BUSH 42" LED TV. BLED42FHDAE Completely dead. Diagnosed and solution awaiting parts..

[PsiDOC]

HI all. Just a note for anyone that has one of these TVs.
Make: Bush (China)
Model: BLED42FHDAE.
Symptoms: Half screen went dark, then tv wend dead. No power lights. Fuse checked ok.

First thing checked was standby 5v: Present @ 5.1v.
PS_ON signal from main board: Present @ 4.5v.
I suspected the power supply to be in a foldback / crowbar condition after the screen going out, so I disconnected the power to LED Backlight board (Part ER643). Now standby light is on and TV responds to remote power on - light goes green.
Disconnected the LEDs from the backlight board and reconnect power. TV dead.
Time to pull the backlight board - pics below. You can see the problem immediately. One of the shunt mosfets has basically fried itself and was short circuit.



Also the high voltage Schottky diode was short circuit as well, which I think was the initial problem and the mosfet gave it's life trying to control the wayward Schottky, until it fried, went short circuit and then the power supply stepped in and shut the whole lot down.





The LED Driver board has 2 pretty much identical circuits - one for each half of the screen - that boost the voltage from 24 volts to 45 - 90 volts depending on brightness to illuminate the LED strings so by disabling the bad half I was able to power up the TV and test both halves of the screen LEDS individually. Fortunately both check out @ 370ma @66v so all good there.

Now, here comes the problem.
I could replace the failed mosfet and the schottky for a few £s but the only place it seems I can get them is in China via EBAY. I don't want to go down that route as you never know what part you are getting even if the number on it is the right one.
Also the PCB copper cladding has lifted where the mosfet tab (drain) is soldered to the board so losing some of it's thermal conductance and possibly shortening the lifespan of the component.
I'd love to replace like for like but this LED driver board - ER643 - is not available anywhere!
It seems that my only option currently is one of these "universal" LED driver boards available from China. I have found one that does 500ma constant current settable in 50ma steps and can vary between 80 and 160 volts on the adjustment input pin.
So the plan is to use one of these and series up the 2 LED halves of the screen so that I can run at 125v and 370ma.
It's not ideal, but it should work.

Opinions please?
Cheers.

[diif]

Re: BUSH 42" LED TV. BLED42FHDAE Completely dead. Diagnosed and solution awaiting par

Whilst there's no doubt some of the parts are total garbage the vast majority are not. If you were producing expensive devices then definitely avoid but for hobby and repairing most are fine.

You're cheap power supply from China isn't going to be made of any better components.

What components are blown, I don't think you detail them.

[PsiDOC]

Re: BUSH 42" LED TV. BLED42FHDAE Completely dead. Diagnosed and solution awaiting par

You're cheap power supply from China isn't going to be made of any better components.

You are probably right, however at least the components will actually be close to what they should be.
I have had components come in from the land of the rising yuan that are clearly fake as I could see the etching of the original part number under the number printed on top of it and yes it didn't work.
This has put me off buying components from non reputable sources and in particular from foreign shores on Ebay.

What components are blown, I don't think you detail them.

You are right. I didn't - sorry.
The Mosfet is a STU15L01.
The Schottky is a SB3B0.

Cheers.
Si

[cheeky2]

Re: BUSH 42" LED TV. BLED42FHDAE Completely dead. Diagnosed and solution awaiting par

Personally speaking I would order a couple of the mosfets in question from China.
If your concerned over the heatsink capabilities of the mosfet relocate it to another part of the same area of the copper and scrape the coating off of it to give you a good bond when soldering on to it. Then run a couple of soldered wires to the relevant pads in question.
That should resolve your issue with the heat.
I agree the quality and the fake items received from China are a joke but I would work with what you already have.

[PsiDOC]

Re: BUSH 42" LED TV. BLED42FHDAE Completely dead. Diagnosed and solution awaiting par

Personally speaking I would order a couple of the mosfets in question from China.
If your concerned over the heatsink capabilities of the mosfet relocate it to another part of the same area of the copper and scrape the coating off of it to give you a good bond when soldering on to it. Then run a couple of soldered wires to the relevant pads in question.
That should resolve your issue with the heat.
I agree the quality and the fake items received from China are a joke but I would work with what you already have.

Cheeky, I took your advice and ordered the components and relocated the MOSFET on the PCB.
The TV is now working as it should and back in service.
Thanks for the advice. It's appreciated.
Regards,
Si