Sanyo DP40142 No backlight

[Herbssat]

Hi gurus. I have this Sanyo set at the moment with no backlight at all. All the voltages have been checked at P802 and P803 and are within spec. 24v is going to the inverter and the voltage for bl on is 3.2v as well as the pwm voltage of 2.5v. The panel for this tv is the LTA400HM23. I could not find a detailed datasheet but i did see that the led driver for this panel is embedded. Maybe some of you guys can shed some light on this set. Your help is appreciated.

[kasfamily]

Re: Sanyo DP40142 No backlight

Show photo the led driver

[Herbssat]

Re: Sanyo DP40142 No backlight

Thanks for the response. Do not have a photo of the led driver. I looked at some of the specs of the panel on another site. P803 plugs directly into the back of the panel in the upper right corner.

[kasfamily]

Re: Sanyo DP40142 No backlight

Seen information that the led driver is inside the panel LTA400HM23

[Herbssat]

Re: Sanyo DP40142 No backlight

Hello Guys. Still looking for a response on this particular panel with the embedded led driver. Would only like to tear this set down as a last resort if possible. I can get some pictures up if needed. Thanks.

[Herbssat]

Re: Sanyo DP40142 No backlight

Screen is torn down to the led driver board. Jumped power supply with main board disconnected. Simulated Bl on signal with 3.3v battery supply. Still no boosted voltage at vout of led driver board. The driver board is a Ssl400 0d5a. I cannot find one anywhere. I did disconnect the led string while testing. The driver ic is a tr10e1. I cannot find a data sheet. All mosfets and boost diodes test good. Need ideas on this one.

[Herbssat]

Re: Sanyo DP40142 No backlight

I have narrowed the problem down to the led driver board. All 43 leds in the screen light up when tested. The forward voltage is 2.5v so i presume about 108v should be powering this array. Here is a picture of the board if anyone can help. 2 mosfets and 3 boost diodes. No datasheet at all on the pwm driver ic. Thanks.

[kasfamily]

Re: Sanyo DP40142 No backlight

http://www.kenotrontv.ru/forum/uploa...1407958929.jpg

[Herbssat]

Re: Sanyo DP40142 No backlight

Many thanks to you Kasfamily for your help. This gives me a good general idea as to what kind of voltage i should be seeing at the various points on the board. The only voltage i recall seeing is the 24v at both mosfets and the 3.2v or so near the connector on a smd capacitor or two. Why are parts so hard to find for this panel? The bottom line is i will have to rework the board just to get the backlights working again.

[kasfamily]

Re: Sanyo DP40142 No backlight

Must carefully check all the plugs on the led string, typically there is burnt contacts.

[Herbssat]

Re: Sanyo DP40142 No backlight

I will check for that but everything seems to be fine as far as the leds and strips are concerned. I did get a little aggressive and cracked one of the strips. I will have to see if i can run a jumper from one side of the strip to the other on both sides. I assume it does have copper like most boards.Reminds me of the old tv days. Does this led driver board have a shutdown circuit when it senses no load or should i be able to see the boosted voltage without the leds plugged in. As i mentioned before there is only 24v at vout. Thanks for your help.

[Herbssat]

Re: Sanyo DP40142 No backlight

Would like to expedite the process of repairing this set. I have 11.3v at the collector where 5v is shown. A transistor next to it checks bad in circuit. Also where is the 3v bl on signal going to on this board? A theory of operation would be helpful. Thanks.

[Herbssat]

Re: Sanyo DP40142 No backlight

Need help identifying a component. Looks like a transistor marked with W1 and the number 30 is under it. The board location is Q005. This is on the inverter board. Thanks.

[kasfamily]

Re: Sanyo DP40142 No backlight

Show foto

[Herbssat]

Re: Sanyo DP40142 No backlight

Hi Kasfamily. You already sent a picture of the led driver board with the voltages. What i can tell you is that both the base and emitter of Q00t4 and Q005 are tied together.Q004 is the transistor with the 5v.Q005 is also tied to pin 3 of the dual op amp that shows 16v.

[budm]

Re: Sanyo DP40142 No backlight

The photo from the other site is not clear enough to see the components and how they are connected together.
We need good closed up pictures of the both sides of the board and also in sections to be able to see the traces on the board.

[kasfamily]

Re: Sanyo DP40142 No backlight

Hi Herbssat. Need photo marking Q005. Here's what I found on this driver, it is not my

[Herbssat]

Re: Sanyo DP40142 No backlight

Thanks Kasfamily and Budm. Here are some pics. Hope these can help you to help me. Q005 is off the board. i presume it is a transistor also. It checks bad.

[kasfamily]

Re: Sanyo DP40142 No backlight

Picture quality is poor, but where are the photos Q005 ?

[kasfamily]

Re: Sanyo DP40142 No backlight

Q004 maybe 2SD1664 marking DA