Problems in charging + electrical noise

I recently acquired PowerBook G4 laptop, seller said that it works OK otherwise but battery is dead. I bought it and quickly tested that indeed it works fine but battery won't charge.

Later I discovered that there is faint electrical noise coming from the machine when charger is connected, not from the charger but from the machine. I also noticed that Coconut Battery and Apple's own system info both display that the battery should have some capacity left, charge cycles are 159. However, sometimes the laptop shows maximum capacity to be something like 4000mah and then it may drop to 2800mah, also sometimes the machine claims zero charge cycles. Charge led sometimes changes from green to orange but only for a brief moment.

Also, I have three third party chargers which all have been tested to work in another machine but none of them work with this machine. No even that faint noise let alone charge/power up.

I have already tried resets and I did order new battery before discovering that something might be wrong.

So is it problem with battery, dc in board or motherboard?