Toshiba Regza 46xv645u won't turn on, blinking power led

[Paddy707]

My Toshiba Regza 46xv645u won't turn on. It was working fine then when I went to turn it on one day, it would not come on. The remote and the power button on the TV can turn on the power, but all that happens is the power indicator led on the front blinks 3 times, pause, blinks 3 times ... for a few repitions, then the light stays on. There is clicking from the power board. Then the TV shuts off and the led light goes out. No sound or backlights come on. Tried reset, draining static, unplugging for 24 hours but nothing changes. When led light is steady, no buttons on the remote or TV seem to do anything, but the power off buttons work on both. I'm not very familiar with electronics so need some help to figure this out, even to get to which board has the problem.

[Paddy707]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

PS: I checked the fuses and they are good. The TV has power and I could detect the 5v standby DC. None of the Caps look bad. I have a MM to work with.

[budm]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

Is this your power supply board?
Toshiba 75014973 (PE0702A, V28A000962A1) Power Supply Unit
http://www.shopjimmy.com/toshiba-750...upply-unit.htm
Check those 3 white low Ohms power resistors R851, 897, 898 to see if one of them has open circuit.

[Paddy707]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

I checked them and they all have low resistance, no open circuits

[Paddy707]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

Thanks for responding. That is the correct power board.

[Paddy707]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

"Check those 3 white low Ohms power resistors R851, 897, 898 to see if one of them has open circuit."
I checked them and and the resistance is R897 = 0.6 Ohm, R898 = 0.7 Ohm, R850 = 1.9 Ohm

[Paddy707]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

I rigged up some loads and tested the outputs from the power board
There are 6 states of the TV.
Before pushing the power button = before
Immediately after pushing the power button = After
9 seconds later (relay clicks on power board) = 9s
22 seconds after pushing the power button (relay clicks on power board) = 22s
25 seconds after pushing the power button (relay clicks on power board) = 25s
Power shuts off after 58 seconds

I attached a matrix of voltages observed from the different Power Board output cables (all cables still connected).

[budm]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

I am still looking for the SCH for the power supply board so we can locate some test points and see what signals/Voltages are missing.

[Paddy707]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

I also get 160V DC on the Bridge Rectifier. It goes before = 160V, After = 160V, 9sec = 160v, 22sec drops to 135v, 25sec back to 160v and stays there even when TV shuts itself down. I assume this is normal?

[budm]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

There are two section of the main power supply as you can see there are two 450VDC for one section, another one is 400VDC for the STBY section, those 450Vdc caps should kick up the Voltage close to 400VDC due to the PFC Voltage booster circuit when the TV is turned on.

[Paddy707]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

Hi Budm, thanks for helping me out here. I'm not experienced with electonics, so sorry for not understanding.
Are you asking me to measure the voltages on the board?
Are there specific points I need to take the voltage measurements?

[Paddy707]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

Managed to get the voltage reading from C820 and C821. They seem to be wired in parallel. The voltage is 162V with the power to the TV. Then, after pushing the Power button it is 162v, after 9 sec a relay clicks and the voltage jumps to 390V, then after 22 sec another relay clicks and the voltage starts dropping slowly back to 162V and then stays there.

[budm]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

So the PFC Voltage booster is working but some how it looks like the relay command on signal drops out so the Voltage goes back down to 160VDC.
You may want to leave the meter probe on the POW_SIG pin of the connector PJ91 with ref to the chassis GND to see what you have when the TV is OFF and when the power switch is activated and when the relay drops out.
The TV may have detect the fault some where so it goes back into standby mode.
You also need to check all the DCV of all those connectors to see what you have when TV is in standby and when TV is ON and when TV clicks OFF.

[Paddy707]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

Hi Budm, I captured as much of this info as possible in the attached table. It shows the voltages with power to the TV and before the Power Button is pressed, after the Power button is pressed, after 9 sec (relay clicks), after 22 sec (another click), after 25 sec (third click and led on Control board goes off, and finally after 58 sec when the TV shuts itself off and then stays in that condition unless unplugged.
For POW_SIG it stays at 0V until 9 sec point when it goes to 2.92V and then it drops back to 0V at 22 sec and stays there.

[Paddy707]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

Oops, meant to upload the picture version, here it is for easier viewing

[budm]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

Looking at the table, all the power supply outputs when the POW_SIG is present are OK, except the S_24V so that may be the clue as the circuit detects error so it shutdown the POW_SIG line.
So now we need to trace out the S_24V pin on the power supply board to see where it goes to next.

[budm]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

OK, I traced out the S_24V traces, that Voltage section is not used, the parts are not stuffed in that section: I.E. Fuse F897, L897, D897, C898, etc.
So it looks like some how the main POW_SIG and POW-LCD from main board drop out for some other reason.
The POW-TV command signal looks to be the one that controls the switched 18V-AUDIO and the switched 12V-W/load drops out way after the POW-SIG has dropped out.
This in not going to be easy without the diagram.
You can try removing the cable between the main board and the T-CON board to see what happen. At this point it looks like the problem is in the main board.

[Paddy707]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

I followed the traces on the Power Board for S_24V and it is actually not connected to anything. The trace has lots of locations for components, but none are mounted, so it seems to be an option that is not implemented on this board.

[Paddy707]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

BTW, I also checked the capacitors and the two fuses on the Inverter board and they all appear good.

[Paddy707]

Re: Toshiba Regza 46xv645u won't turn on, blinking power led

I did some more testing. There is a connector with 4 wires between the Main Board and the Inverter board. One of the wires (they are not designated) has 3.29V from when the power is plugged in which doesn't change. None of the other wires have any voltage at any time.
There is a two wire cable from the T-Con board to the Invertor board which has 1.6V from 9 sec after pushing the Power button until 22s and then it drops to 0V.