|Original CR2025 battery
Back in 2008 a friend of mine passed me an FT757GX transceiver and an FC757 auto antenna tuner that he had got as part of an antenna and tower deal.
At that time the FT757GX suffered many issues, some of which it continues to suffer from today. The FC757 was also unwell with it unable to remember settings after being powered down. I suspected this was due to a discharged lithium battery inside. Lithium batteries generally have a shelf life of about seven years so, given the age of this unit, a flat battery would be no surprise.
|CR2025 and CR2430
|Battery mounting slots
Last week I opened the unit to see what type of battery was fitted. According to the manual it was a CR2025-D and this was confirmed on inspection.
I contacted my friend who runs a local photo shop, who supplied the battery for the FT757GX battery replacement, and asked if he could get me one. Unfortunately he couldn’t.
When I removed the battery it had a white powder around the edge indicating it had leaked.
I decided I would try to fit a CR2430 battery from Jaycar instead. I used one of these batteries in the TM742 battery replacement back in January 2011.
|Modified CR2430 battery
The CR2430 battery is about 5 mm larger than the CR2025 battery and the terminal spacing and width is also different.
|Battery tags before soldering
To make the CR2430 battery fit I bent the negative terminal from the edge to nearer the middle. I also cut the terminal to a vee shape so it would fit the slotted hole in the board. The positive terminal however didn’t fit as the two pins were too far apart. To overcome this problem I cut both pins off and soldered on a tag that I broke off the old battery.
This now meant the terminals aligned and it was easy to solder in.
Once the battery was replaced the FC757 remembered its settings when powered off.
|New CR2430 battery in place
Now I need to check the auto tune function.