Philips BTM2310 Service Manual page 22

TROUBLE SHOOTING
Look into if with focus action
and laser output or not
YES
Disc is running or not
YES
CD Reading ok
E: NO USB
Check USB socket if with 5.2V
voltage or not
YES
Check 1st feet of U20（USB_SW)
if with low level or not
YES
Check DM,DP signal if normal
or not
YES
USB reading OK
Check R47，R48，U1，U2's
NO FOCUS,TRACK signal，Check
Q2 is with LD signal，
loader and main board 's
Check R29，U1，U2's SPINDLE
NO
signal and 6PIN soft flat
Check Q310，Q311，main
board and display board's
USB connecting wire.
YES
Check L301 if with 5.2V
NO
voltage or not
NO
Refer to A's maintenance
NO
Check U1
Check L15，L16，ZD1，
NO
ZD2,U1，U20 etc components
method