[Kenwood] TS-830 Low RF Power: Advice Please

[Les Zwiebel WB6ORZ]

    A TS-830S here has plenty of Drive, but won't really tune and puts out only 10 W carrier Max., all bands. NOS replacement finals are no help.
    A check of the HV shows only about 425V instead of 800V (around 1/2). So:
    Might the problem be:
     - diodes in 1/2 of a bridged rectifier?
     - a cap?
     - or (hopefully not) a winding on the Xfrmr? 
    Thanks in advance.
    (((((73)))))
    Les