Service manual

23
7-1. Dynamic Focus
Focus is poor
Is the
waveform of the
DF pin in FBT
correct?
PHILIPS : 440V 180V
NEC : 300V 120V
SAMSUNG : 300V 120V
1. Check the CRT socket
or connector wire
2. Trouble in FBT or CRT
1. Check the waveform of
the pin 3 of FBT.
2. Check D575
1. Check the 12V DC line.
2. Check Q751,D755
* Check after adjusting the static focus
finely by VR in FBT
DF
waveform
FVH
FVH FVV
FVV
No
Is the
base voltage of
the Q751 about
2.6V?
Yes
Yes
Yes
Is the
waveform of
the pin 10 in IC501
correct?
Yes
No
No
Trouble in Q752, Q753, Q754,
D751, D752, D753, D754,
Q755, Q756
Trouble in IC501 or C520
No
DF
waveform
4.5V
2V
0V
0.8V
Is the
cathode voltage
of the D575
about 600V?