys out by removing the 8 screws with big washers under the piano and once removed from the piano turn it over. You can then look for signs of spillage as shorts on the key bus lines can cause a similar array of faults.
For notes that sound at full volume it means that only one of the contacts under each key is being activated and that there may well be either damage due to moisture or worse, orange juice or alcohol that has damaged the printed circuit boards or the diode matrix and the way they talk to the gate array chip on the board. Without an inspection it is impossible to tell what is going on. Perhaps you can do this and let me know.

One thing you can try before touching any of the keys, press the demo button and let it play. If this is okay then it is unlikely that there is an issue with the main voice board.

Hope this gives you a starting point

Dave

Posted on July 19, 2018 at 5:38 PM

Eunicethelion

Eunicethelion
Philippines

Total Posts: 3
Joined: July 18, 2018

Re: SX PX73 C,E,G# keys can only be played once

Thanks for the response!

It looks clean right of the bat but we've cleaned the contact board anyways. The demo works fine. Every 4th key(C,E,G#) is still broken though and can only be pressed once (loud sound and long sustain)

Posted on July 27, 2018 at 12:17 PM

davetutt

davetutt
United Kingdom

Total Posts: 166
Joined: January 12, 2015

Re: SX PX73 C,E,G# keys can only be played once

I can only suggest that it needs the key frame stripped and checked. It could be that there has been past corrosion of the printed circuit board which has cut a track. All pianos have different effects when these parts start to go wrong. Some only do error messages on the display, others are all at full volume with no touch sensitivity so it is a matter of finding someone to strip the frame out and check for spillage and PCB damage or contact contamination. This is a time consuming task to say the least and not really to be undertaken lightly! A systematic approach is required here.

Dave

Posted on July 27, 2018 at 12:35 PM