Read Sharp LC-20B4E (serv.man15) Service Manual online
16
LC-20B4E
TROUBLE SHOOTING TABLE
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Check all the settings microprocessor's adjust process menu.
Do F3301 and F3302
function?
Are T3701's secondary
outputs, +34V, +9V, +5V
and -11V normal?
Remove F3301 and F3302
and check the load side.
Is there short-circuiting?
Is there short-circuiting of
T3701 primary side periphery,
Q3703, Q3704 and S4701.
Replace F3301 and F3302.
Check S4701 and
connection cable.
Is T3701's primary oscillator
waveform normal?
Check T3701's secondary
load.
Yes
Yes
No
No
No
No
No
Yes
Check J3701 periphery and
connection cable.
Replace F6700~F6704.
Is the pin (120) of IC1201 in
the "H" state?
Is the output of Q3606 in the
"L
" state?
Yes
Yes
No
No
No
Yes
Yes
Check the OFL1 line, IC1201
and their peripheral parts.
Check the OFL line, Q3606
and their peripheral parts.
Check T6700~T6709,
Q6700~Q6714 and
connection cable.
Back light lamp failure to light up
Is the primary side of
T6700 ~T6709 periphery
short-circuiting?
Replace the back light lamp
with new one and check
again.
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