it does that.
I have a 6050 i removed knobs, front panel with glass for to do a thurough cleaning of the brown nico stain all over .
came out clean as new. glass has all the lettring for tuner stns. numbers., so just use mild sope and water.
cleaned and lubed all switches and pots for smooth noise free operation.
Then set AC and DC adjustments to spec and gave it a bench run with scope, function gen. and dummy loads
across the audio spetrum to see how it looked. All was well including 100hzzz, 1khz and 10khz sq. wave responce.
all were spot on.