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LG RD-JT40/41 Service Manual
33
6. DMD Board Trouble Shooting Guide
Check power voltages.
Check clocks from oscillator (58 MHz), from ASIC (58 MHz and 116 MHz), from FPGA (9.667
MHz and 2.4 MHz), to Hitachi (14 MHz), to motor controller (9.667 MHz)
Verify HSYNC, VSYNC, ACTDATA, SYNCVALID, POWERGOOD, RESETZ from computer or
source at 60 Hz. Verify these signals meet TI specified timing per Hardware ICD.
Verify color wheel index running at 120 Hz
If no color wheel spinning, check data transfer on the following lines: MTRDATA, MTRCLK,
MTRSELZ.
Verify phase lock of color wheel by checking rising edge of Index 275 us after Vsync
If previous steps are verified, microcontroller is OK.
Verify motor_spin line from microcontroller to FPGA is logic high.
Verify hardware LAMPEN to ballast. Lamp type must be set to appropriate type if problems with
getting LAMPLIT appear.
3.5 seconds after LAMPLIT, DMD should become active (unpark) and display an image.
Verify reset (HRESETZ, pin 1) from FPGA to microcontroller only goes low once during the lamp
strike period. LAMPLIT should be stable after microcontroller last reset.
If everything else verified, but still no image, perform the following checks:
Check DMD voltages at output of generation circuits, but also out of SR16 IC (be careful not to
probe on pins or the device could be damaged): VBIAS (22-25v), VRESET (-26V), VCC2 (7.5V).
Please attached file for reset waveform.
Check voltage enables from FPGA are active as appropriate. If not, output drivers may be
blown from previous probing.
Be sure two reset lines are not tied together or the device WILL be damaged.
Verify I2C communication by reading system status and microcontroller version. Verify READY
bit in Status Byte.
Set curtain mode to Full Green and verify green is displayed over entire screen. Repeat for Red
and Blue. This checks for functionality of TI electronics between ASIC and DMD.
If colors are wrong, check color wheel is spinning the correct direction. Put unit in red curtain
mode and use a photosensor to verify that red is displayed 220 uS after color wheel Index.
Use spoke light test register number 0x0E to verify sequence color transitions occur during wheel
spoke interval. See Software ICD for register 0x0E.
Other suggestions:
Be sure front end electronics are sending one pixel per clock.
Elastomer and DMD are aligned properly to pads.
Check data transfer on the following lines: PBCLKZ, PBDAT0, PBDAT1.
If Color wheel has difficulty in starting or is unstable, the timing capacitors may need to be
adjusted to match the motor parameter.