Samsung PS42A450P2 plasma screen problem

[mrbigsteel]

My plasma TV picture started having problems all at once. Not sure how to describe it, so I attached some photos.

Photo 1 = Apple TV home screen
Photo 2 = The Simpsons. You can kind of make out Marge.
Photo 3 = Homer Simpson with my cable provider's overlay (AT&T Uverse)
Photo 4 = TV model sticker from the back.

Any advice as to where the problem may be and if this is worth trying to repair? I'm comfortable with basic electronics and would be willing to open it up and see if I can figure it out. Am just wondering if anybody can say "Oh, the problem is probably with x, y or z."

Thank you.

[drpj23]

Re: Samsung PS42A450P2 plasma screen problem

I want to say main or controller since that processes video signal and the way it's displayed on the screen (firing order). Of course, you can try re-seating the LVDS cable.

[tom66]

Re: Samsung PS42A450P2 plasma screen problem

Is something like the volume control or main menu affected?

It looks very similar to having the LVDS panel setting incorrect.

Try this factory reset technique:
- TV in standby
- On remote: INFO, MENU, MUTE, POWER
- TV should power up
- Select "Reset" or "Factory Reset" - it may be hidden under the "Adjust" menu. Careful not to touch anything else for now.
- After selecting reset, TV should turn off - if not turn it off.
- Then turn it on again.
- Perform the first time install again, and see if picture is OK.

If that doesn't work take a picture of the service menu and we can look for the panel setting option.

[mrbigsteel]

Re: Samsung PS42A450P2 plasma screen problem

Tom66: The volume seems fine.

I tried the procedure that you suggested. The screen that appears when the TV turns on is unintelligible, so I don't know what to press to reset it. See the attached photo.

Thanks.

[cadiman]

Re: Samsung PS42A450P2 plasma screen problem

Going by the first pictures it looks like you have bad surface mount caps on the video processor board.or most likely one of the large processor chips.

Sometimes pressing on these lightly corrects the picture. They may be hot also.

I am not sure if that is part of the main or tuner board on this model.

[mrbigsteel]

Re: Samsung PS42A450P2 plasma screen problem

I reseated the LVDS cable, but it did not help. Thanks for the suggestion Drpj23.

Cadiman, all the capacitors "look" OK, but I've not tried pressing them yet.

Based on my reading of some Samsung plasma TV service manuals (none of which were for my exact model of TV), I think the problem is in the main board or in the logic board...and that it is more likely the logic board. I think drpj23 and cadiman are pointing to the same area, using different terminology?

For some Samsung plasma TV's there is a way to isolate the logic board from the main board and to display a test pattern that is generated within the logic board. If the test pattern displays correctly, it means the main board is bad. If the test pattern display incorrectly, the problem is in the logic board or further down the line between the logic board and the screen.

Normally one can display the test pattern through the service menu (press Info, Menu, Mute, Power), but my screen just displays gibberish when I access the service menu (see my 2nd post) so I can't maneuver through menus that I can't see.

Alternative: There is a hardware-based method to display the test pattern on some Samsung TV's. It involves shorting some pins on the power supply and shorting some other pins on the logic board. I am not sure if my TV supports this and I don't have the nerve to try it yet. Has anyone here used that method before?

[mrbigsteel]

Re: Samsung PS42A450P2 plasma screen problem

Attached is a PDF of the hardware-based method that I was referring to in my previous post.

Does anybody have any experience doing this?

[tom66]

Re: Samsung PS42A450P2 plasma screen problem

Crashp3 has some experience with this - I believe it's pins 3 & 4.

[mrbigsteel]

Re: Samsung PS42A450P2 plasma screen problem

Part of the procedure to force the logic board to display the test pattern is to short the "PS_ON" and "GND" pins on the 24-pin connector that goes between the power supply and the Main Board.

My connector doesn't identify a "GND" pin. It has a "PS_ON" pin, but no "GND" pin is identified. Any suggestions as to which pin I should use? Is "RTN" the same as Ground?

Photos are attached.

[drpj23]

Re: Samsung PS42A450P2 plasma screen problem

Yes RTN would be your ground.

[mrbigsteel]

Re: Samsung PS42A450P2 plasma screen problem

Thank Drpj23. It worked! The TV turns on and the display cycles through a number of test patterns and repeats the pattern in an infinite loop.

The patterns are not as complex as I expected them to be: All white, all red, all green, all blue, scroll up white, scroll up red, scroll up green, scroll up blue, scroll left yellow, diagonal white, repeat. All screens, colors and transitions were clean.

So that means that the Main Board is bad, since it is the only board that was removed from the system with this test.

Here is the procedure for anybody else who wants to try this (you assume all risk):

1) Unplug your TV.

2) Disconnect all cables that go to the Main Board.

3) Find 24-wire ribbon cable that goes between the Power Supply Board and the Main Board. Jump the PS_ON and RTN pins on the connector at the Power Supply Board. See photo. (Note that the other end of this cable should be disconnected from the Main Board per step #2.)

4) Short pins 3 and 4 on the quad connector of the Logic Board.* I used an alligator clip to do this. See photo.

5) Plug your TV back in. The TV should turn on automatically and start playing the test pattern.

* Bonus question: Does anybody know what would happen if you jumped pins 1 and 2 instead of 3 and 4 on the logic board? Would it display a different pattern? The pins are labelled as follows:

1.2 PAL(IN) ST(OUT)
3.4 SCR(IN) ST(OUT)

[tw2005]

Re: Samsung PS42A450P2 plasma screen problem

Looks like a corrupted EEPROM. I noticed when you did it it displayed HDMI. If you have the set hooked up on a tv channel and watch it then try going into Factory menu what do you get?

your picture looks very similar to this Chinese special .

https://www.badcaps.net/forum/showth...&highlight=mvm

[mrbigsteel]

Re: Samsung PS42A450P2 plasma screen problem

Tw2005: I don't know how to access the factory menu when the TV is turned on and displaying a TV channel. The only procedure I know is for when the TV is in standby (press Info, Menu, Mute, Power). Does anybody know how?

You fixed your TV with a "factory reset". If I could see the factory menu, I would try the same. Tom66 suggested this earlier.

[vinceroger69]

Re: Samsung PS42A450P2 plasma screen problem

SOURCE" FOLLOWED BY 2580 WITH THE SET ON. should work as per tw2005 link

[tw2005]

Re: Samsung PS42A450P2 plasma screen problem

SOURCE" FOLLOWED BY 2580 WITH THE SET ON. should work as per tw2005 link

I don't think it will. try it I guess but that was for some chinese thing.

I guess what I mean is I see you get some kind of tv picture. Set the TV up as if you are watching then retry that remote sequence.

On the 2 samsungs I played with I'm pretty sure the service menu came up withthe picture running in the background.

On your picture it showed HDMI and I'm assuming that was the last input the TV was running on or selected.

Is that correct or not?

[tw2005]

Re: Samsung PS42A450P2 plasma screen problem

5. Adjustment Procedures
- Channel ▲ ▼ Key: Select an item.
- Volume ◀▶ Key: Adjust the value up or down.
- MENU Key: Save the changes to the EEPROM and return to the higher-level mode.
- Using the Numeric (0~9) keys, you can select a channel.
- Using the SOURCE key, you can switch AV modes.

[vinceroger69]

Re: Samsung PS42A450P2 plasma screen problem

soz did not see that it was a chinese thing toms instructions should be the one
Press info, menu, mute, power on the remote, but as you cant see what to press as your picture is bad (just looked at your pic in post 2 ) not sure what to suggest

[mrbigsteel]

Re: Samsung PS42A450P2 plasma screen problem

Pressing "Source 2 5 8 0" while the TV is displaying corrupted HDMI input does not work. That code must be particular to Tw2005's Chinese TV, not this Samsung.

I wish I knew somebody with the same model TV. They would be able to get into the factory menu (using Info Menu Mute Power) and write down what keystroke sequence would reset the TV to factory settings. I could try repeating them blind on my TV.

[mrbigsteel]

Re: Samsung PS42A450P2 plasma screen problem

I learned how to perform a factory reset while the TV is on:

Press and hold "Exit" for about 10-12 seconds. The factory reset menu (see attached picture) will appear. Press the left arrow to select the "OK" button. Then press "Enter". The TV will reset and turn off in a second or two. When you turn the TV back on, you will have to go through the normal TV setup procedure as if you just bought the TV. Also, the "Panel On Time" counter resets to 0 hours.

Unfortunately, the factory reset did not solve my display problem.

Cadiman, I also tried your suggestion to press the surface mount capacitors on the Main Board to see if this might improve the picture. It didn't.

Sigh. I guess a Main Board replacement is the next step, if I can find one.

[mrbigsteel]

Re: Samsung PS42A450P2 plasma screen problem

My main board is model BN94-01671D. It doesn't appear to be available in the USA. Not a big surprise since I bought the TV when I lived in Europe. (Didn't have time to sell it before I came back to the States.)

SuppliesNow.nl sell it for EUR 143 + freight. Seems high given the price of a new 42-inch plasma TV today.

Do you guys from the UK have any suggested parts sources?

Or, does anybody know if there is an equivalent USA model that has component jacks and an NTSC decoder instead of these SCART jacks and a PAL decoder? Would a picture of the board help?