Kenwood: Kenwood TH-28A Fault, need advice...

[rrpilot]

Need some advice, Kenwood TH-28A...worked fine an hour ago, now just displays this and won't respond to any keys....I know it's an older radio but I really like it, any ideas?

 

[AK9R]

Maybe dead memory battery. Maybe a bad or corroded connection inside the radio.

 

[MTS2000des]

Could also be a bad EEPROM itself. From the service manual, the backup battery only holds the operating parameters, such as VFO and "last used" data. Channel information is written to a serial EEPROM, (X24C04SI-3.5, 512 x8 bit EEPROM), which according to the manufacturer, has a life cycle of 100,000 writes. A radio of this age is probably approaching that limit, and once EEPROMs get errant, strange things start to happen. Assuming voltages are good, no leaky caps (likely as this radio made during the era of garbage time bomb SMD caps being common), it may be time to consider EOLing it.

 

[rrpilot]

Hey guys, thanks for the responses, I did the memory and VFO resets and that seemed to solve the problem, until I took the battery out for a few hours, seems that when I leave the battery in the radio it's fine, but if I store it overnight without the battery I get the problem.
Based on that on that what the manual says about how the memory battery charges I'm (Just guessing) the memory battery has reached the end of it's useful life.....any advice on replacing it?......I haven't done too much digging so I assume it's surface mount?.....I don't have much experience with surface mount components....

 

[MTS2000des]

It's not that difficult IF one has the right tools (a proper microtip soldering iron or hot air station), a good worklight/magnifier, and a steady hand.