Toshiba 26hl47 lcd tv

[cadiman]

I picked up a Toshiba 26" lcd tv 26HL47.

It turns on fine, I have audio and can go through the inputs, and good backlight too.

It always shows a white screen even if I unplug the t-con.

The t-con is good and I have voltage to it.

The panel is a CHI MEI "China"

Anyone get any of these to work on yet?

I hope I don`t have a failed panel!

Thanks,

Cadiman

[Dgtech]

Re: Toshiba 26hl47 lcd tv

Post some pictures of what you're seeing. When posting pictures, use "Manage Attatchments" on the posting page.

[cadiman]

Re: Toshiba 26hl47 lcd tv

Thanks! I will need to do learn how to get good pictures with my sony. I will start posting pictures soon. I will say sorry in advance as I am sure I will screw something up on my first attempt.

Cadiman

[senndogg]

Re: Toshiba 26hl47 lcd tv

hello.
decided to continue this thread.
have a Schaub-lorenz 26" tv with Chi-Mei panel, white screen syndrome.
white screen with the lvds disconnected too.
the tv been has recapped lately as i can see.
there have been unsuccessful efforts for repairing it but no visible signs of swapped components, so i think this TV has only this fault.
stripped it.
SMD fuse ok. there is 5V and 3.3V all over the t-con.
but no 15-20V. i doubt the boost converter. i know in principle how a dc-dc converter works but can't tell here what should i measure. should i look for AC or DC current in this chip?
thanks in advance.

[senndogg]

Re: Toshiba 26hl47 lcd tv

here are so close photos.

[retiredcaps]

Re: Toshiba 26hl47 lcd tv

SMD fuse ok. there is 5V and 3.3V all over the t-con.
but no 15-20V. i doubt the boost converter. i know in principle how a dc-dc converter works but can't tell here what should i measure. should i look for AC or DC current in this chip?

What is the part number U11. You are typically measuring DC voltage.

[senndogg]

Re: Toshiba 26hl47 lcd tv

here it is. http://www.alldatasheet.com/datashee.../AAT1168B.html

[senndogg]

Re: Toshiba 26hl47 lcd tv

no shorted caps. measured attentively every single one. most pins at the main ic show 1.6V.

[retiredcaps]

Re: Toshiba 26hl47 lcd tv

here it is. http://www.alldatasheet.com/datashee.../AAT1168B.html

Measure the DC voltage of each pin (32 in all including the GND) and list the results.

Figure 1 on page 13 will help you understand the chip better and what the expected outputs should be if it is working. Pin 22 (VDD) is key.

[senndogg]

Re: Toshiba 26hl47 lcd tv

here there are retiredcaps.

[retiredcaps]

Re: Toshiba 26hl47 lcd tv

1) What is the part number for Q3 on the t-con?

2) Post a picture of the main/logic board as well.

[senndogg]

Re: Toshiba 26hl47 lcd tv

1) it says AC 4410N 257FC. no info in the entire web about it.
2) photos attached. but im sure the problem is in the first section given as there lack the right voltages.

[retiredcaps]

Re: Toshiba 26hl47 lcd tv

here there are retiredcaps.

Well obviously the readings aren't what they should be compared to the datasheet. So either that chip is bad or something is causing it to shutdown.

[retiredcaps]

Re: Toshiba 26hl47 lcd tv

but im sure the problem is in the first section given as there lack the right voltages.

It is quick and simple just to check the voltage regulators to make sure they are correct. It should take you less than 5 minutes to verify and that eliminates another possible problem.

[retiredcaps]

Re: Toshiba 26hl47 lcd tv

1) it says AC 4410N 257FC. no info in the entire web about it.

Someone needs to work on their search skills. The very first hit for "4410N datasheet"

http://www.alldatasheet.com/datashee...AF4410NSA.html

Refer to pinout. See if the mosfet is shorted between S-G, S-D, and G-D.

[senndogg]

Re: Toshiba 26hl47 lcd tv

oh god why.... i have misspelled it during the search. thats a my terrible fault

and G-D is shorted!!!!!!!

now i'll try desoldering it and im gonna let you know!

a great thank and a double rep+ in advance for retiredcaps.

[senndogg]

Re: Toshiba 26hl47 lcd tv

great news!

WE ALTOGETHER FOUND THE PROBLEM!
definitely the Q3, a SO-8 30V N channel mosfet, Anachip AF4410N.

i did not have a spare one, but instead i used the N sectionl of a dual channel AF4502, just for a try. it did work! now i am waiting for the AF4410N to be shipped.

thank you guys and specially retiredcaps for his patience, time and effort, and for correcting me

[retiredcaps]

Re: Toshiba 26hl47 lcd tv

WE ALTOGETHER FOUND THE PROBLEM!
definitely the Q3, a SO-8 30V N channel mosfet, Anachip AF4410N.

Over 2 years, I think this is a first. Normally, we see blown fuses, bad voltage regulators, and shorted ceramic capacitors on the t-con, but I believe this is the first bad mosfet found on a t-con/panel board.

[senndogg]

Re: Toshiba 26hl47 lcd tv

maybe the overall bad quality of the chi mei panel. the AF4502C worked for 10minutes, i suppose because it was somehow out of specs. will see if the 4410N will do the job or maybe another failed component overloads the boost circuit. i ordered 4 pieces.

[senndogg]

Re: Toshiba 26hl47 lcd tv

sorry for the long delay, internet upload problems; took nearly a month to repair.

so, the 4410N arrived, put it in there, and a nice 15V was found again in the panel board.
the voltage problem is declared FIXED!

but this cheap panel has suffered bad bonds also. after 1 hour the screen tends to whitish again, i firstly measured the voltages. the 15V was there, and when pressed the first tab bond the picture was ok. used some insulating tape for the job. tested the TV for 2 days and no more problems.


cheers!