Grundig POWERMAX Q2, Service Manual

Page: 107 / 120

107
FAILURE/ERROR ANALYSES
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Sound available but no picture, and back-lights illuminated
In this section, we will basically explain where
we need to check if there is "no picture on TV"
even though there are not any problems in
the panel inverter. Here, we are assuming that
chassis is generally in good condition as we
obtain sound output from TV. When you cannot
determine if the back-light is working or not due
to the illumination level in the environment, you
are recommended to tap on the TV's front panel
lightly; if the back-light is working, you will no-
tice a slight glowing.
Before starting controls and repairs, it is cru-
cial to analyze and comprehend the problem
exactly. In this problem, you must make sure if
it is originated from the utilized source, if it is
a cable connection error or if utilized devices
have any problems or not.
Then, particularly LVDS cable on the chassis
should be checked for any disconnections,
loose parts, dislocations, breaks or ruptures.
Likewise, it will be proper to check cable con-
nections of the panel.
Later, the panel power (PANEL-PWR) supplied
to the panel T-CON board over LVDS cable
should be checked on T901 in the chassis. Panel
supply for the products with GF chassis is 12V.
If this supply is unavailable, whether 12V feed-
ing is present on S900 socket will be checked
from pin #4 or 5. If 12V supply is not found on
S900 socket although POWER_SW signal ex-
ists, PSU should be replaced. If POWER_SW
signal is not available, main IC and peripheral
components should be checked.
If VCC_PANEL voltage is found in T901 Leg 2
but not found in Leg 3; T1001 and peripheral
components will be checked. When TV is "ON",
a voltage around 3.8V occurs on Leg 1 of FET
as to be higher than 0V, and supply voltage on
Leg 2 is transferred to Leg 3. Check "TCON_
ON" signal, Leg 1 of R902 resistance. Here, if
the voltage is High, it means that panel supply
has not been turned on from the main integrated
circuit or software. This signal remains high
while the TV is going out of Stand-By and gets
down to 0V, 1 seconds before the picture ap-
pears on the screen.
If the panel is supplied voltage over LVDS, it is
most likely that picture information is transmitted
as well. Even if we do not have any precise con-
trol method for information flow over data lines,
the voltage is around 1.2V DC as detected by
means of a measuring tool. If this voltage cannot
be received, main processor might be faulty.
If LVDS data leaves Main Processor without
problems, problem might be in panel.
Besides, you can also consider problems includ-
ing that LVDS data is not being transmitted to the
panel properly, i.e. panel parameters are wrong
in NAND Flash or software installation error.
Problem can be eliminated by installing the ap-
propriate software.