Please don't try to tune the radio at this point,
some part has failed, leave it in receive mode for now,
otherwise you may have more problems trying to transmit
and you run the risk of damaging the final tubes or the
Please check the fuse and verify it is the correct amperage,
sometime they get replaced with larger value and that can
cause damage to the power transformer.
with the radio on in receive, move the meter knob to HV
and it should read about 3/4 scale, 900 volts or so.
if it is half or even less, you most likely lost the two HV
electrolytic capacitors. if you have good High Voltage,
then you may have lost one or more resistors.
Not sure of the history of the radio since it is new to you,
these radios don't like to sit idle, they get dirty switches,
and they really run well with a good cleaning.
Don't want to be a wise guy, there is dangerous high voltage
inside these radios so be careful and follow safety procedures
if you try to open the covers and run some diagnostics from
the manuals. Manuals here, service and operations, no cost in PDFhttp://www.n6wk.com/kenwood/
Please join other kenwood hybrid 5xx and 8xx fanshttps://groups.yahoo.com/neo/groups/TS-520_820_530_830/info
you can read all the messages while you get your membership approved,
the group is open to everyone, over 3,000 members worldwide.