Toshiba 48L3451DB dead 17IPS20 Rev6 psu

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

Ok, so to update here, I have ordered another board, came up cheap on ebay so hoping its ok! Supposedly removed from tv with faulty backlights, so hoping its not a faulty driver cct on the board and the guy misdiagnosed it.
Will update in the next couple of days after its arrived and fitted.

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

Ok, so board arrived. Connected up to just the backlights expecting to see them glow up, but nothing!

So,thinking that the main needed to be connected I did just that, well what a surprise, still nothing. No standby light, no backlights, nothing!!! So what the heck?

The board was sold as working, tv stripped due to faulty backlights...
My question was "hi was it def the backlights gone or the circuit driving the backlights on the power board?
thanks"
His response was "Yes, was the back lights the TV powered on with sound and the display could be seen using a torch aimed at the screen".

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

I'm not blaming the seller here, just stating the circumstances. hope it doesn't sound like I am disbelieving anyone or making any kind of accusations.

Fully prepared to take it as a loss on the board.

[diif]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

Does a 42" Hitachi have the same backlights as your 48" Toshiba ?

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

probably not.

mine is 48" as you say, not had the leds exposed yet to see.
I have an led tester but theres 5 wires going into the panel and not sure how the led array is arranged. Which probes go where?

The replacement board was from a 42" so possible its not compatible but would think it would at least try lighting them up, could be wrong.

Both boards have the same led driver MP3394S.

It has also come to light that the power bd to main bd lead is connected differently.
From 12-20 pin connections as follows:
1st set is from the 42" hitachi 42HXT12U
2nd set is from my 48"
-11,12 to 7,8 same 11 to 7 & 12 to 8
-9,10 to11,12 same 9 to 11 & 10 to 12
-8,7 to 13,14 these are reversed 7 to 13 & 8 to 14
-6,5 to 15-16 these are reversed 5 to 15 & 6 to 16
-4,3 to 17,18 these are reversed 3 to 17 & 4 to 18
-2,1 to 19,20 these are reversed 1 to 19 & 2 to 20

so its poss I have buggered main and poss psu by connecting them up with these reversed.

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

So, this is new!
Peeled back the tape to discover the led connector broken off so looks like the panel needs to be disassembled to solder the socket back on for starters.

At a guess black - common gnd
blue,yellow, red & white - vcc

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

I think my concerns over the psu to main bd can be ignored as I am using the same cable and main bd.

Its probably a 98%, if not 100% chance the 2 17ips20 bd's have the same connections on CN4.

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

72 led edge lit panel

Black is (+)
blue, yellow, red & white are (-)

[diif]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

Yes, CN4 is the same. The 17IPS20 has been used in hundreds of different TVs, there's several versions of schematic and some changes with SMD resistors and capacitors.

The main differences will be around the MPS3394 controller. It will have been configured for the number of LED strings and a certain current and voltage to power them in order for it to be able to protect the circuit.
It's possible once you've repaired the wiring it could work but I'd think there will be more LEDs in your 48" than the 42", checking the placement and values of the SMD resistors around the MPS3394 will confirm this.

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

beginning to wonder now if its going to be worth it, obviously this has been stripped down before, signs of mistreatment, rounded off screw heads, broken plastic trims etc...

thanks, I'll try and get leds sorted first and go from there, perhaps revert back to the original power bd.

Meanwhile, what are the separating 'components' between the leds, light sensors?one has fallen off.

Each line drives 18 leds. 102v reading on led tester on all 4 banks. So 6v leds.

[diif]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

It's a rubber spacer to stop the big plastic panel crushing the LEDs.

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

doesnt feel like rubber and its soldered on

[diif]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

My mistake, hard plastic.

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

Sorry, I didn't mean to question/doubt you, just odd that its soldered on. The tab its soldered too does not appear to be connected to anything. And it is a single tab on closer inspection.

thank-you

[diif]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

Its a single pad that's not connected to anything it can't think of anything else it can be.
The other one looks flush to the PCB, are there any more ?

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

6 in total.
Yh your right, just plastic so not going to worry about them. Probably going to need another strip anyway.

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

So quick update, the original power bd is fine, connected it up to another main and it lights the backlight and drives the main bd fine.

So now just to find whats wrong with the main or get a replacement bd.

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

So just a quick note for ref:

Found that the 17IPS20 and 17IPS72 power bd's do not light up the backlights when disconnected from the main.

[R_J]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

So just a quick note for ref:

Found that the 17IPS20 and 17IPS72 power bd's do not light up the backlights when disconnected from the main.

This would be correct as they do not use pullup resistors on the control transistors like the Samsung power supply boards do

[notallbad]

Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

Update:
replacement backlights ordered, received and fitted

TV now working but bugger me theres now a thin blue line down the screen! wot a nightmare this tv has been.

Any helpful suggestions?

Its going to be another strip down and part out job I think.