Samsung PS-50Q97HD Black screen, No sound

[Bridgie999]

Hi,

My 2007 Samsung 50" has developed the problems of black screen & no sound. After a little research I came upon the problem of rogue capacitors, however, when I removed the back of the TV, no capacitors have blown top or bottom or show any kind of distortion.

The only sign of any spillage from any components is what I can only describe as a sort of white glue that is on some components. It looks though it has been applied during production, I'm sure someone will know if this normal or the cause of my problems.

Other information is that the TV starts on remote, there is one click and then the start up tone comes on. 3 green lights come on behind one of the boards (one of them winking on and off).

The TV stays on for about 15mins and then turns itself off. In that time all the heat sinks on the power board are warm to hot and most are, on the X,Y boards.

I am hoping it is still a capacitor problem but would welcome any ideas or suggestions (apart from using it an expensive door stop!!!)

Finally, I have bought a test unit to test the capacitors, do they have to be removed from the boards to test or can I test them in situ.

Many thanks, I can post photo's if required

Bridgie

[drpj23]

Re: Samsung PS-50Q97HD Black screen, No sound

I must ask if this was on another input like HDMI, if so then there will be no sound. The reason I ask is because there is a start up sound and if there is no signal then some sets will shut off.

Check to make sure all the voltages from the P/S are correct...so check Vs, Va, -VY, VSC. (last two are on YSUS board). I also think there should be like a SET_UP and Z-BIAS voltage. (all of this is on a sticker on the panel)

Also check the LVDS cable.

The white glue is from production...most likely a security glue.

The green lights are normal and is most likely on your controller board...the blinking one acts as a temp guage.

Caps do have to be tested out of circuit.

And yes post photos.

[tw2005]

Re: Samsung PS-50Q97HD Black screen, No sound

Sounds like shorted y buffer and blown y-sus. Can you post some pictures of the ysus and buffers.

If this model is related to a PS50Q91HD then I know they will power save and shutdown if no signal is present for a period of time. Mine did.

I think from memory if you connect a source in and select av in they auto detect the source. maybe try it and see if you get audio.

[tw2005]

Re: Samsung PS-50Q97HD Black screen, No sound

Blown FETs usually on this heatsink . 88N30W. One of these shorted will short out all the other 88N30W. I don't have this board anymore to take a high res shot.

[Bridgie999]

Re: Samsung PS-50Q97HD Black screen, No sound

Hi Guys,

Sorry for the delay in posting Pics. However I have taken some of the ? main power board where I thought the problem may be and I will post pics of other boards in the next couple of days. please bear with me if I ask stupid seeming questions, as you can probably guess I'm not a TV engineer just a reasonably handy guy who's jacked off at paying out €1800 4 years ago and now I have got an expensive door stop. If you think you have customer service probs in the US or Oz try living in Spain. Anyway any help or suggestions gratefully received----i have my capacitor tester and solder remover etc; but will hold fire removing goods until further advice. Thanks Bridgie

[drpj23]

Re: Samsung PS-50Q97HD Black screen, No sound

Wait, what are the voltages coming from that power supply?

Two, your main power supply is probably fine and as tw2005 stated, the problem most likely resides in the Y section of the TV. The fact you have sound/cuts on and does not go into a protect circuit is the reason for that diagnosis. Two you also may have a blown fuse on the YSUS, so check for that as well, which will be a good giveaway.

[Bridgie999]

Re: Samsung PS-50Q97HD Black screen, No sound

Wait, what are the voltages coming from that power supply?

Two, your main power supply is probably fine and as tw2005 stated, the problem most likely resides in the Y section of the TV. The fact you have sound/cuts on and does not go into a protect circuit is the reason for that diagnosis. Two you also may have a blown fuse on the YSUS, so check for that as well, which will be a good giveaway.

Damn, just seen your post. Thank you hotmail for not notifying me of your reply.

Heyho it's rare rainy day here in Spain so I amused myself taking out capacitors from the power board and testing them. The four were all 1000uf 3 tested 1040ish and one 980. Then I saw your post and thought --Doh fuses. Sure enough the fuse on the YSUS has failed. Is this fixable or is it a case of buying a replacement YSUS and will this definitely fix the problem. I saw 50" TV's in our local store yesterday for €600 so I don't want to spend too much. Having said that I am enjoying the challenge.

Now the idiots questions how do I test the voltages? I may need a step by step guide here but in the meantime I'll be soldering capacitors back in tomoz

ps. All the other fuses are fine.

Thanks.

[drpj23]

Re: Samsung PS-50Q97HD Black screen, No sound

It can be either. As tw2005 said in post 4, your FETs have probably shorted out.
If you want your TV back quicker then buying a YSUS is usually under $100....err 80 euro perhaps......and it should fix your problem. But with this problem, we cannot see other problems that could be there.... but that is probably not your case.

For checking voltages, get a digital multi meter and put the black probe on ground (chassis or screw) and the red probe on the corresponding pin that you are testing. If you have to set ranges, make sure the voltage on the meter is higher than what you are checking and make sure the meter is set to DC (not the squiggly).

Check the FETs this way. ((As per the 2 seconds to black sticky))

If you have a manual range multimeter, set it to 200 ohms (two hundred). You can test for shorted transistors "in circuit" (with power off and unplugged)

a) put black probe on pin 1 and red probe on pin 2 - read/record ohm
b) put black probe on pin 1 and red probe on pin 3 - read/record ohm
c) put black probe on pin 2 and red probe on pin 3 - read/record ohm

If any reading is less than 30 ohms you might have shorted transistor. Remove the transistor and repeat the tests out of circuit to verify.

[Bridgie999]

Re: Samsung PS-50Q97HD Black screen, No sound

Sorry for the delay in reposting--a month since my last post!!! that's the time it's taken to get solder and flux suitable for TV's and the fuses for the Y-sus.
Rebuilt the power supply today and replaced the blown fuse in the Y-sus and with trepidation turn the set on----three green light came on and then click it went off and click back on, click off, click on etc; etc. tested the fuse on the Y sus to see if it had blown--no.
Disconnected the Y-sus and turned back on---set fires up complete with the "Diddlydoo" tune and stays fired up.
Power off. Connected Y-sus
Click on, click off, click on , click off etc; etc;

So the problem seems to be the Y-sus, has anyone any ideas as to what is my next step should be or even better the definitive answer to what the problem is.

Many thanks
Bridgie

[tw2005]

Re: Samsung PS-50Q97HD Black screen, No sound

Can you tell us what you've replaced and tested on the ymain + pictures.

Also are you running the original buffer boards? If so probably not a good idea. I found on all 3 tvs with dead ymain the upper buffer was bad also.

I mentioned the buffers in post #3

[Bridgie999]

Re: Samsung PS-50Q97HD Black screen, No sound

Can you tell us what you've replaced and tested on the ymain + pictures.

Also are you running the original buffer boards? If so probably not a good idea. I found on all 3 tvs with dead ymain the upper buffer was bad also.

I mentioned the buffers in post #3

Hi TW,

I wouldn't know what a buffer board was if I tripped over it I've replaced nothing but I have unsoldered, tested and resoldered all the capacitors on the power board to check their OK and then I replaced the blown fuse on the Y board????. I've replaced nothing else and have tested nothing else.

[tw2005]

Re: Samsung PS-50Q97HD Black screen, No sound

Ok well that's most likely why you have not made any progress.
You need to test the transistors on the board where I circled earlier for shorts.
The buffers are the 2 long boards which are connected to the ysus.
Test first and post results

[Bridgie999]

Re: Samsung PS-50Q97HD Black screen, No sound

Ok well that's most likely why you have not made any progress.
You need to test the transistors on the board where I circled earlier for shorts.
The buffers are the 2 long boards which are connected to the ysus.
Test first and post results

Will do. We are of to Oz for xmas, hopefully I will have time before we go. Thanks for your interest.

[Bridgie999]

Re: Samsung PS-50Q97HD Black screen, No sound

Ok,after a crash course from U tube on testing Diodes and Transistors here are the results for the FET's that you highlighted in post three. I tested the FET's in situ and because I didn't know which leg was which I tested each pin in every combination I.E.

1 2 3
R B x
B R x
R x B
B x R
x R B
x B R

Where B & R are the black & red probes of the multimeter which was set to test diodes and when setting the function to test the diodes a No 1 showed on the screen.

FET 1 FET2 FET3 FET4 FET5
0.47 0.97 0.97 0.97 0.005
0.47 0.98 0.97 0.97 0.005
0.46 0.97 0.97 0.97 0.005
0.47 0.97 0.97 0.97 0.005
0.001 0.001 0.001 0.001 0.001
0.001 0.001 0.001 0.001 0.001

I fear the worst. Am I right in assuming that as so many of the values are the same that all the FET's are shorted or--as is quite possible I have carried out the test incorrectly.
Any advice gratefully accepted.

[speedypro]

Re: Samsung PS-50Q97HD Black screen, No sound

Blown FETs usually on this heatsink . 88N30W. One of these shorted will short out all the other 88N30W. I don't have this board anymore to take a high res shot.

Hi

I have this issue where no sound no picture. The heatsink you circled, my FETs tested ok. Under the other heatsink, a FET marking K2837 is shorted compared to the other under the circled heatsink. Do you think that causes my issue?

[tw2005]

Re: Samsung PS-50Q97HD Black screen, No sound

Any shorted FET on the Ymain will be an issue, problem though is the upper buffer boards short too and are not cheap or easy to get anymore.

I'd check the buffer boards first for shorts, if they were ok then consider repair /replace the ymain.

There may be something in Toms video , same panel.

https://www.youtube.com/watch?v=25HT...tCVe9&index=13

[sgreen2004]

Re: Samsung PS-50Q97HD Black screen, No sound

Hi tw2005 i don't know if i'm posting in the white section but i have the tv in question samsung ps50q97hd and i am facing some very annoying problems, i had the very common sound but no picture so i opened the tv and found that the power coming from the psu was all normal so changed it anyway as have lots of spares and nothing so came to the decision that the ymain and buffers are to blaim so checked the IC chips on the upper buffer and one had a (c) like symbol burned into it so i checked the rest and they all looked ok but i'm unsure how to test them :/ i changed the blown IC chip (with great trouble) and replaced all 5 fets on the small heatsink for the upper board along with 2 resistors, 2 capacitors and a zenor diode, also another small fet, i now have a picture! but hers where it gets interesting its very snowy with very thin black lines however i can access the menu, if i run the tv on the bottom buffer the bottom of the screen glows purple (dark) and if i connect the top buffer and bottom as i said it works but the psu gets very very HOT and makes a loud buzzing noise although appears to be partly working. any idea's please would be greatly appriciated! steve