Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

[budm]

Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

@budm thank you for providing that write-up for everyone. I'm beginning to see I have a main board issue most likely. Well at least it did.....until I came along!

Let's try to keep this simple....do you think I'll be able to get away with replacing diode D301 or do you think it's worse than that?

I already planned on replacing those mosfets, including the one I cooked. The board repair kit I found calls for IC U101, fets Q101, Q102 and Q502 to be replaced.

I'm thinking this kit is available for power supplies with shorted fets....and that's what I did......so I'm wondering with this info do you think these components have a good chance at resolving the damage I did? It would be cool if you could help me track it down, but I don't want this to become a pain in your

I'm going to place an electronics order soon and would like to see if I can get the power supply back up and running for further diagnosis?

1) Is diode D301 tested bad? Bad = Replace.
2) Are Q101, Q102 and Q502 tested bad? Bad = Replace. You can study on line to find out how to test them.
3) IC U101 no 100% test to verify if it is good or bad, so replace it.
4) The harder part will be trying to fix the main board which is really complicate so if the main board cannot be repaired by you then you may want to think if it is worth fixing the power supply board or not.
The whole thing a matter of willingness to spend lots of time to do the research and study or not to become good at anything.

[DXseekerMO]

Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

Last week I placed an electronics order including parts for this TV. They arrived. Tonight I replaced Q101, Q102 and D301, the components I damaged. I plugged in the TV, the fuse didn't blow and nothing went pop.

The TV would not turn on initially after installing the power supply

Here is an updated list of voltage readings in stand-by:

Main cap: 162.4-.5 steady

Connector P802:

PWM.........3.24v steady
5.1V..........NC
BL on/off.... 0v
Power TV....Varies 1.2v - 4v
A/C det.......Varies 0v - 3v
5.1V...........Varies 1.3 - 5v
GND...........ok
12V LNB..... N/C
GND...........ok
N/C............ N/C
12V AUD..... 0v
GND........... ok
N/C............ N/C
12V CC....... 0v
12V CC....... 12.7 holds, then varies

Connector P803:

L2- ............ 5.5-6v varies
L2+............ 55-65v varies
L1- ............ 1 -1.5v varies
L1+............ 50-62v varies

The remote control and power buttons were unresponsive.

I unplugged the TV for a bit to have a bite, and when I plugged it back in the green light around the power button illuminated, the screen lit up and the TV actually came on, but the screen was flashing so I re-checked the voltage readings and they were quite different:

Main cap: ...... 154V with backlights on, 160 without

Connector P802:

PWM.......... (point)1v steady
5.1V.......... NC
BL on/off.... 3.1v steady
Power TV.... 3.2v steady
A/C det....... 3.4v steady
5.1V........... 5v steady
GND...........ok
12V LNB..... N/C
GND...........ok
N/C............ N/C
12V AUD..... 10.9v steady
GND........... ok
N/C............ N/C
12V CC....... 10.9v steady
12V CC....... 10.9v steady

Connector P803:

L2- ............ 10.6v
L2+............ 74.8 - 75.4v varies
L1- ............ 7.3 - 7.9v varies
L1+............ 74.8 - 75.8v varies


Please remember that at one time I shorted the rectifier diode, pin EL105 to the heat sink as well as shorted the drain pin on Q102 to the heat sink and shorted pins EL203 and EL204 together at diode D301.

So there must be other damaged components on the power supply in the PFC circuit, or maybe I took out the rectifier (although it appeared to test good) I'm not too sure why the voltage was varying so much then as if by some miracle exerything kinda stabilized after unplugging and re-plugging the power cord.

The bottom line....I f'ed this board up a good one "testing" it, yet I installed some components....AND I SEE LIFE!

Truth told I never thought I'd see this TV work....

So would anyone have any insight or suggestions on what I need to check? I'm feeling pretty good just to get as far as I have!

[DXseekerMO]

Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

Interestingly enough, if I plug the TV in and wait for a bit the TV turns on and off just fine....and appears to have a good picture.....with main cap voltage about 162.

Along with last night's post, what am I missing here? Is the voltage at the main cap supposed to go up to 390 or not? I find it odd that everything works with such low main cap volts....unless that's how it's supposed to work?

[budm]

Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

There is not PFC Voltage booster on your PCBA version (you can see that the PFC parts are not installed on your PCBA).

[DXseekerMO]

Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

So this set runs at 160v at the main cap? Should I be concerned about the voltages at Connector P802, a couple of those are under spec?

[DXseekerMO]

Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

Ok so as of now the TV's actions are eerily reminiscent of this thread: https://www.badcaps.net/forum/showth...light=50l1350u.

I have my TV on a power strip with an on/off switch. I have to turn the strip off and on several times, wait 10 seconds and eventually the TV will turn on. Once I turn it off, I cannot get it to turn back on.

After reading that thread and with some research I learned these symptoms can be indicative of a corrupted EEPROM, main board location U2. I checked mine and found a suspect area on the top of the chip, pictured below.

Does anyone else think this EEPROM is suspect based on the symptoms I'm seeing and its appearance?

[diif]

Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

No, the main EEPROM is usually marked with a dab of paint. It would also be failed if it was the visibly damaged and whilst they control on/off functions it doesn't account for the low voltages.

[DXseekerMO]

Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

Interestingly enough....voltages are now where they are supposed to be and are steady.

This is something I don't have an explanation for, going from wild swings to absolutely solid and stable. Very weird

[DXseekerMO]

Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

EEPROM ordered today. We'll see if that fixes it.

[DXseekerMO]

Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

Well I'm pretty sure I cooked the new EEPROM. Going to order another one. I'm glad it was only $6.

[DXseekerMO]

Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

So the second EEPROM came in today. After installation the TV turns on and off reliably but the TV has no sound. If I do a channel scan, turn the TV off and back on again it will not remember the channels.

So does anyone have any ideas?

[DXseekerMO]

Fixed!

I replaced the main board and the TV has been working for 4 hours! It has a really good picture for an economy TV. Must be the LG panel......

Thanks everyone for all of your help, I appreciate it!

[DXseekerMO]

Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

Okay I had this TV sold about 2 weeks ago. I took it out to the shop, plugged it in and turned it on. The splash screen came up, the backlights dimmed then went out, resulting in sound with no picture. A picture was confirmed to be upon the LCD flap.

Fast forward to a couple days ago....I moved it in to the work area, turned it on and the backlights came on and stayed on....reliably. I had another TV come in so I moved it out and back in to the work area today. The splash screen came up, the backlights dimmed then went out with a picture on the flap. With all the movement of the TV and the intermittent nature of the problem I'm thinking a bad connection.

Today I cleaned the LED strip connector on the power supply and the connector itself, de-pinned the terminals from the harness side, squeezed the contacts to improve the connection to the pin on the PSU with no change.

I took the LCD flap out. After turning it on the LED's illuminated, dimmed then went out and stayed out. I was about to put the flap back in, but something told me to check them with the backlight tester. Sure enough I got to the third row and one of the LED's did not light. The rest did. The tester even showed less voltage consumption on that row.

I was a bit confused by this so I plugged the TV back in, turned it on and confirmed the LED that did not light with the tester did in fact light up when the TV was turned on, it dimmed and went out with all the rest of them.

I decided to replace the individual LED that did not light with the tester. After I tested the strip individually, and installed in the TV. It lit up fine both ways, even the tester showed more voltage consumption on that row. I turned on the TV....but the backlights still dimmed and went out completely.

So I cleaned the connector from the PSU to the backlights thoroughly, put it all back together (leaving the rear cover off), stood it up on the pedestal and turned it on, again splash, dim, backlights off. I wiggled all the connectors, tightened the screws on the boards and tried it again. This time the backlights stayed on. I have yet to turn it back off.

I think I'm dealing with a connection problem here, but the main reason I posted this is because I've never had an LED light with the TV and not light with the tester. I did have one the other way though. From now on when I'm troubleshooting backlights I'll be checking them all with the tester and the power from the TV.

The other reason I posted this is because this LED bead replacement was probably turned out better than all the ones before it...and I did it with a heat gun and not the ShopJimmy hotplate.

When the problem repeats I'll take some voltage readings and go from there.