Toshiba 50L 1400u No Power, No Standby, wont start

[Midwestside]

Found another (incomplete) thread about this tv, and perhaps the same problem. however it was not solved , so i figured i'd start a new thread about my unit.

I have included pics of the power board and the main board.
Fuse is oK. I checked voltages going from PWB to main board.
Leaving out of the PWB is a harness with 15 pins.
pin 1-3, 8 has 12v going out like it is supposed to.
pins 10,14 have 5v going out like it is supposed to.
The other side of the harness connected to the main board is receiving corresponding voltages that are being sent from pwb.

I ran a diode check on the PWB . (in circuit) D201 and D301/D302
had number readings in both directions . ie not OL.
Maybe that is something to consider.

If i remember correctly seems to be 40v going out of VLED 1,3,4
Standby light and remote sensor area seem to be getting 3.3v coming off the main board.

I do not have the remote at this moment. Physical power button does nothing, wont power on tv, wont kick in standby light. Have not taken main board off to look for cracked solder joints,, on the pwr button or otherwise.
I did cycle through a bunch of toshiba remote possibilities via universal remote phone app.

At first i thought power board, now im thinking main board.
I dont want to get a new main board and have the old power board fry the newly purchased main board. The TV was free to me. and 2 new used boards would run about 100.00, but i would like to try working small to big.
Perhaps someone could chime in here.

Sorry, i only have dropbox hosting.


PWR BOARD

https://www.dropbox.com/s/kbqkwciaoi...board.jpg?dl=0


MAIN BOARD
https://www.dropbox.com/s/8hm11ebz6vudnyd/main.jpg?dl=0

[attainteddragon]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

a full list of voltages in standby and after power was applied would be nice, and pin description.

pin 12 and 13. what are the value on these pins in both states?

[Midwestside]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

I cannot tell any noticeable differences between standby and pressing the power button reflected by the volt readings. Also no standby light to tell me 'its plugged in'

These are th readings as follows off the the 15 pin connector on the powerboard itself. I was encouraged to see touchine pin 13.. seemed to light the led board up and could see the light through the case holes, as i have the tv lying on its face. I couldn't get around to see anything was happening on the standby light or the screen itself.

I tested the voltages in the ways as follows.. pushing the power button
and taking a reading didnt seem to change anything. Besides, im not able to tell which mode the tv is in when plugging the cord straight to the TV.

A= power cord plugged in only B= power cord in me pressing power button
C= no cord plugged in


(as read on PWB side)

pin 15 a. 3.2v b. 3.2v c. 0v (DIM)
pin 14 a. 5.1v b. 5.1v c. 0v (5V1)
pin 13 a. 1.9v b. 1.9v c. 0v (BLON) Back light on? (however LED lit up when touched)

pin 12 a. 3.3 v b. 3.3v c. 0v (PWON) Power on?
pin 11 a. 3.5v b. 3.5v c. 0v (ACD)
pin 10 a. 5.1v b. 5.1v c. 0v (5V1)
pin 09 a. 0v b. 0v c. 0v (GND)
pin 08 a. 12.4v b. 12.5v c. 0v (12v2)
pin 07 a. 0v b. 0v c. 0v (GND)
pin 06 a.12.4v b. 12.4v c. 0v (12vA)
pin 05 a. 0v b. 0v c. 0v (GND)
pin 04 a. 0v b, 0v c. 0v (GND)
pin 03 a. 12.4v b. 12.4v c. 0v (12v2)
pin 02 a. 12.4v b. 12.4v c. 0v (12v2)
pin 01 a. 12.4v b. 12.4v c. 0v (12v2)



VLED pins (supposed to be 55v?)

Vled2+ a. 40.9v b. 40.9v c.0v
Vled1+ a. 40.9v b. 40.9v c. 0v
Vled3+ a. 40.9v b. 40.9v c. 0v
Vled4+ a. 40.9v b. 40.9v c. 0

Vled4- a. 4.5 v b. 4.5v c 0v
Vled3- a. 4.5v b. 4.5v c. 0v
Vled2- a. 4.5v b. 4.5v c. 0v
Vled1- a. 4.5v b. 4.6v c. 0v


Questionable Diodes

I know diode basics. supposed to get a reading in one direction only (that i know of)


N= (normal) black lead on stripe side, red lead on non stripe side R= (reversed) red lead on strip side black lead on non stripe side

(diodes in question)

D301 N= .145 R= .296
D302 N =.145 R = .296
D201 N =.176 R= .896

ALL THE REST OF THE DIODES READ: N = (some number reading) R= (OL reading)

[budm]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

Only 40V feeding the LED is not right, it means the Voltage boost converter is not working, so that is the section you need to look at. 1.9V BL-ON is on the low side.
At the same time these Voltages below should toggle HIGH and LOW when power switch is activated and not activated.
"pin 13 a. 1.9v b. 1.9v c. 0v (BLON) Back light on? (however LED lit up when touched)

pin 12 a. 3.3 v b. 3.3v c. 0v (PWON) Power on?

BTW, "(however LED lit up when touched" which LEDs, the backlights?

[dskall]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

You have a connector that comes from keypad. One or two or those pins should change voltage when you push buttons. Are you getting change when you push buttons? BTW you can post pictures. Go advanced, manage attachments

[Midwestside]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

Only 40V feeding the LED is not right, it means the Voltage boost converter is not working, so that is the section you need to look at. 1.9V BL-ON is on the low side.
At the same time these Voltages below should toggle HIGH and LOW when power switch is activated and not activated.
"pin 13 a. 1.9v b. 1.9v c. 0v (BLON) Back light on? (however LED lit up when touched)

pin 12 a. 3.3 v b. 3.3v c. 0v (PWON) Power on?

BTW, "(however LED lit up when touched" which LEDs, the backlights?

Which piece is the voltage boost converter? is it the sheilded piece, middle of board with the 2 transistors underneath?

I think my lead is probably touching the 5v and the BLON accidentally.
"led lights up" Yes i mean the entire back light.

[Midwestside]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

You have a connector that comes from keypad. One or two or those pins should change voltage when you push buttons. Are you getting change when you push buttons? BTW you can post pictures. Go advanced, manage attachments

The actual power button measured like 3.3v when i pressed it. it went to 0,
but when i released, it went back to 3.3v (this is on the powerbutton itself on the main board)

I will try to upload pics here.

[Midwestside]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

Just joined. did not initially see pics could be hosted here.
Here are the two boards.

[budm]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

Which piece is the voltage boost converter? is it the sheilded piece, middle of board with the 2 transistors underneath?

I think my lead is probably touching the 5v and the BLON accidentally.
"led lights up" Yes i mean the entire back light.

If that is the case then the BL-ON of 1.9V is too low to activated the Backlights circuit to turn on the Booster circuits.

[dskall]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

Seems you are not getting signal to fully turn on power supply

[Midwestside]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

I dont mind just buying a power board, if its gonna be a goose chase.

consensus is the power board and not the main board, correct?

[dskall]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

I think you have main board problem but budm is expert

[Midwestside]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

I think you have main board problem but budm is expert

So basically the main board perhaps needs to tell the powerboard 'to do stuff and isn't"

I got to the point where my knowledge ends. thats why i posted before getting into buying boards.

[budm]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

Disconnect just the BL-ON wire going back to the main board then use 470~1000 Ohms resistor between 5.1V PIN and the BL-ON pin to see if the backlights will come on.
BTW, did you check the solder joint of that BL-ON pin of the connector to make it is good?

[Midwestside]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

Disconnect just the BL-ON wire going back to the main board then use 470~1000 Ohms resistor between 5.1V PIN and the BL-ON pin to see if the backlights will come on.
BTW, did you check the solder joint of that BL-ON pin of the connector to make it is good?

Yes indeed, Backlight comes on with 680k resistor installed, Blon pin/wire removed. No other functionality however.

Solder joints seem ok under large magnifier loop inspection. No solder bridges either

[attainteddragon]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

can you confirm that the bl/on pin does not change voltage at all when powering on the set.

[Midwestside]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

can you confirm that the bl/on pin does not change voltage at all when powering on the set.

Just to clarify. I power on my set by plugging the cord into the socket.
The physical power button seems to do nothing. The TV is just 'on' or 'off'
based on plugging or unplugging the cord. When i mean 'on' i mean i can take readings,, no functionality, no backlight ( ive removed the 680 ohm resistor budm got me to test that actually got the back light LED to come on. I have since put the BL-0n wire back in the harness as normal and removed the 680 ohm resistor being used as a jumper)


So obviously unplugged there is no voltage anywhere.


In my case the BL-ON wire is pin 13 on PWB and purple wire.
Purple wire tested and has strong continuity (solid steady beep) from one end to the other.

Just to try, i depressed the power button in these tests. it made no difference to the readins.

(readings from PWB)
when plugging in and taking initial reading of BL-0N 13 pin power board side It gets a .01v and then immediately drops to .00v

(reading from Main Board)
The same as the PWB. BL-ON pin gets a little jump up .01v but then immediately drops to .00v



Are we sort of looking in the direction that the main board isn't sending proper V to wake up the PWB?

[Midwestside]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

Just to clarify. I power on my set by plugging the cord into the socket.
The physical power button seems to do nothing. The TV is just 'on' or 'off'
based on plugging or unplugging the cord. When i mean 'on' i mean i can take readings,, no functionality, no backlight ( ive removed the 680 ohm resistor budm got me to test that actually got the back light LED to come on. I have since put the BL-0n wire back in the harness as normal and removed the 680 ohm resistor being used as a jumper)


So obviously unplugged there is no voltage anywhere.


In my case the BL-ON wire is pin 13 on PWB and purple wire.
Purple wire tested and has strong continuity (solid steady beep) from one end to the other.

Just to try, i depressed the power button in these tests. it made no difference to the readins.

(readings from PWB)
when plugging in and taking initial reading of BL-0N 13 pin power board side It gets a .01v and then immediately drops to .00v

(reading from Main Board)
The same as the PWB. BL-ON pin gets a little jump up .01v but then immediately drops to .00v



Are we sort of looking in the direction that the main board isn't sending proper V to wake up the PWB?

TLDR: Basically no voltage change on or off, in the way you mean.

[budm]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

Since you are able to force on the backlights after removing the bl-on wire and everything else still connected but you still do not see any images on the screen and no sound, then you have more than just faulty Bl-ON command signal, at this point you do have bad main board.

[Midwestside]

Re: Toshiba 50L 1400u No Power, No Standby, wont start

Since you are able to force on the backlights after removing the bl-on wire and everything else still connected but you still do not see any images on the screen and no sound, then you have more than just faulty Bl-ON command signal, at this point you do have bad main board.

Thanks BudM.
I was ready to shell out the money for either board, one at a time.
I just wanted to make sure someone could tell me which as im just sort of learning this stuff. (can troubleshoot vintage audio recievers pretty good)