Sony CPD-G520P Service Manual page 18

c) Beam Current Protector Circuit Check
1) Connect constant current source to a section between
T901 (FBT) qa pin and GND, and check that the
RASTER disappers when the specified current flows
to the qa pin.
[Specification]: 2.12 + 0.00/– 0.01 mA
CPD-G520P (E) 2-2