Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

[johnedgley]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

Hi dskall, and thanks for your interest. Yes I did check and there is definitely a display, and I don't know what happened when it first went wrong but I have not seen anything from the backlights at all since I've been working on it - completely dead!

Did you check screen with flashlight or torch as you on the other side of pond call it for an image on screen? Also did backlights flash on when first turned on?

[dskall]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

Three photos here showing my values vs the reference ones on the (poor) photo - the ones with a "?" are very hard to discern on the original, in fact one seems to be missing altogether, but I've done my best, and if anyone can help pinpoint the likely cause(s) of the failure it'd be great.

Also, those ref values applied to the board when fitted to a completely different tv, i.e. powered from a different p.s.u., and I have no idea whether that would make a difference (or how much difference)

Here is data for your ic with 0v. http://html.alldatasheet.com/html-pd...2/1/SN358.html The 16v ref might be vcc for it since operating voltage is 3v-30v. I am just learning so take it for what it's worth. I think it is the oscillator for the circuit to boost voltage through the three diodes that remain at 23v I think are D101,102,103

[johnedgley]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

Thanks for that - it certainly makes sense so I shall check some more tomorrow, in fact I think I may even have a 358 kicking around here somewhere!

[dick_barton]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

It would be worth your while checking as many of the board components with your meter that you can. It does appear as though the boost circuit is not functioning as stated by dskall in post#22

[budm]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

You need to put Black probe on the chassis and leave the Red probe on the Vout pad THEN turn on the TV to see if the Voltage jumps up way beyond 24V feeding Voltage or not.
Right now I believe if there is open circuit in the LED string the Vout will jump up too high so it goes into protection shutdown so you will only see the 24V which is the input Voltage to the boost converter.

[johnedgley]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

@budm; Aha - thanks, noted, I'll check for that first

@dick_barton; also noted, tho' I'll check as per budm first

... and my thanks to all for their continued support!

[johnedgley]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

@budm; from the testing I am able to do it seems to me that you are correct. The voltage rises very briefly sometimes, though not always, and the highest I've seen is 90V.

Individual testing of the strips and LED's seems to show just one duff LED. Reading other peoples threads it also seems that I can safely jump that one (of 43) and it should (might?) all work ok... would you agree with that? I am having trouble finding the spec of the individual LED's so am not sure what else to try.

[dskall]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

Budm If you unplug led connector and measure your voltage it should rise to the max. voltage that is on the panel specs. and if it does it confirms good led supply board. Is that correct?

[vinceroger69]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

@budm; from the testing I am able to do it seems to me that you are correct. The voltage rises very briefly sometimes, though not always, and the highest I've seen is 90V.

Individual testing of the strips and LED's seems to show just one duff LED. Reading other peoples threads it also seems that I can safely jump that one (of 43) and it should (might?) all work ok... would you agree with that? I am having trouble finding the spec of the individual LED's so am not sure what else to try.

Whats the number of the faulty led strip? we can see what type of led it uses then budm has posted in a thread that you can use diodes to bridge faulty leds but i will let him explaine as i cant remember how many to use

[johnedgley]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

The faulty strip is SVS400A79_5LED_C TYPE_Rev.1_120712 - the board is a combo of types A,B,C, and D totalling 43 LED's.

Whilst searching I found;

http://www.ebay.co.uk/itm/332057189100

which he says are a suitable (or better) substitute from LG, but I what do I know!

[vinceroger69]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

That seller is fine i have used him before

[johnedgley]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

That's good to know, thanks. Just had a quick look and cannot find anything from ohms supplies but will carry on tomorrow.

[vinceroger69]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

That's good to know, thanks. Just had a quick look and cannot find anything from ohms supplies but will carry on tomorrow.

ohms what a lot dearer 1.95 each led plus vat plus postage so i removed my comment but the ebay seller seems ok too me.

[johnedgley]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

Lol - ok, so I won't go looking for them tomorrow after all!

I shall probably end up getting the ebay ones, though it would be good to get a comment from budm before buying 20 of the things...

ohms what a lot dearer 1.95 each led plus vat plus postage so i removed my comment but the ebay seller seems ok too me.

[vinceroger69]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

Lol - ok, so I won't go looking for them tomorrow after all!

I shall probably end up getting the ebay ones, though it would be good to get a comment from budm before buying 20 of the things...

https://shop.strato.com/epages/62027...ts/LED11-Y6.01

if one leds gone i bet others will follow soon so always best have spares.

[johnedgley]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

Good point!

Thanks for the link however it confirms I certainly wont go to Ohms - not only a wicked price but also a dreadful site! It says 2012 and is more like turn of the century... "To know how much an order will cost including tax and postage you can simply add any number of products to the shopping basket, you will not be able to see the total cost but will not be able to place the order." and "At Ohm we believe that engineers can repair almost anything providing the parts, knowledge and tools to do this are available to do this"

https://shop.strato.com/epages/62027...ts/LED11-Y6.01

if one leds gone i bet others will follow soon so always best have spares.

[vinceroger69]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

Good point!

Thanks for the link however it confirms I certainly wont go to Ohms - not only a wicked price but also a dreadful site! It says 2012 and is more like turn of the century... "To know how much an order will cost including tax and postage you can simply add any number of products to the shopping basket, you will not be able to see the total cost but will not be able to place the order." and "At Ohm we believe that engineers can repair almost anything providing the parts, knowledge and tools to do this are available to do this"

ohms are good on a lot of stuff a few of use use them for eeprom dumps etc and ics etc, i can see the total price etc but i guess its because im registered and have used them a fair few times quick delivery too just some parts are a little expensive at times but same with most shops i guess.

[budm]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

Budm If you unplug led connector and measure your voltage it should rise to the max. voltage that is on the panel specs. and if it does it confirms good led supply board. Is that correct?

Think of it the same as when you want to hook up the Power supply to the LED withe require current through the LED, you will have Vf of the LED + the Vdrops of the current limiter resistor so that is what the minimum Power supply has to put out..
The power supply for the LED in TV is more complicate because you have to be able to maintain the set current.
The output Voltage of the Power supply has to be higher than the total Vf of the LED as specified in the panel spec, the power supply has to be able to supply the minimum VF + Vdrops on the PWM Controlled MOSFET (typcal value is from 20~35V range, depends on the design of range of the Constant current power supply) + Vdrops on the Current sensing resistor.
If you also look at most power supplies with the printed Output Voltage and current, those number are with load, if there is no load the output will rise since it's trying to maintain the constant current through the load no matter what the load resistance but it can only go up so high by design requirement.
The Voltage applied to the load in Constant current power supply will be varied to maintain constant current.

[johnedgley]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

@budm; re my #27 & #30, could I press you on what you think about the psu output I recorded (very briefly 90V) and possibly bridging the duff LED? And also the possible substitutes mentioned (http://www.ebay.co.uk/itm/332057189100) ...

[pedro89]

Re: Technika 40-E271 TV with TP.MSD309.BP86 Mainboard

Hello.

I have a Philips 40PFL3107H/12 which had the same issue and similar values on the driver board. Sometimes when turned on the backlight would flash very briefly so I assumed that the LEDs are OK. Ordered a new driver board, replaced it, the issue remained.

I took a closer look and better measurements and found that this:



is a bad connection. So I did this disgusting solder work:



aaand its working again.