Toshiba 58L4300UC Dim picture

[Mayn]

I picked this up from a friend of mine. The problem was the picture was perfect, but the brightness would keep changing. They had someone come look at it and they changed the main board. didn't fix the problem, so my buddy just wanted it gone.
Now it just stays dim. Don't need a flashlight to see it or anything, it's just like you have the brightness turned all the way down.
The picture is perfect, just dim. No dark spots or anything. Menu, all inputs, nothing makes a difference.

I've measured all voltages going to the LED strips, and get 114V, so they seem fine.
From looking around these forums, the only thing that seems off is the PWM from the psu to the mainboard. I'm only reading 0.4V, and I think it should be around 2.5? There is no DIM labelled on the connectors.

Any suggestions? If that is the problem, is there anywhere I can 'steal' power from to make it work?

[budm]

Re: Toshiba 58L4300UC Dim picture

Pictures are too blurr for me to read the pins' label of the connectors.
BTW, backlights level adj. is not the same as Brightness level adj.

https://www.badcaps.net/forum/showth...943#post708943

If you know which pin is the PWM dim then remove that which goes back to the main board to see if the backlights will come on bright.
BTW, does it also have Analog dimming control pin?

[Mayn]

Re: Toshiba 58L4300UC Dim picture

Here are pics of the connectors on the power supply board.

If I remove the PWM wire, the backlights don't come on at all. I do still have a picture with the flashlight test though.

No idea about the analog dimming.

[budm]

Re: Toshiba 58L4300UC Dim picture

So with the PWM1 wire removed, what Voltage do you now on that pin of the power supply connector (need to know if it has pull-up resistor or not)? If it is <1VDC, then you can use 1K between the PWM pin and the stby 5V1 to see if the backlights will come on bright.

[Mayn]

Re: Toshiba 58L4300UC Dim picture

I get 0V at the power supply with the wire removed, and no backlights.
Trying to find a resistor to try connecting it to the 5v.

[budm]

Re: Toshiba 58L4300UC Dim picture

1~3K will be fine.

[Mayn]

Re: Toshiba 58L4300UC Dim picture

I just realized there is an ACD wire, which I believe is the analog dimming.
Also, 3k resistor to 5V1-no backlights

[budm]

Re: Toshiba 58L4300UC Dim picture

ACD = AC Detect, it is used to tell the main board if the incoming AC is within the operating range of the TV or not.
So with resistor in place, what dcv do you get now at the PWM pin?

[Mayn]

Re: Toshiba 58L4300UC Dim picture

PWM now measures 3.3V. image is noticeably brighter, but still not enough. I'm guessing it's about 50%of what it should be, even with the Backlights and Brightness set to max in the menu.
What's the max safe voltage to apply to PWM?

[Diah]

Re: Toshiba 58L4300UC Dim picture

could you post photo of the screen picture how dim its and backlight effect from the back of the tv.

we have here 2 measurements to know. 1 lum of th backlight. 2 the real LCD light contrast which T-CON play effect of it. also the main boards

[budm]

Re: Toshiba 58L4300UC Dim picture

PWM now measures 3.3V. image is noticeably brighter, but still not enough. I'm guessing it's about 50%of what it should be, even with the Backlights and Brightness set to max in the menu.
What's the max safe voltage to apply to PWM?

What is the LCD panel model number? We need to look for the spec sheet of the panel to get more info.
The PWM is usually between 10% (min backlights level) to 90% (max backlights level).
50% pulse width of 5V = 2.5V.
So at 3.3V I expect it to be quite bright.

[Mayn]

Re: Toshiba 58L4300UC Dim picture

Panel is a Chimei Innolux V580HK1-LD6 Rev C1.

The tv would be fine in a dark room, but unfortunately my living room isn't that dark.
If i could get it just a little brighter it would be fine.

[Mayn]

Re: Toshiba 58L4300UC Dim picture

One other thing. Before putting in the resistor and jumping the 2 wires together I had no ability to increase the brightness. After doing this, I can make it brighter. just not quite enough though.

[budm]

Re: Toshiba 58L4300UC Dim picture

The resistor is for the backlights level which is not the same as Brightness adj.. Right now the Backlights level adjustment in the on screen user menu will not have any effect because we remove the control PWM wire from the main board, you will see the on screen Backlights level indicator change but you will not see the effect.
The image on the screen looks normal, right?

[budm]

Re: Toshiba 58L4300UC Dim picture

Can I get the numbers as printed on the barcode sticker on the power supply board?

[Mayn]

Re: Toshiba 58L4300UC Dim picture

The image is perfect, just dimmer than it should be.

[Mayn]

Re: Toshiba 58L4300UC Dim picture

Power supply board # 01-PK101W0220I-VSPIM-E29-0541-100

[budm]

Re: Toshiba 58L4300UC Dim picture

OK, I found the board at SJ.
Toshiba PK101W0220I Power Supply / LED Board
http://www.shopjimmy.com/toshiba-pk1...led-board.htm#
I cannot find the spec. sheet of the LCD panel yet.

[Mayn]

Re: Toshiba 58L4300UC Dim picture

Any idea what feeds the PWM power? I might get bored this weekend and see if it's something I can repair myself.

[budm]

Re: Toshiba 58L4300UC Dim picture

Can I get the DCV reading of the LED connector pin:
LB1+
LB2+
LB3+
LB4+
LB5+

LB1-
LB2-
LB3-
LB4-
LB5-

There are 5 strings of LED in that panel and each one is controlled individually.