Full Screen Display Or No Display On Vfd; No Operation Or Some Keys On The Front Board, Disordered Display On Vfd; No Sensitive Remote Reception, Or No Reception From The Remote Handset; The Machine Can Not Be Turned On Or Off - TCL DVD-F70 Service Manual

7. Full screen display or no display on VFD

a). Full screen display on VFD is often caused by abnormal -24V bias voltage. Check whether D5, C19 and R17
are disconnected.
b). If there is no display on VFD, firstly, check whether the filament lights in red. If not, and there is no 3.3V
voltage difference between AC1 and AC2, check whether D6, C9 and R21 are damaged. If the filament is not
red, while 3.3V voltage difference exists between AC1 and AC2, replace VFD.
c). If -24V and AC1-AC2 voltage are normal, check whether there are CS, DATA and CLK signals from CN301
on the front board. Then replace PT16312 (PT6554) under the condition that both of the above mentioned are
normal.
8. No operation of some keys on the front board, disordered display on VFD
Check whether the welding from the 12th, 13th, 15th pins of U301 to the 37th pin is in good conditions.
Check whether D301~D303 on the front board are damaged, whether circuit is disconnected, and whether R309,
R310 and R311 are open.

9. No sensitive remote reception, or no reception from the remote handset

Check whether the power source of the remote sensor is proper.
Check whether the remote handset is in good operation mode.
Use an oscillator to observe whether there is output wave from the 1st pin IR of the sensor after each pressing
of keys on the remote handset. If the remote handset is good, while no output from the sensor, the sensor is
damaged.

10. The machine can not be turned on or off

If the machine can not be turned on or off after pressing the STANDBY key on the remote handset and the
POWER key on the front board, replace the main chip U3.
Note: The above information is only for reference. If there is any mistake, please feel free to point out.