Samsung PS42A416C1D No Picture

[dick_barton]

Hello,
I have picked up a Samsung Plasma set with sound but no picture. At switch on in a darken room the screen does not appear to prime.

I've taken a few readings and will post some photo's tomorrow.

Panel Label Voltages
VS 205V, Va 54V, Vsc -190V, Ve 95V


Board readings
VS 205V
Va 54V
VSCH 50V to 57V fluctuating
Vscan -99mV
Vg = 14.9V
13V_Amp = 12.8V
D5.3V = 5.33V
PFC = 402V
VCC = 15V



CN807 connector
STD5V = NC
VS_On = 3.3V (0V at STBY)
NC
PS_On = 0.48V (3.35V at STBY)
RTN = NC
D5.3V = NC
RTN
RTN
D5.3V = 5.33V
D5.3V = 5.33V


CN809 connector
1. Vs = 205V
2. Vs = 205V
3. RTN = 0V
4. RTN = 0V
5. Vg =14.9V

I can see the potentiometer for adjusting Ve on the X-Main board but not the test point. Also is Vscan = Vsc.
Thanks

Edit.
Led on the logic board flashes constantly at 0.5 sec On, 0.5 sec Off.

[ReeceyBurger123]

Re: Samsung PS42A416C1D No Picture

Vscan is Vsc yes, also Ve will be on the traces near where it says Ve.

[ReeceyBurger123]

Re: Samsung PS42A416C1D No Picture

I would suggest unplugging the buffers and retesting as if Vsc is variating like that it means its trying to start but the controller is it shutting down. If it stays the same you probably just have some shorted fets on the Ymain which is nothing uncommon for this chassis.

[dick_barton]

Re: Samsung PS42A416C1D No Picture

Thanks for the pointer. Appreciated. Just for me to be clear, do you mean disconnect the Y buffer board completely from the Y-Main and then give it a try?

[ReeceyBurger123]

Re: Samsung PS42A416C1D No Picture

Yes completely unplug the Ybuffer and retest Vs buddy.

[dick_barton]

Re: Samsung PS42A416C1D No Picture

Hello ReeceyBurger123,
With the Y buffers removed completely Vscan = -91mV. So it doesn't look like the buffers are loading it down. Next step will be to remove the Y-Main and start fault finding.
Thanks

[ReeceyBurger123]

Re: Samsung PS42A416C1D No Picture

Yeah seems like a Ymain issue to me, these Tv's I dont think use combined ERC so the Ymain cannot damage the Xmain.

[Kjelds]

Re: Samsung PS42A416C1D No Picture

Had the same issue on my Samsung plasma after a capacitor blew up and several other components also died. Replaced the Y-sus/Y-main for around £30 with shipping and now it seems to work again.

[dick_barton]

Re: Samsung PS42A416C1D No Picture

Pictures of set for future reference. Fault finding needs to be done on the Y-Main,. The Y buffer board has not been reconnected since last test.

[ReeceyBurger123]

Re: Samsung PS42A416C1D No Picture

DB after you have diagnosed the Ymain you need to also recap the powersupply. The Samwha Wl and Wb caps on that supply have a habit of failing and if they do the set wont switch on again. So my advise is replace all the known bad caps on the Psu after the Ymain repair

[flocko]

Re: Samsung PS42A416C1D No Picture

From my little black book of Samsung repairs. I list R5032/C5030/D5014 + U5015 as suspect faulty components for the LJ92-01483A Y Sus. not seen one in years.hope this is of help.could have one kicking about in my old stock

[dick_barton]

Re: Samsung PS42A416C1D No Picture

From my little black book of Samsung repairs. I list R5032/C5030/D5014 + U5015 as suspect faulty components for the LJ92-01483A Y Sus. not seen one in years.hope this is of help.could have one kicking about in my old stock

Hello Flocko, ReeceyBurger123,
Thanks for your useful tips which may well have identified the problem. D5014 (UF4007) is short circuit so I'll test the other components you mention. None of the Fets appear to have blown or are short circuit so hopefully not a major build.
Will replace the caps in the power supply as suggested.

[flocko]

Re: Samsung PS42A416C1D No Picture

You also need to test all the little green fuses that are scattered about the board,as I recall the components mounted on the heat-sinks were not a problem on this board,just the IC and the few other parts that I listed, but as I say it has been a long time since one of these has come my way.

[dick_barton]

Re: Samsung PS42A416C1D No Picture

Hello Flocko,
C5030 (100uF 35V) tests out of circuit both ESR & value are OK but will replace it anyway.

R5032 I cannot for the life of me locate at the moment. There is a C5032 which is an smd cap connected to pin 2 of U5015 (A6252).

There are no unaccounted low resistances between U5015 pins to ground. However since I will have to order some parts I may as well also replace it.

I did notice that this set has a large number of different types of fuses on board which I have checked out, all OK, but another check would not hurt.

[flocko]

Re: Samsung PS42A416C1D No Picture

The resistor is through hole mounted not SMD as I recall,the PWM switching regulator I would replace

[dick_barton]

Re: Samsung PS42A416C1D No Picture

The resistor is through hole mounted not SMD as I recall,the PWM switching regulator I would replace

Thanks once again Flocko,
The capacitor is an smd connected to Pin 2 of U5015 and the stand up resistor is R5037 and is connected to Pin 2 of U5015. R5045 is also a stand up resistor and is connected to pin 3 of U5015. I'll just check them all out.

[flocko]

Re: Samsung PS42A416C1D No Picture

Thats me misreading my own notes.when i checked my little black book it is R 5037 and C 5030 not the SMD cap C 5032 sorry mate. I will be booking in with Specsavers tomorrow for an eye test

[dick_barton]

Re: Samsung PS42A416C1D No Picture

No worries. Got there in the end. Have ordered the parts. In the meantime I'll check the caps required to be replaced on the power supply and make sure I have sufficient replacements for a swapping out. Thanks once again.

[ReeceyBurger123]

Re: Samsung PS42A416C1D No Picture

Nice work keep us updated DB

[dick_barton]

Re: Samsung PS42A416C1D No Picture

Parts arrived and fitted. Set up and running. Will leave it on soak for a while before closing it up.

Will order replacement capacitors for the power supply and fit before moving set on.

Thanks to Flocko and others for their invaluable help and expertise.