Strong SRT8500 User manual

service manual
DTT1609

CONTENTS
3.2 COMPONENT LAYOUT OF MAIN BOARD
1.6 AUDIO
2.1 SCHEMATIC OF POWER SUPPLY
# ADDITIONAL TROUBLESOOTHING
3 SCHEMATIC.COMPONENT LAYOUT AND BOM OF MAIN BOARD
3.1 SCHEMATIC OF MAIN BOARD
3.3 BOM OF MAIN BOARD
1.1 SHORT TEST
1 MAIN BOARD TROUBLE SHOOTING GUIDE
1.2 POWER
1.3 MAIN CLOCK
1.4 CVBS
1.5 RGB
2.2 COMPONENT LAYOUT OF POWER SUPPLY
2 SCHEMATIC.COMPONENT LAYOUT AND BOM OF POWER SUPPLY

Main Board Trouble Shooting Guide
(DTT1609)
Here are the procedures you can refer to whenever terrestrial receivers do not
operate properly. You can check problems and repair the units on the basic level
according to the following procedures
Main Board
1
2
35
4
7
6
8
910

1. SHORT TEST
☞Before turning on AC power, check POSITIVE VOLTAGE and also check whether SHORT
between GROUND's and PIN SHORT for TUNER are detected or not.
2. Checking POWER.
☞ +12V(SCART),+5V(ANTENNA_POWER,IR,VIDEO BUFFER,HDMI,USB), +3.3V(TUNER, FLASH,
CPU),+2.5V(DEMOD),+1.5V(DDR3,CPU),+1.3V(CPU DEMOD)
1

1
+5V
+12V
+5V For HDMI
6
+3V3 For
Tuner

2
+3V3
For C
p
u
10
+3V3
+1V5
For C
p
u
+1V5 For
DDR3
3
+1V3 For
Cpu
2

10 +2V5 For
DEMOD
5
+1V3 For
DEMOD
+5V For
USB
8
+5V For Video
Buffer
+5V For Audio

3. Check MAIN CLOCK 24MHz and SYSTEM CLOCK (PLL) to operate normally after SYSTEM
operates.
☞For the first thing, check 24MHz from Y401 flows into [OSCI(PIN B18)] of MAIN
CPU
If the 24MHz is unstable, Check Y401 is damaged or not.
If you are firm belief of damage for the device, then replace the device.
☞ And then, check that 800MHz is being supplied to DDR3 with RESET
If the clock 800MHz on Pin-J7&K7 of U401 is not generated from inside of the
chip,Please check the soldering state of U401,U402 and U403
(MAIN CLOCK) 24MHz
(DDR3 CLOCK) 800MHz

DDR3 CLOCK 800Mhz
MAIN CLOCK

4. In case that MAIN CPU operates normally but there is no VIDEO display.
▶ In case of no OSD display.
☞ If OSD is not displayed, check first if VIDEO SIGNAL is detected from
[R419(CVBS),R416(R),R417(G),R418(B)] of MAIN CPU.
☞ And then, check any part with no DATA after checking VIDEO SIGNAL from VIDEO
SIGNAL PORT of MAIN CPU, or SCART
▶ In case of no MPEG display
☞ There can be a variety of reasons for the case
☞ Check first that CHANNEL of TP SIGNAL is locked properly.
☞ After this signal input to the resistor connected to MAIN CPU is done normally,
A/V DATA comes out from MAIN CPU and flows into MPEG CHIP(MAIN CPU). If there is no
problem to here, it is thought that MAIN CPU and channel are operating without any
fault.
☞ In case of no MPEG display to this point, inspect any disorder by checking
U701(TUNER IC) and I/F of MAIN CPU.

VIDEO SIGNAL
If wave-form is not like this
picture, check that wave-form
output is normal from each
terminal

7. In case of normal VIDEO SIGNAL flowing out but abnormal AUDIO SIGNAL.
☞ Check that ADAC_L(U201 PIN2),ADAC_R(U201 PIN9) signals have normal inputting and
outputting from MAIN CPU. The signal is linked to SCART.
5. In case of no MPEG and no OSD at the same time.
☞ Check that 1Vp_p(0.7Vp_p for RGB) comes out normally from VIDEO PART(CVBS) of
MAIN CPU.
BLUEGREEN
RED CVBS

# ADDITIONAL TROUBLESOOTHING
1) STAND-BY mode on Set.
Ordinarily, STAND-BY mode results from SHORT on LNB. Check first if TR on LNB has
stopped, and then in case that STAND-BY mode resulted from wrong software, down-load
a proper software.
There is a TR's as a switching
role on the LNB bundle. 5V comes
out normally from Q751. If
voltage is not enough or steady,
check if the voltage is impressed
properly from Q751.
POWER SWITCH

2) Screen problem in color
If you have Black-and-White screen. It mainly results from distorted 24MHz
frequency. In case of no screen display or different
color displayed, it also mainly results from the Y401 problem. Additionally, in case
that the screen display works but is with one color only, for example blue, green,
or red, it mainly results from software fault(possiblely detected only on RGB TV).
RGB Circuit
RED GREEN BLUE

Red signal input
Blue signal input
Green signal input

3) Weak TUNER signal
Check first that the voltage is impressed to LNB. If there is nothing wrong in LNB
Voltage, check if the voltage is impressed well into TUNER bundle and if data flow
out properly. If every condition is satisfied, TUNER itself can be considered to be
defective. In occasion, precise inspection should be done in case that there is
SHORT between pins(fault rarely made by a worker).

4) Screen ratio problem
If a strange ratio in 4:3 and 16:9 is detected, the voltage of TV scart pin number 8
is below 9V. In case of around 7V, screen will be shown with 16:9 ratio. In case of
over 10V, the ratio will be 4:3. If there is still a fault on screen after adjusting
screen ratio, it means the resistance of R595 on the circuit is not 1K. If the
voltage is normal but the voltage switch does not operate properly, it means that
Q593 TR is not operating normally. In addition, Q592 can affect the problem because
Q592 is a TV/sat transferring switch .
16:9= 6V
4:3=11.3V
16:9-High 3.3V
4:3-Low 0V

2 SCHEMATIC.COMPONENT LAYOUT AND BOM OF POWER SUPPLY
2.1 SCHEMATIC OF POWER SUPPLY