Check the System Clock (27MHz)and the RESET terminal of CPU.
Check the UART communication terminals between CPU and digital board (UART0).
Check the I2C between CPU and LGDT3303 or EEPROM.
Check the Flash Memory or DDR-SDRAM.
Basic Inspection
Power Supply is O.K. but the DTT Does Not Wake Up
Preliminary Checkpoints
Useful Tips
1. An Unstable 27 MHz clock may be due to defect of X-TAL or clock generator (U261). Replace the X-Tal or U261.
2. DDR-SDRAM have difference clock inputs which are positive and others are negative signal (Double Data Rate).
3. Vref and VTT are have Vcc/2 and check the power source whether defected.
4. When replacing parts, be cearful of static charges from the tip of the solder iron that can easily damage the parts.
Also, check for assembly condition, soldering condition, or for incorrect or reverse insertion of parts.
5. If the problems are caused by CPU, change CPU board and download Serial Number.
Check the System
Clock 27MHz (Pin 15) of IC
MK2475-33G (U261)
Power Supply is O.K.
but the STB Does Not
Wake up
Check RESET, CS and OE
signals of Flash Memory
Check for other defective
modes
Waveform 5
Ch1:Reset, Ch2:CS/ Ch3:OE/
Check X-Tal(Y261) and
related parts
Check Flash Memory
(U40) or related parts
NG
OK
Check DDR-SDRAM Clock
(Pin 45 and 46) of DDR-SDRAM
(U5, U6, U7 and U8)
Check the Vref and VTT voltage
and clock of
DDR-SDRAM or related parts
NG
OK
Check system reset of Pin1 on
U281
Check the soldering state of
U281 or Replace U281
NG
OK
OK
NG
Waveform 2
Waveform 3
Ch:CLK, Ch2:CLK~
Waveform 4
Ch:3.3V, Ch2:Reset
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