Sooner or later the battery will go dead on a TF1 module. It has a standard 3V CR2032 Lithium battery that can be found everywhere. When the voltage drops to low, the TF1 will fail to hold it’s memory and all patches and settings will disappear. Unlike the DX7, each TF1 doesn’t have a cartridge reader, but similar to the DX7 there’s no ROM memory. If you lose or edit the patches, the only way to get the factory patches back is to transfer them by sysex from a computer or another DX7. The TF1 lits the error led and displays a 4 if the battery voltage is too low.
As with a lot of synths from the early eighties, when patch memory was a novelty, the battery is soldered to the TF1’s circuit board. So it has to be desoldered to be changed. Then the new battery must be soldered back. One alternative is to put a CR2032 battery holder there instead, then next time no soldering will be required. I chose the battery holder path.
First you have to remove the TF1 module and it’s actually very easy to do. Unscrew two Philips screws on the back, and two screws with 2.5mm hex heads (IKEA style, but smaller) at the front. Then push the card from the back so it pops out of the front. Pull it gently towards you without using any force, it should go smooth.
I desoldered the old battery and used a solder sucker to remove the old solder. I then measured the distance between the two holes to approximately 16 mm.
Unfortunately I couldn’t find a holder with 16 mm distance between it’s pins, 19 mm was all I could find (bought here). Fortunately the pins were quite long, so I managed to bend them inwards enough for them to fit and penetrate the holes.I then soldered the battery holder and put the battery back.
A quite simple operation. I think it’s worth the extra time and cash ($2) with a battery holder. That time will be spared next time the battery must be changed.
I recommend this site for more info on the TX-816.