I bought this toshiba as my 1st project. I am trying to teach myself electronics and have limited knowledge.
The error with this TV is that the power supply turns on, but a few seconds later turns off again with no picture and sound in between the times of clicking on and off.
The lights on the front of the tv change from the red standby to green and then back to red.
I have checked visually for bad caps and found 2 on the inverter which were bulging top and bottom, I have replaced these(2x35v 680uf). I then checked voltages (page 25 of pdf attached)
and found an incorrect voltage at 12v_lcd. Looking a bit deeper I found that 24v goes through an mp1591ds-lf-z step down converter (page 32 of pdf attached) to get this 12v_lcd
so I changed 2x35v 1000uf caps just after the 24v (schottky diode? page 30) and 2x35v 150uf caps on the 24v-12v step down circuit.
As this is my 1st project I'm unsure what voltages and responses to expect at the connectors on the power supply that aren't marked with a voltage, but I think POWER_LCD on the power supply might be an issue.
If I disconnect the cable from the power supply I have a voltage of approx 2.6v coming off the mainboard to POWER_LCD, but as soon as I connect it to the power supply this voltage drops to 0v
and when I turn the tv on this increases steadily to 1.4mV and then drops to 0v again a few seconds later when the power supply turns off.
While this is happening I also check the voltage at 12v_lcd. When I power the tv on the voltage at 12v_lcd changes to -1.5mV and then back to 0v when the power supply turns off.
So at this point I'm unsure where to go next. Could this be a fault on the step down circuit?
An help or guidance very much appreciated
The error with this TV is that the power supply turns on, but a few seconds later turns off again with no picture and sound in between the times of clicking on and off.
The lights on the front of the tv change from the red standby to green and then back to red.
I have checked visually for bad caps and found 2 on the inverter which were bulging top and bottom, I have replaced these(2x35v 680uf). I then checked voltages (page 25 of pdf attached)
and found an incorrect voltage at 12v_lcd. Looking a bit deeper I found that 24v goes through an mp1591ds-lf-z step down converter (page 32 of pdf attached) to get this 12v_lcd
so I changed 2x35v 1000uf caps just after the 24v (schottky diode? page 30) and 2x35v 150uf caps on the 24v-12v step down circuit.
As this is my 1st project I'm unsure what voltages and responses to expect at the connectors on the power supply that aren't marked with a voltage, but I think POWER_LCD on the power supply might be an issue.
If I disconnect the cable from the power supply I have a voltage of approx 2.6v coming off the mainboard to POWER_LCD, but as soon as I connect it to the power supply this voltage drops to 0v
and when I turn the tv on this increases steadily to 1.4mV and then drops to 0v again a few seconds later when the power supply turns off.
While this is happening I also check the voltage at 12v_lcd. When I power the tv on the voltage at 12v_lcd changes to -1.5mV and then back to 0v when the power supply turns off.
So at this point I'm unsure where to go next. Could this be a fault on the step down circuit?
An help or guidance very much appreciated
Attached Files