Toshiba 37E200U No Power (Dead)

[zacheriaj]

Hello everyone. This is a customer TV and they said it stopped working after a storm. After all of the troubleshooting i've done, I figured it's time to come to the best Here are the output readings on the PS connector P802 while MAIN and Inverter disconnected:

Gnd: 0
24v AVD: 0
Gnd: 0
12v: 0
12v: 0
5v: 5.07
Pwr: 0
ACD: 5.07
Dim: 0
Inv: 0

Here is with inverter disconnected and MAIN connected:

Gnd: 0
24v AVD: 0
Gnd: 0
12v: 0
12v: 0
5v: 4.98-5.02 pulsing at about 1Hz
Pwr: 0.12-0.58 pulsing same
ACD: 0.08-0.15 pulsing same
Dim: 0.08
Inv: 0.01-0.04 pulsing same

I have tried to force on the PSU with a resistor and no change. Also used a 3v battery with no change. Tried to ground Pwr on and no change. pressing the on button remote and tv causes no reaction at all. I have checked diodes, optos, and transformers all seem ok but wouldn't hurt to double check if I get some other ideas. I assumed the main board was the issue but I don't want to replace it until I can verify if the power supply will work or not. Any help is much appreciated!

[budm]

Re: Toshiba 37E200U No Power (Dead)

When you try to force on the power supply, did you disconnect the cable going back to the main board first? you have to do that first.

[zacheriaj]

Re: Toshiba 37E200U No Power (Dead)

When you try to force on the power supply, did you disconnect the cable going back to the main board first? you have to do that first.

yes i did. also forgot to add, voltage across main filter cap is 163v.

[budm]

Re: Toshiba 37E200U No Power (Dead)

OK, you need to check the DC voltage on that SMD IC U101 for the 12V/24V SMPS power supply section, please see if you can read the P/N as printed on top so we can locate the VCC pin.
http://www.shopjimmy.com/toshiba-750...upply-unit.htm
If the power supply is damaged, you may also have damaged main board also since you are not seeing the steady PWR (ps_on) signal.
Is the power LED on the front of the TV ever come on?

[zacheriaj]

Re: Toshiba 37E200U No Power (Dead)

U101 appears to read 95195 5k163 313t. Very tough to read looks as if the print was wiped off.

[budm]

Re: Toshiba 37E200U No Power (Dead)

Please see my updated post 4.

[zacheriaj]

Re: Toshiba 37E200U No Power (Dead)

Power LED never comes on.

[budm]

Re: Toshiba 37E200U No Power (Dead)

I think you have more than one bad board at this point.

[zacheriaj]

Re: Toshiba 37E200U No Power (Dead)

That's what I'm thinking. Would it be cost effective to repair the power supply and attempt to diagnose the main?

[budm]

Re: Toshiba 37E200U No Power (Dead)

Fixing the power supply board may be possible, fixing the main board will be super hard especially without the diagram, we usually check the simple things on the main board such as the fuses and voltage regulators, and good visual inspection.

[zacheriaj]

Re: Toshiba 37E200U No Power (Dead)

Right and I have already checked those. Let's start with the power supply see if its a reasonable fix and if it is, I'll order a replacment main

[budm]

Re: Toshiba 37E200U No Power (Dead)

OK, it looks like pin 2 of U101 is the VCC pin, there is a filter cap C105 connected to it and primary ground, so check and see if you have >15VDC or so on THE TWO LEGS of C105, be careful no to touch anything with you body or hands since you are measuring voltages on the HOT DEADLY SIDE of the circuit.
SMD Q503 is the switched transistor (for supplying VCC to U101) that is turned on by Opto PC502, Opto PC502 is turned on by Q203 which is turned on by the PWR (PS_ON).
Have to thank Shopjimmy for providing good pictures of the board.

[zacheriaj]

Re: Toshiba 37E200U No Power (Dead)

Thanks budm, I will check that when I get home from work

[zacheriaj]

Re: Toshiba 37E200U No Power (Dead)

checked C105 without main board connected. no voltage at all.

[budm]

Re: Toshiba 37E200U No Power (Dead)

Check the DC Voltage on pin 1 and 2 of Opto PC502 when PWR pin is not activated and when it is activated.

[zacheriaj]

Re: Toshiba 37E200U No Power (Dead)

Correction.
not active:
Pin1-5.07
Pin2-5.07

Active:
Pin1-3.67
Pin2-3.25

[budm]

Re: Toshiba 37E200U No Power (Dead)

You have to measure right at the TWO pins of the Opto. One probe on each pin. When active, the voltage reading right at the two pins should about 1.6~1.8VDC.

[zacheriaj]

Re: Toshiba 37E200U No Power (Dead)

You have to measure right at the TWO pins of the Opto. One probe on each pin. When active, the voltage reading right at the two pins should about 1.6~1.8VDC.

1.11vdc

[budm]

Re: Toshiba 37E200U No Power (Dead)

OK, the LED is ON inside the Opto.
Please check the DC voltage on the Emitter of Q503 using the Primary Ground as shown in the picture.

[zacheriaj]

Re: Toshiba 37E200U No Power (Dead)

6.74 vdc