I just want to share the fix of my Sony KDL-46XBR4. It had an intermittent milky white image, typical of a bad chroma chip. The T-CON board model is 404652HHC8LV1.8 from Samsung.
The chroma chip on the T-CON board is an ISL24005. This is a programmable one (through an I2C interface), but it has 4 input references (VREFL_L, VREFL_H, VREFU_L and VREFU_H).
Thanks to the designers of this T-CON board, all the tests points for VGMA1-VGMA18 are on the BACK side of the board. I had to measure the VGMA voltages on the front side at the vias going to the surface mount connectors.
As expected, the VGMA voltages were off while the problem happened. I traced down the problem to the 4 input reference voltages. They were easily measured at the top of the 4 capacitors (CG4-CG7) just below the chroma chip (ICG1). The 4 reference voltages were produced by a series of resistors on the bottom side of the board. Here are the measured voltages through the series resistors :
GND
RG24 (390 ohm) : 0.19 volt good, 0.01 volt bad (measured at CG7)
RG51 (0 ohm)
RG23 (10k ohm) : 6.14 volt good, 15.18 volt bad (measured at CG6)
RG 49 (0 ohm)
RG22 (2.7k ohm) : 10.23 volt good, 15.24 volt bad (measured at CG5)
RG50 (0 ohm)
RG21 (10k ohm) : 15.12 volt good, 15.31 volt bad (measured at CG4)
RG20 (390 ohm)
16v input
It turned out that the 10k ohm resistor (marked 01C in EIA-96 notation) at position RG23 was intermittently open. Later on I also found the 2.7k resistor at position RG22 with an intermittent problem. Replaced the two resistors and the TV set works like a new, with vivid colors.
The fix would also apply to the similar 404652FIX2HC6LV1.2 T-CON board also from Samsung, and to the following TV sets:
KDL-40WL135
KDL-40XBR4
KDL-40XBR5
XBR-46HX909
KDL-46W5000
KDL-46WL135
KDL-46XBR4
KDL-46XBR5
KDL-52XBR4
If you are aware of any other models not in my list please post them.
Thanks.
The chroma chip on the T-CON board is an ISL24005. This is a programmable one (through an I2C interface), but it has 4 input references (VREFL_L, VREFL_H, VREFU_L and VREFU_H).
Thanks to the designers of this T-CON board, all the tests points for VGMA1-VGMA18 are on the BACK side of the board. I had to measure the VGMA voltages on the front side at the vias going to the surface mount connectors.
As expected, the VGMA voltages were off while the problem happened. I traced down the problem to the 4 input reference voltages. They were easily measured at the top of the 4 capacitors (CG4-CG7) just below the chroma chip (ICG1). The 4 reference voltages were produced by a series of resistors on the bottom side of the board. Here are the measured voltages through the series resistors :
GND
RG24 (390 ohm) : 0.19 volt good, 0.01 volt bad (measured at CG7)
RG51 (0 ohm)
RG23 (10k ohm) : 6.14 volt good, 15.18 volt bad (measured at CG6)
RG 49 (0 ohm)
RG22 (2.7k ohm) : 10.23 volt good, 15.24 volt bad (measured at CG5)
RG50 (0 ohm)
RG21 (10k ohm) : 15.12 volt good, 15.31 volt bad (measured at CG4)
RG20 (390 ohm)
16v input
It turned out that the 10k ohm resistor (marked 01C in EIA-96 notation) at position RG23 was intermittently open. Later on I also found the 2.7k resistor at position RG22 with an intermittent problem. Replaced the two resistors and the TV set works like a new, with vivid colors.
The fix would also apply to the similar 404652FIX2HC6LV1.2 T-CON board also from Samsung, and to the following TV sets:
KDL-40WL135
KDL-40XBR4
KDL-40XBR5
XBR-46HX909
KDL-46W5000
KDL-46WL135
KDL-46XBR4
KDL-46XBR5
KDL-52XBR4
If you are aware of any other models not in my list please post them.
Thanks.
Comment