If you have a vintage Yamaha FM synth like the DX100, DX27 or DX27S and get the message “CNG RAM BATTERY!” This means the internal RAM battery is failing and if you don’t do anything it will lose your saves sounds when you power the device off.

My DX100 is getting on for 36 years old and needed battery change so I bought a battery and installed it in the synth.

I thought I document the process in case it could help anybody else out. In this guide and video, I show you how to change the internal battery on the DX100 which is also the same for a DX27 and DX27S (which are the same unit just with full size keys). Before you start make a backup of your user banks, I used DX Manager for Windows.

The battery is a standard CR2032 watch battery but soldered directly onto the board. So, you are going to need a new battery and a battery holder to put the battery in. I ordered the battery from Amazon along with this pack of battery holders. Using a battery holder means in the future you can swap the battery without any soldering requirements.

The first step is to remove the rear cover, making a note of the screw placement. Then you need to remove the screens from the circuit board as the battery is on the underside of the board. You can then desolder the battery and solder in the battery holder wires. I had some issues with one of the pins, the track had come away from the board, so I had to join it to the next solder point on the board which I admit doesn’t look pretty but it works. It was then just a case of putting the cover back on.

After the battery has been changed the internal programs had been lost. You can reset the DX100 by holding down buttons 1 and 2 while you power up the device and then saying NO to the test options. I tried this a few times, but it didn’t reset the user programs and of course they wouldn’t be my sounds anyway. This didn’t matter to me as I backed up my patches using DX Manger (see my video of the app) so I just transmitted the user banks back to the DX100 via MIDI from my PC.

My DX100 should be good for a few more years now despite my heavy-handed soldering! Here is my video guide to how to change the internal battery on a DX100.

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