Sounds like a good cleaning is in order,
these radios don't like to sit idle, they are born to run!
Most of us use Deoxit or your favorite contact cleaner,
just the smallest drop, avoid getting any of the wafer switches
wet, they will soak it all up and that causes problems.
Take your time and you should have the radio working just fine.
Check the 9 pin male connector on the rear of the radio,
often this connection needs cleaning and that sends the
9v to the VFO. If it is missing it may have a short bare jumper
at pins 8+9.
Check all the screws on the pc boards, these radios
all have common grounds and sometimes the screws are
a bit loose, back them off and then hand tight.
Manuals are here in pdf no costhttp://www.n6wk.com/kenwood/
Check the meter for the HV level when in
transmit, often the HV caps are at end of life.
Please join other TS-5xx and 8xx hybrid fanshttp://groups.yahoo.com/group/TS-520_820_530_830/
you can read all the messages while you wait for list approval.