Did two original batteryless mods: ADA MP-1 and Yamaha FX-500.

[Kazinator]

 

I posted about these mods to my mailing lists; the messages are archived here:

 

MP-1:

http://www.kylheku.com/lurker/message/20131031.165302.656d4689.en.html

 

FX-500: More complicated, custom PCB:

http://www.kylheku.com/lurker/message/20131110.004036.5ed1288c.en.html

 

What is this?

These vintage devices store their presets in an SRAM chip. SRAM vaporizes when the power is cut, so coin batteries are used to make the SRAM look nonvolatile (settings persist when device is off).  Going batteryless means replacing the chip with one that doesn't require battery backup.

Although the batteries can last a long time, there is the danger that you will suddenly lose your settings. In the case of the Yamaha, there is not even a way to back up your settings over MIDI: it has no MIDI OUT.

Neither the MP-1 nor Yamaha have any warning circuit for the battery going low. One day things will just fail.  You power up the unit, see some error messages and your presets aren't there, only factory ones.