Samsung model # PN43D450A2D Black Screen Red Light

[ttt9090]

Hi all,
I'm attempting to diagnose a 42" Samsung Plasma model # PN43D450A2D with black screen red blinking light.

When I plug it in, it exhibits the typical relay clicking a few times and nothing on screen, nor any sound.

Visual inspection shows no signs of bad caps leaks or bulging or any other visual overheat issues.

If I dis-connect either the x or y board it makes the "samsung" sound and responds to remote turn on / off, but still nothing on screen.

I checked the single ceramic fuse for ohms with power off and it seems fine.

I pulled the y board to inspect the back for visual issues and see none.

I'm fairly new to this tv stuff, so was hoping for someone with the time, to walk me through this in terms of where should i begin to test for voltages etc.

I can provide pictures along the way if needed and have a couple of basic digital multimeters and a general knowledge of how to use them.

Thanks for looking and hope to hear from someone soon.

Cheers,
TTT

[tom66]

Re: Samsung model # PN43D450A2D Black Screen Red Light

You have an X-main failure, very common on this model. Remove the board, check the LJ92-xxxxxx part code, and find one on ShopJimmy/eBay etc.

[ttt9090]

Re: Samsung model # PN43D450A2D Black Screen Red Light

Wow that was quick Tom66, thanks.

Forgot to mention before, that I also followed one of your guides on jumpering the controller board for test patterns and had no luck.

I pulled & checked the x-main the number on it is LJ41-09478A LJ92-01796A R1.6.
Found one on ebay for $30 that's the same except LJ41-09478A LJ92-01796A R1.8. I assume that is a revision number of one with better components?

P.S.
Just because I'm interested... Can you point me at any values for this boards components that I could reference to do some tests with my MM so I can see what went wrong? I know it's probably not worth the effort to someone being paid for their time, but I have lots to waste and am fascinated with all this stuff and figuring out why it does or doesn't do what it's supposed to.

Thank you so much for the excellent resources and videos you have provided. I've mostly been into pc repair for a long time and have re-capped a few motherboards over the years and tried my hand and re-flowing some gpu's etc., but this tv stuff, is new ground for me.

Love the forums and I'll be sure to watch out for anyone with issues I may be able to help with.

[ttt9090]

Re: Samsung model # PN43D450A2D Black Screen Red Light

Oops...
In my original post, I mentioned that "If I dis-connect either the x or y board it makes the "samsung" sound and responds to remote turn on / off, but still nothing on screen."

I just went through it all again to double check and I realized I was mistaken.
In fact, it does not make the sound when the Y-main is plugged in, only if the Y-main, or both are dis-connected.
I don't know if this makes any difference to the diagnosis and I apologize for my error.

[capkid]

Re: Samsung model # PN43D450A2D Black Screen Red Light

Oops...
In my original post, I mentioned that "If I dis-connect either the x or y board it makes the "samsung" sound and responds to remote turn on / off, but still nothing on screen."

I just went through it all again to double check and I realized I was mistaken.
In fact, it does not make the sound when the Y-main is plugged in, only if the Y-main, or both are dis-connected.
I don't know if this makes any difference to the diagnosis and I apologize for my error.

I'm not sure if this is a surefire way to find the fault, but it seems consistent in the five Samsung-based thin-profile TVs I've worked. Like I mentioned in another thread, I wouldn't tinker too much with this TV, as you could end up damaging other components during testing:

I'd test the Y-main's and X-main's through-hole transistors on the heat sink and the fuses with a multimeter. Usually when one of the "mains" is damaged, one or more of the through-hole transistors on the heat sink is bad. Remove the boards from the TV to perform the tests:

- If any of the Y-main's through-hole transistors on the heat sink or the fuse are bad, replace the Y-main and Y-buffer AS A SET.
- If any of the X-main's transistors on the heat sink or the fuse are bad, replace the X-main. Some of these thin-profile TVs also have an X-buffer; if the X-main is bad in this case, replace the X-main and X-buffer AS A SET.

When your replacement board arrives, repeat the transistor and fuse test on the replacement "main" board, connect EVERYTHING up in the TV AT ONCE, then power it on.

[ttt9090]

Re: Samsung model # PN43D450A2D Black Screen Red Light

Thanks Capkid,
I'll see what happens.

[tom66]

Re: Samsung model # PN43D450A2D Black Screen Red Light

If you find that disconnecting the Y-main works only, then the Y-main AND/OR the X-main are bad, due to the power chaining scheme.

There are very few through hole devices on these boards. It's mostly done SMD. The only through hole devices are the energy recovery (ERC) fet and diode. However the testing method is the same.

If the Y-main is replaced, the Y-buffer should also be replaced on these models.

[ttt9090]

Re: Samsung model # PN43D450A2D Black Screen Red Light

Thanks Tom66,
I have advised my friend (tv owner), that I'm a bit leary of spending his money to buy parts unless I can be 99% certain that I have found the culprit component.
Will keep you all updated though when we decide on course of action so as to help others.

[capkid]

Re: Samsung model # PN43D450A2D Black Screen Red Light

If you find that disconnecting the Y-main works only, then the Y-main AND/OR the X-main are bad, due to the power chaining scheme.

There are very few through hole devices on these boards. It's mostly done SMD. The only through hole devices are the energy recovery (ERC) fet and diode. However the testing method is the same.

If the Y-main is replaced, the Y-buffer should also be replaced on these models.

In your experience, have you found that one or more of the through-hole components on the heat sink is shorted when the Y-main or X-main fails in these thin Samsung TVs?

[tom66]

Re: Samsung model # PN43D450A2D Black Screen Red Light

Usually just the SMD fets. However, I have only done one of the D-series plasmas which use almost entirely SMD fets.

[ttt9090]

Re: Samsung model # PN43D450A2D Black Screen Red Light

Hi again,
My friend put the new y board in and it has stopped clicking, it only clicks a couple of times when he first plugs it in and pauses and clicks a couple more times then stops, red standby lights stay on and no clicks after that.
Where to look next?
Thanks for the help

[dh3292]

Re: Samsung model # PN43D450A2D Black Screen Red Light

I have the same fault as the original thread question but my standby light remains red when relay clicking. I removed the back tested fuse and measured 220v @ fuse. I also have a green led flashing on the small board at the bottom.

Help much appreciated

Thanks

[lcdman]

Re: Samsung model # PN43D450A2D Black Screen Red Light

Hello All

I have this same model tv. I was removing one of the four fets that are part of this tv's x main board common failure. In the process I had a resistor pop off the board. Its board location is r4022. Its so small that I can't locate it. Perhaps someone here knows the value of the this missing resistor?

Thanks In Advance,
lcdman

[R_J]

Re: Samsung model # PN43D450A2D Black Screen Red Light

It should be the same as the one next to it, (150) 15 ohm. You need to do a better job removing those transistors, you ripped the traces under them. that can effect their heat transfer during operation. Try adding flux and more heat next time

[lcdman]

Re: Samsung model # PN43D450A2D Black Screen Red Light

Hello RJ

I wondered if it had the same value as the one next to it. (150) 15 ohm. What
rating/tolerance would you guess it is? Size type? 1206 as an example. This was my first repair attempt using a hot air gun. I will take your advice though for next time.

Thanks,
lcdman

[tvtimmy]

Re: Samsung model # PN43D450A2D Black Screen Red Light

The way to remove the surface mount fets is:
1. Add fresh leaded solder to both legs. If you have a thin tip, go behind the legs and heat the pad and pry up. You can use a pick also, just make sure solder is molten.
2. Then add some solder to the main pad and heat the crap out of it. Dont use a heat gun, you will only f#%@ things up. It will lift right off when hot enough.
3. To replace the fets, put some fresh solder on the main pad, and when molten, place new fet in place, using tweezers. Flow some solder over the tab, then solder down the legs. This way you shouldnt rip off traces.

[lcdman]

Re: Samsung model # PN43D450A2D Black Screen Red Light

Hello Again,

(150) 15 ohm. What rating/tolerance would you guess it is? Size type? 1206 as an example. I just want to be sure before trying to source a replacement resistor.

Take Care,
lcdman

[R_J]

Re: Samsung model # PN43D450A2D Black Screen Red Light

You would have to measure the size, I can't, I'm sure 1/4 watt or 1/2 watt would be fine

[tom66]

Re: Samsung model # PN43D450A2D Black Screen Red Light

It's 1206, I've repaired a few of these now
If the resistor popped off the board it might be bad, so check its cousin is not open circuit
If that's open circuit you'll almost certainly have to replace the driver IC for them. In fact I'd generally recommend it anyway unless you can be sure its OK as it might just pop the new IGBTs again.