Service manual

MODELS: LT-3280D/LT-3780D
Page 31
4.4.
4.4.
4.
Protection CircuitProtection Circuit
Protection CircuitProtection Circuit
Protection Circuit
LT-3280D and LT-3780D has two protection circuits and some fuses.
If the protection circuits work, The LCD turns to stand-by mode.
The protection operation can be confirmed by the blinking of the blue power LED.
And the content can be confirmed by the number of blinking within one cycle.
The following table shows the content of the operation.
Protection Circuit:
Fuses:
Name
Number
of blinks
Fault Location
Cause
Remark
POWER-SUB1 or
Panel
Excessive current
on the 120V line.
Only LT-3780D
POWER-SUB2 or
Panel
The 24V line on
the POWER-SUB2
is low.
Only LT-3280D
The voltage on any
of the following
output lines is low.
Check the fuses
on POWER board.
18V
(F9G2,F9G3,
F9G5~F9G8)
P5V
A
MPVCC
（
17V
）
4.5V
A
3.3V
D3.3V
A
D3.3V
D2.5V
A1.8V
POWER or MAIN or
Panel (Only 18V or
P5V)
Short1 1
Short2 2
Part No. Rated
Value
PCB Remark
F9A1 6.3A AC line
F9G2 500mA S8V line ,S8V line for S5V
F9G3 1A 24V line for S8V and S5V.
F9G4 500mA 24V line for S3.3V and D1.8V.
F9G5 1.6A 24V line for AMP VCC.
F9G6 4A 24V line for 18V.
F9G7 1A 24V line for P5V.
F9G8 500mA 24V line for 4.5V.
F910 1A POWER-SUB1 IC920 is broken.
POWER