The first thing I would do is install an new 3.6 volt 1/2 aa Lithium PRAM battery.
You can get it here: https://www.amazon.com/Brand-LS14250-Lithium-Battery-1200mAh/dp/B00F9AEWVO/ref=asc_df_B00F9AEWVO/?tag=hyprod-20&linkCode=df0&hvadid=196254346466&hvpos=&hvnetw=g&hvrand=2786393254070178141&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9028543&hvtargid=pla-392605939909&psc=1