Samsung PS42A457P1D stuck in standby

[Ooger]

Morning all,

First post here after registering yesterday and reading loads of useful stuff, some of which I didn't really understand too much of, but its a good start.

I think I need your expert help though.

I've got a problem with a Samsung PS42A457 plasma which is permanenently stuck in standby. The light is on and it receives the IR commands from the remote, but it wont come out of standby.

I've read that this is likely to be a problem with the caps, so off the back came, expecting to see some blown/bubbled/leaking capacitors.

Sadly none found. Well. I think none found. Plenty of dust and fluff though.

Theres one black capacitor which looks a bit suspicious on the power board. Its got a small black dot on the top, but it still looks sealed. The dot looks like marker pen though, to the untrained eye (mine).

I've attached a photo. Can anyone give me an opinion please before I start taking the board off and removing/replacing anything?

The caps are all made by SAMWHA and none of them seem blown, unevenly seated or leaking, apart from this one. Ive read here that "generally" theyre quite reliable - compared to some.

Oddly, theres the burn-in test records close to this cap, and they're marked on the circuitboard with what looks like the same "pen"....helpful, not. Just makes me a bit sceptical of what I'm looking for.

I've got a multimeter and know my way around basic electronics, but thats about it, so far.....happy to try anything though, with your patience.


Thanks for reading.

[smai]

is there no power button on the TV itself? when you push it does it feel like its "clicking"

will you upload a picture of the whole back side, i believe there is a test mode for samy plasmas procedures i think are in the stickys posted my tom66

[mmartell]

That mark on the top of the capacitor is there from the factory. FWIW it doesn't look bloated to me however caps can look ok and fail an ESR test.

Need more pics, one of the whole back of the set and pics of each board separately.

[Alastair E]

That 22uF cap is the supply start-up cap for the Stdby 5V supply. (small DIL-7pin chip by its side....
Guessing its working--as its in Standby with the red-led showing....

Does header on PSU --'PS-On' have a voltage on it?

Does 'Vs-On' have any voltage on it?

Normal running--the Ps-on will be '0' V and Vs-on will be around 3V

Ps-on will be 3.4V in Standby.

[Ooger]

Thanks everyone for replies so far, just caught up.

I've got a photo of the rear of the set, all boards attached.

I'm not at home at the moment so can't test anything else right now.

The power button on the front is one of those touch sensitive ones - its not a button as such. Pressing it does nothing, but the light remains on.

Theres no "clicking" coming from anywhere apart from the large transformer on the SMPS (black square, between the 3rd and 4th heatsinks). Its a very quiet clicking though (more like a tick), and couldnt be heard with the back on...

I feared the black mark was just that....a black mark

More to follow when I get home. I might need some advice testing voltages please - just the points to test, I can use a multimeter.

*EDIT - picture taken with X and Y boards disconnected - there are loose ribbon cables just hanging, I know this*

[tom66]

Does faint ticking persist with the X- and Y-main unplugged?

[Ooger]

Yes the ticking persists without the X and Y boards

I'm going to check the voltage and any change in voltage tonight when the power button is pressed whilst it is in standby

Hopefully this is a good start, as well as the answers to the q's above.

[Ooger]

Considering options here, and as a preemptive thought (I know, goes against the "fix it" grain) , is this a straight swap:

http://www.ebay.co.uk/itm/Samsung-PS...item3cdaf12f0e

I can see its not identical - but its because the ebay listing is a revision 1.01, and my SMPS is 1.1

Just out of interest - what are the differences?

Obviously a swap of the whole board just means my defective board may be replaced by one that is about to become defective, for the same reasons.....

[Ooger]

Originally Posted by Alastair E

That 22uF cap is the supply start-up cap for the Stdby 5V supply. (small DIL-7pin chip by its side....
Guessing its working--as its in Standby with the red-led showing....

Does header on PSU --'PS-On' have a voltage on it?

Does 'Vs-On' have any voltage on it?

Normal running--the Ps-on will be '0' V and Vs-on will be around 3V

Ps-on will be 3.4V in Standby.

In standby,

- PS-ON on the SMPS gives me 3.2V - measured from pin 1 on CN801. It fluctuates from 3.2 to 3.4.

- Vs-ON reads 0V - nothing at all at pin

- Hitting the power switch whilst measuring these does not affect the readings, they stay the same.

[Ooger]

For completeness if anyone comes back to this thread, I replaced 6 capacitors on the PSU board with uprated ones, and voila.

Fixed.

The irregular ticking was replaced with a gentle humm before it fired up.

Another case where the caps didnt look bad, but were.
Next please!

[Zerocool5050]

Any photos of after you replaced them and whitch ones you did as I have very much the same problem.

[satinser]

Just come across this thread and noticed that the last question remained not answered. Just thought i would end this thread with information that might aid future reference to stuck in standby with this power supply. Had a number like this with standby led showing but with no response. If looking carefully at standby illumination it can be seen to be slightly pulsing and is invariably caused by complete degradation of CB801 (22uf 450volt). Had a number of these lately that have degraded so badly that lost their capacitance completely.
Hope this helps future reference to this thread.

[tom66]

Interesting that the 450V cap goes.

My iiyama LCD monitor was killed when the 450V cap failed on the primary. Popped the primary-side flyback transistor.

Replaced transistor, resistor and cap and all was well, but thought that the failure of it was an isolated incident - obviously not.

[RepairSak]

Having exactly the same problem.
Thank you very much "satinser" for giving details, I'll try checking-replacing the 22μF/450V cap.
Dear "Ooger" if possible, answer the question which 6 caps you replaced. Maybe you replaced more than the ones needed.

[RepairSak]

Indeed CB801 22μF/450V was the problem. Replaced it and all fine. Also replaced the 50V caps around the STDBY area just in case. TV repaired!!

[tvtimmy]

Good job!