Toshiba 32W3451DB Backlight Problem

[BBN]

I have a Toshiba 32W3451DL LED backlit TV - panel VES315WNDL-0 with no backlight - fails torch test but all signals etc OK. Actual LED strip(s) [??] not visible as within panel - not sure if PSU (which I assume includes LED driver) or actual LED's - how can I test/determine which and can anybody point me in the correct direction on to how to dismantle the panel gaining access to the LED's please?

[tom66]

Re: Toshiba 32W3451DB Backlight Problem

Have you checked if the power supply is giving the required output voltage for the LED strip (approx 40V?)
I say this because I fixed a similar set with a "VES315" panel (some crap Vestel junky LCD) and the fault was the PSU, shorted diode and FET on power supply dragging 24V down.

[BBN]

Re: Toshiba 32W3451DB Backlight Problem

If I knew what voltage to actually expect I would be measuring it.
At present - there are two connections to the LED(s) and a DVM across this pair indicates something odd - may be pulsed DC of some form.

Red wire LED to chassis approx. +27V DC. Black Wire LED to chassis/0V approx. 1.5/2.5V DC - but again suggests pulsed or something.

Can I drive the LED's with something else to test them? If so what?

[budm]

Re: Toshiba 32W3451DB Backlight Problem

Pictures so we can see all the boards and how they are connected together?

[BBN]

Re: Toshiba 32W3451DB Backlight Problem

No sure whether this is what you want - but basic overview

[tom66]

Re: Toshiba 32W3451DB Backlight Problem

Check the voltage read on those red and black wires going off to the panel - I think that is the LED backlight supply.

[BBN]

Re: Toshiba 32W3451DB Backlight Problem

If you look @ earlier message that is already there:

At present - there are two connections to the LED(s) and a DVM across this pair indicates something odd - may be pulsed DC of some form.

Red wire LED to chassis approx. +27V DC. Black Wire LED to chassis/0V approx. 1.5/2.5V DC - but again suggests pulsed or something.

[ReeceyBurger123]

Re: Toshiba 32W3451DB Backlight Problem

I would say leds on this one tbh seen it too many times on these crappy cheap led tvs, if you do find that any of the leds are shorted let me know we have replacement strips for this exact tv.

[BBN]

Re: Toshiba 32W3451DB Backlight Problem

This is my initial guess - although I do intend to try a replacement PSU PCB 1st - have been waiting for delivery, hopefully sometime this week.

If it does turn out to be the LED's how do I replace them as I cannot find any real indication of how to take apart the panel bit? I was told by another party that there was detail on 'forums' for this - but I have not seen anything yet?

[Agent24]

Re: Toshiba 32W3451DB Backlight Problem

how to take apart the panel bit?

Very carefully

[BBN]

Re: Toshiba 32W3451DB Backlight Problem

Some progress - still awaiting replacement PSU. After recent comments and looking elsewhere however - my thoughts were 'if it is a shorted LED - how can I perhaps simulate things?'

Placed a 3V9 Zener in series with the backlights and retried. Still no obvious 'lights' but now the LED backlighting drive voltage has looked to stabilize - Now RED lead closer to +72V and black line not obviously fluctuating - @ approx. 1.5V

Looks like the load the LED backlighting was placing on the drive was such that it somehow was shutting on/off - but why no backlighting still unclear?

Well that was the case for about 10 minutes now looks to have returned to original state!

[BBN]

Re: Toshiba 32W3451DB Backlight Problem

As you may expect, looks as Zener diode blown S/C.

[ReeceyBurger123]

Re: Toshiba 32W3451DB Backlight Problem

That means that the leds are bad, give me a call if you want the ones I have cheers.

[BBN]

Re: Toshiba 32W3451DB Backlight Problem

These are brief photos of the backlight strips

2 strips each with 11 leds approx. 575mm in length. and 12mm wide

Green PCB joining these is 17DB01.

Each LED strip has written upon it horizontally @ left hand end VESTEL 32 inch REV0.2 TIS-4A 94V-01346
Each LED strip has written upon it vertically @ right hand end LJ AHB2 1003 VES315 WNDL-01.

[ReeceyBurger123]

Re: Toshiba 32W3451DB Backlight Problem

Ok I have exact replacements check my pm.

[BBN]

Re: Toshiba 32W3451DB Backlight Problem

Having removed the strips I was able to wok out the connection/tracking using a DVM and two sharp scalpels to penetrate white surface of PCB/strips.

Again using DVM but set to diode test where a voltage reading is expected I was able to test each individual LED - one way round about 0.2V other no reading but very dim pinpoint of light on led connected. One LED @ one end of a strip gave no reading and no light and viewing this more carefully I think you can see a burn mark underneath it! (see attached).

I bypassed this with a 3V9 Zener diode (reverse biased) and then reconnected/repowered everything without rebuild. NOW all backlights come ON (except for bad one of course).

Hence we look to have actually found the problem, even if not cured it yet!

[budm]

Re: Toshiba 32W3451DB Backlight Problem

Looks like the same failure as this one, one LED was open, one was shorted.
https://www.badcaps.net/forum/showth...358#post566358

[BBN]

Re: Toshiba 32W3451DB Backlight Problem

Sorry this has taken so long, but I should be returning this now operational TV to its owner tomorrow.
There have been considerable delays whilst I waited for particular components to be delivered and also a week ago I thought it was OK only for a another LED to fail and cause a new repair + long periods of soaking.

As previously stated I found the initial LED culprit. I replaced this with a 1W cool white LED - which was overbright and whilst trying/testing two more LED's on that same strip gave up working - suspect mechanical failure here after strain put on glued strips when removing. I got these (and other) 1 W leds on Ebay .
Replaced all three leds and all overbright, ended up masking a bit with covers made from polyester drafting film (a bit like tracing paper) and managed to reduce screen brightness further by adding an additional led in parallel, but fastened 'out of site' on backplate chassis of TV. Refixed strips in place with double-sided thermal tape and rebuilt.
This was a bit of a compromise as now several 'bright' spots when certain colours - but I thought acceptable. I ran the rebuilt item for about 12 hours and then another LED (old one) started to flicker and then gave up O/C
Fortunately, as this LED was 2nd in from left hand bottom strip and I had already replaced 1st and 3rd in I had 'available' connections to the 'bad' one and connected a Zener diode in parallel with the second 'bad' led - this was more of a test to check the problem was still leds, rather than a repair - but I then tried things.

I do not know why, but now the two parallel back facing leds involved no longer shine, however even with the now 'missing' 2nd led in left hand bottom corner is only fractionally dim and I still have one 'bright' spot.
I have kept this arrangement, run it for more than 30 hours and it seems a good compromise.

I did find several places where I could purchase replacement LED strips - cheapest being from Romania. However, all of these were effectively 2nd hand, having been removed from 'broken units' . Having seen how much physical force was required to remove these strips I was not very keen on spending a considerable sum of cash on replacements on rather 'unknown' long term quality item. These alone would have cost me at least 10% of a brand new replacement TV.

I will state several things about my experiences here:

The LED's employed might be easy to get and replace IF you could find out exactly what make etc. was fitted.

Many led's you can purchase (like those I got from Ebay) are like beacons in comparison - I did later get hold of what are termed 0.5W rather than 1W ones, but am not keen to try these (as yet).

Taking one of these panels apart is a problematic process and you may well find it necessary to repeat things a number of times (I certainly did - at one point all looked well until in a dark room and white light was seeping out of the surround bottom). It is essential to keep the interior layers free from dust/bits etc; things must all be well aligned and there are a large number of plastic spring tabs involved that must be released/re-engaged that are very likely to snap off without care.
Just taking the back off of this type of TV involves screws and a simple lever action. Getting down to the internal led strips/panel itself requires a lot more screws + plastic clips - a lot more to get right and go wrong + disconnection and manhandling of some sensitive parts too.

Thanks to all of you who have made comments.

[Als_2014]

Re: Toshiba 32W3451DB Backlight Problem

HI to all friends here, i have same problem with this kind of strip leds, whose The first time i fixed a telefunken 32" tv that use this product of strip, i used to pull off all the strips and changed with the chinese led strip model 5050-1M/60led of a 5meter roll package modifying the electronic circuit, but it takes time and too much work, so please i ask in this forum if anybody knows where to buy each single led .. Thanks.

[Als_2014]

Re: Toshiba 32W3451DB Backlight Problem

Ok I have exact replacements check my pm.

hi, Can i ask where to buy every single led for replacement, thanks