Afterburner 483

Hey guys.. I got me a old afterburner 483 linear.. putting a 8 watt dead key into it ..meter shows it pushing out about 200 watt.. with modulation it show bout 220 watt.. seems to be working really nice for its age.. but it has a small whine.. when keyed up... anyone have a idea what the whine would be.. radio checks say it not real loud whine..but there..an I can hear it.. the is sound coming from the box.. but cant pin point it..
I have 14 gauge wire going to straight to battery box..good ground.. or is this just normal for a old 2 tube box??

 

Drive Requirement to Trigger Antenna Relay ,1Watt
Max Drive (unmodulated carrier and FM}. _, 15 Watts
(amplitude modulated carrier) 3.5 watts
(amplitude modulated peak) .. , .. 14 watts PEP

That is from the manual.. If I'm reading it right 15 watt is max.. maybe I am not reading it right?

 

Thank you.. got that takin care of and it was easy enough.. just turned the RF power knob down

Will have to goes inside an turn the lower power pot down also.. that way I can leave the upper alone when not running box