Toshiba 40l1333b (SSL400_05DA) - backlight problem

[dfear]

I have a Toshiba 40l1333b with a backlight problem.

Problem:
The backlights don't light up.

Screen: Lta400hm23
LED Driver board: Ssl400 0d5a- Rev 1.0
Back light LED Strip connector board: SSL400_WP01 REV:0.0

Firstly I replaced the driver board, but that didn't fix the problem.

with the replacement driver board connected, I tested the led strips with an LED tester and all the leds light up.

I tested the leds using test points VOUT and IS (which are on the led driver board).

Also i have checked the continuity from the led driver board to the led strips, and continuity is OK.
I think there is a fault with the led driver board. I have attached two photos of the led driver board. The photo with just black test shows what the voltages should be at various points (i found these voltages from a photo I found on a forum). The second photo ( with the green text) show the results of testing the replacement driver board.

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Any clues which component on the led driver board in faulty?
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Update: I replaced the SN358 op-amp with with a LM358, but it made no difference.


Here is a number of photos with varying test results
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correct voltages on SSL400_05DA
http://testing.dfear.co.uk/toshiba_4...ack%20text.png

results of testing original SSL400_05DA (from the tv)
http://testing.dfear.co.uk/toshiba_4...%20results.png

results of testing replacement SSL400_05DA
http://testing.dfear.co.uk/toshiba_4...%20results.png

results of testing SN358, TR10E and CN001 - original SSL400_05DA
http://testing.dfear.co.uk/toshiba_4...%20results.png

results of testing SN358, TR10E and CN001 - replacement SSL400_05DA
http://testing.dfear.co.uk/toshiba_4...%20results.png

[budm]

Re: Toshiba 40l1333b (SSL400_05DA) - backlight problem

When you test the whole LED strip with the LED tester, what Voltage does it show on the tester?

[dfear]

Re: Toshiba 40l1333b (SSL400_05DA) - backlight problem

When you test the whole LED strip with the LED tester, what Voltage does it show on the tester?

I have tested all 5 of the rows of led strips (each row is a pair of strips). The positive probe of the tester was on positive testpoint on the first strip of the last row of leds and the negative probe was on the IS testpoint on the SSL400_05DA. The voltage on the tester was ~141 V. The test was done with the cable connected to CN001 on SSL400_05DA.

Individual rows are about 20-23 V per row. 2 rows have 2 strips of 4 leds and 3 rows have 1 strip of 5 and one strip of 4 leds.

[dfear]

Re: Toshiba 40l1333b (SSL400_05DA) - backlight problem

When you test the whole LED strip with the LED tester, what Voltage does it show on the tester?

The negative side of the connection between the two led strips on the last row seems to be dead at present, so that will need fixing.

Is it worth replacing all of the links between the led strips on all the rows with wire or rigid metal jumpers?

[zomi]

Re: Toshiba 40l1333b (SSL400_05DA) - backlight problem

Jumper the links

its a known issue on this model

[budm]

Re: Toshiba 40l1333b (SSL400_05DA) - backlight problem

Yep, bypass those surface mounted connectors on the strips with jumper wires.

[zomi]

Re: Toshiba 40l1333b (SSL400_05DA) - backlight problem

Once bypassed then retest
sometimes with the led tester all works fine but on the tv it doesnt
due to increases resistance on those points..

[dfear]

Re: Toshiba 40l1333b (SSL400_05DA) - backlight problem

Jumper the links

its a known issue on this model

I have fixed the backlight broken on this TV.

The problem was the crappy connectors that connect the led strip pairs together.

Solution:
I have soldered solid copper wire jumpers between the pairs of led strips. Only one connection was faulty but I put copper jumper wires between all of the led strip pairs, on both the positive and negative connections.

FYI:
The voltage on the LED tester (after the repair), when putting the probes on the IS and V_OUT test points on SSL400_05DA, was 124V.

FYI:
I used the solid copper wire from 1.0mm2 twin and earth electrical cable to make the jumper links.


https://obrazki.elektroda.pl/7825770300_1541702334.jpg