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In a recent shipment of parts, I got the memory battery trap door from an FT-980. On it was attached a 3-cell "AA" holder.

The OEM unit was a 2-cell (3v). Looking at the CPU Unit's RAM (uPD445LC) device specs, I see a max VCC of 7.0v. There are blocking diodes in series with both the 5v supply to the chip and from the battery bank to it, so the max applied voltage looks to be around 4.5v...and around 3.9v when the battery backup is supplying power. Well within safety limits.

Consensus on switching to a 3-cell arrangement? If will definitely give longer backup life.

73 - Fred, N8YX

I concur: 4.5V looks to be OK ... especially since the?

Note: the root cause of the relatively short battery life is extra leakage though R09 (>100uA). There is a simple mod in the Files section (?/g/Yaesu-FT-980/files/06%20-%20Mods/Article_%20Extend%20backup%20memory%20life%20to%2010%20years%20on%20FT-980.pdf?) that REALLY extends the life. Although I haven't tried the mod myself, the mod makes sense ... you basically add a transistor that will switch off the leakage path when the uC is "off".


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-Mat Breton, N8TW

My 40/75M FT-980 now has the 3-cell backup unit in place. That mod looks interesting, Matt. Next time any of them have to be disassembled to the point of CPU access (which I hope is never!) I'll perform the mod.

Part of my holiday ritual (both Christmas and 4th of July week) is to replace any AA backup batteries in the various gear that uses them with freshly-charged cells then throw the extracted ones on the charger for use elsewhere. Right now, two active FT-980s and an FV-102. An FV-101DM and several JRC NDH-51x memory units will be joining that collection, though I'm tempted to mod the JRC gear to use a 1F, 6v supercap in place of the batteries (which are a known major PITA in those units).

73 - Fred, N8YX

Hi Fred and Matt,?