in Synthesizers

DX7 II battery replacement


As you might know, all DX7 have a CR2032 battery, supplying the internal memory with energy. Depending on the use, the battery lasts for about 5 to 10 years and needs to be replaced afterwards. Once the battery is low, the DX7 isn’t able to hold the internal sounds, performances and settings in the memory. So, from time to time, a battery change is required. Here’s how to do it.

Check the battery

If your battery is low, this might look like (please note the rather scrambled patch name on the right side).

If you want to check your DX7’s battery status, you can do so by first pressing EDIT and then simultanously 16 and 32. This will enter the DX test mode.

On the left side of the display, the voltage is displayed. It’s missing the decimal point, meaning, 2v refers to 0.2 Volts. The expected voltage would be 32v, refering to the 3.2 Volts a CR2032 provides.

How to replace the battery

Turn the DX7 upside down and remove all visible screws on the underpart. Then pull the base in the direction of the keyboard and lift it.

Remove 5 screws from the CPU board and 4 from outside the backpanel.

Carefully unplug the cables to the floppy disk on the right side and those at the bottom of the cpu board.

Now you can lift and flip the CPU board slowly – please note: There still are cables attached, so take care.

Once the board is flipped around the battery appears:

Desolder the battery from the back side of the board.

Now, there are two reasons not to solder a 1:1 replacement battery directly to the pcb again, but instead solder some cables to it and place the battery somewhere else in the case:

  1. Next time the battery needs to be replaced, it would be beneficial not to need to solder again.
  2. In case the battery should leak, it won’t harm the pcb; don’t forget, batteries contain acid which can destroy pcbs.

I soldered two short isolated connectors to the pcb (using pins would have been the prefered solution but i didn’t had pins available, so …).

To these connectors i soldered the cables leading to the battery, manteld with shrinking tubes, to protect from unintended circuit shorts.

I fixed the new battery cables with cable binders to existing cables to ensure cable relieve.

To make future battery changes as easy as possible, I’m using a cell battery holder. I used the one from Sparkfun, called LilyPad Coint Cell Battery Holder.

My first thought was to use cable binder to fix the the battery holder on the right side of the case. This would have required to isolate the back of the battery holder, since there are plus and minus pole connectors on the backside which could lead to an electrical short if not isolated.

Instead i put the battery holder into an enclosure i found by coincidence. Like this it’s not only isolated but also protects the synthesizer from acid in case the battery should leak. There are cases specificly designed for this purpose, which would be the prefered solution. But as you know, i didn’t had one, so i used what ever seems to the job as well…

Don’t foget to add a CR2032 into the battery holder and move the switch to on.

Re-checking the battery voltage again:

Restore internal Sound Banks

After changing the battery, the internal memory is gone/corrupted. So you need to restore it.

The DX7 supports Midi SysEx which can be used to restore internal sound banks.

Before dumping the SysEx, a clean reset of the DX7 is recommended. A reset can be performed by first pressing EDIT and then simultanously 16 and 32.

Next step is to remove the write protection from the internal memory. Pressing pressing EDIT and then 14 leads to the following menu:

Per default the write protection for the INTernal memory is on. Set it to off using the arrow keys to navigation to the INT position.

To dump the SysEx you need to connect your DX7 to your computer via Midi. Get a SysEx program of your choice (i recommend SendSX for Windows users) and load the sound bank you would like to dump. The factory defaults for the internal storage you can download here.


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