Samsung ps-50q7hd - No display or sound

[WallArt-Online]

Hi,

I have a Samsung ps-50q7hd i turned the unit on and could instantly smell an electrical burning smell, there is no display or sound coming from the tv. the power led flashes when turned on but does not make the start up chime.

I have had the back off the unit and could not see any obvious damage or bulging capacitors.

What tests can i do to the unit to identify the fault?

Many thanks

Steve

[mohomane]

Re: Samsung ps-50q7hd - No display or sound

visual test first and voltage testing.

[tom66]

Re: Samsung ps-50q7hd - No display or sound

Have you attempted to locate the source of the burning smell?

[capkid]

Re: Samsung ps-50q7hd - No display or sound

If you haven't already, I'd thoroughly scan the boards with a flashlight to see if you can locate a burned component. I've missed bad components without a flashlight.

[WallArt-Online]

Re: Samsung ps-50q7hd - No display or sound

I will have another look, Thanks

[WallArt-Online]

Re: Samsung ps-50q7hd - No display or sound

Had a look at the tv today, found some burnt out components on the y-main board, should this be a simple replacement?

[capkid]

Re: Samsung ps-50q7hd - No display or sound

Here's a repair kit for this Y-main that includes the burned components: http://www.ohmsupplies.co.uk/REPAIR-...MSUNG-PS50Q7HD

You may want to try disconnecting the Y-main from the power supply to see if the TV powers up fully with a chime then measure your PSU output voltages. Be sure to wait at least 5 mins before you reconnect the Y-main to the PSU should you decide to do so.

Edit: I'd replace ALL the components included in the kit, not just the obviously burned components. Also, I'd hit the boards with a spray duster while you have the TV open.

[WallArt-Online]

Re: Samsung ps-50q7hd - No display or sound

Hi, Thanks for your reply, before i commit to ordering the repair kit i would prefer to be able to replace the whole thing as my soldering skills are not very good, would i need the exact same part number as there is one on ebay but it has a slightly different number. mine is LJ41-04516A REV1 thee ebay one is LJ41-04084A R1.0 LJ92-01391A

[capkid]

Re: Samsung ps-50q7hd - No display or sound

You'll want to match part nums. Search for your original part on shopjimmy.com to see if there are any substitutes listed in the description.

[capkid]

Re: Samsung ps-50q7hd - No display or sound

I don't know how I forgot to mention this, but you'll want to test your Y-buffers for shorts BEFORE you replace the Y-main: http://www.youtube.com/watch?v=51SZsfH60EY. Since the Y-main failure is common with this TV, I'd strongly suggest you buy a Y-main from a company that offers at least a 3-month warranty, or I'd use a reputable repair service.

[WallArt-Online]

Re: Samsung ps-50q7hd - No display or sound

Hi again, i did the buffer test they tested ok. I have received my repair kit today but when i heated the damaged components to remove them the circuit board underneath lifted up it looks really burnt from when the diodes where burning. as such this leaves no contact point for installing the new diodes. is this board dead or still repairable?

[tom66]

Re: Samsung ps-50q7hd - No display or sound

Post a pic of the problem - most cases it can be fixed with some creativity.

[WallArt-Online]

Re: Samsung ps-50q7hd - No display or sound

This is after i removed some of the diodes..
http://img36.*************/img36/2448/qlq.JPG

This is the fix i did ( i have reversed the way the diodes go as the other way did not work.. neither does this way)
http://img15.*************/img15/5679/ctg7.jpg

Since changing these the tv just clicks on and off and the power led flashes.

Any ideas what could be wrong? if i disconnect the yboard the tv chimes.

[tom66]

Re: Samsung ps-50q7hd - No display or sound

That looks difficult to fix - reversing the diodes may have caused more damage.

[Dang]

Re: Samsung ps-50q7hd - No display or sound

You may want to watch this: http://www.youtube.com/watch?v=R5mYKAgMoB4. I suggest using lead type through hole diodes, this will bypass the damage and may give you a working Tv.

[WallArt-Online]

Re: Samsung ps-50q7hd - No display or sound

I have reversed the diodes back around. is there any other checks i can do such as voltage checks

[tom66]

Re: Samsung ps-50q7hd - No display or sound

You can run it without the buffers and check the Vscan voltage point.

[WallArt-Online]

Re: Samsung ps-50q7hd - No display or sound

Thanks for all you help so far,

I have not yet checked the voltages as the tv is not with me at the moment.

I have did not replace the 10 chips in the kit, i have done this check on them not sure if this is the correct way to test them.

See the below picture, all of them read 0.21 on the multimeter apart from the one i have marked red this reports OL. when i remove this one from the board all the others then read .870+.


Upon that test i presumed the it was bad and wanted to replace it, but after i removed the pins from the board it appears stuck to the board. is there a trick to removing these?

Also could you confirm i have the zenner diodes in the correct way (picture below)




Many thanks for all you help.

[WallArt-Online]

Re: Samsung ps-50q7hd - No display or sound

bump

[WallArt-Online]

Re: Samsung ps-50q7hd - No display or sound

Ok, i have put the board back in today, i replaced that bad mosfet, but the tv did the exact same thing, so i attempted to get the Vscan voltage.

I did this on the yboard side not on the psu, im not sure if my meter was making a very good connection as they have plastic all the way to the very end. i got a reading of -0.80 down to -0.30 when i powered the unit on at the wall.

if the reading i got was correct could it be an issue with the psu?