I have exactly the same problem, on UHF only (even though radio shows 8.4V after charging). Connected the FT-60's battery contacts (on the radio) to an external DC PS and it worked fine on UHF.
Bought a new original FNB-83 battery, charged it 10 hrs (8.6V after) and installed it last night, radio's been working fine since.
Hope this helps...
73, Ramon VE7RVS
