DX9 Servicing 101

One of the realities of owning vintage electronic music equipment like a DX9 is that at some point, something is going to stop working.

However, there is some good news. Inside a DX9 there is a lot less to go wrong compared to an 80's analog polysynth. It's a digital synth with no complex signal paths, moving parts or voice cards to fail. For the most part, the DX9 mainboard consists of fairly standard 7400 series ICs and a handful of custom Yamaha chips - and that's it.

The second piece of good news is that the most common issues with a DX9 are usually easy to fix. That is not to say that there aren't DX9s out there with serious problems. But, given how few DX9s there are and the fact that most of them have seen limited use, the odds are generally in our favour when trying to repair a DX9.

Note: These guides are provided as is and you undertake any of these repairs entirely at your own risk. These instructions come with no guarantees or warranties and I take no responsibility for any damage to equipment or injuries caused by following these guides.

Battery Failure & Replacement

The single most common fault with a DX9

The single most common fault you will find with a DX9 is a dead internal battery. The DX9 internal battery is a CR2032 permanently soldered on to the mainboard which has an approximate 10 year lifespan. Once it fails, it can be the root cause of several issues and it is generally not worth trying to diagnose any DX9 problems prior to replacing the battery and then loading in a set of factory patches.

To check the internal battery on a DX9, press the Function button and then hit button 19 until the battery voltage is displayed. If the displayed value is not between 2.2 and 3.3 volts, there is a problem with the battery. Readings of 4 volts or more have been the subject of emails to me and also debate on forums where individuals have suggested failed diodes and overcharged batteries which are liable to explode. In my experience, neither is more likely than the battery simply being dead.

This a DX9 battery test with the internal battery removed - as you can see, it gives an out of range reading of 4.5 Volts

For the DX9 - you could purchase CR2032s with attached legs or a CR2032 holder, but I do neither

CR2032s are an inexpensive 3V button battery that can be purchased pretty much anywhere

You'll need to open up your DX9 to replace the battery, which is pretty straight forward. There are 5 screws to remove, 4 on the top panel.

The remaining screw is on the back. Unplug your DX9, take out the 5 screws and the top panel can be opened on its hinges by simply lifting it up

The DX9 internal battery is a CR2032 that is soldered directly onto the main board. If you are going to replace it with a holder or legged battery - you will need to remove this board from the case. I don't, and do something a lot simpler instead.

With wire snips I cut the battery's legs, leaving enough of the positive leg (one nearest the keyboard) to solder a wire onto. Then I attach another wire to any ground point, i.e. the screw on the bottom right

With some insulation tape, attached the ground wire to the negative side / bottom of the battery

Take the positive wire and some tape and then attach that to the + side / top of the battery

Wrap some additional insulation tape around the battery to secure and fully insulate the battery.

Finally, tape the wrapped battery to the board. This doesn't look pretty, but works, is very quick and simple to do and means the next time you need to change the battery you can do it in minutes

Once that's done, close the hinged top, plug the DX9 back in and try the battery test again. Finally - load up a set of patches into your DX9 and you're done.