Samsung S42AX-YB07 Plasma No Picture

[JontyUK]

Hi,
This TV has no picture, menu not present etc but sound ok re start up tune.
Relays pull in and all voltages present at the test points & cable connectors.
Green pulse led blinking every one second - seems ok
Original Y Board has been completely replaced due to blown components. LJ41 05779A.
Y Buffer board tested with no shorts found.
No apparent change on screen re glow on start up.
Changed Logic Control board LJ41-06335A but no change.

On TV all voltages checked at each TP:
VS 207v
Va 54v
Vsc -192
All above ok

However, on new board Ve is 94v - TV states it should be 0v.
On original card it was 0v.

I've spent the day going through this forum and have learnt a lot already but I cannot find how to adjust Ve.
There does not appear to be a variable pot VR-Ve on this TV?

Any help is appreciated.

[Unspun01]

Re: Samsung S42AX-YB07 Plasma No Picture

You have provided the part number of the plasma panel, but what is the actual model number of your TV? I have seen part number LJ41-05779A before in a Samsung 42B430 and 42B450 models.

The startup sound is normal but not helpful here. Please explain if you get audio from the connected device (DVD, cable, etc). If you have voices and sounds but no picture then your mainboard is probably ok.

When you say you have no picture, does the panel prime with raster at all (like does it light up in a dark room, even if there is no image??). Or is the panel completely dead with no image at all... Like completely black in dark room. Or does image come up but very dark and grainy like dark static and cannot make out any details?

Ve seems high. I agree it should be 0V as per attached photo of panel sticker.

[JontyUK]

Re: Samsung S42AX-YB07 Plasma No Picture

Thanks for your reply.

I cannot see any raster, even in a darkened room when it starts up.

Have not tried connecting dvd to same - will do and feed back.

Attached Panel label, scope output, Chn 1 on Z Board, Chn 2 on Y sus.

No idea how to change Ve to 0V ? Cannot see a point anywhere.




Thanks again,

[JontyUK]

Re: Samsung S42AX-YB07 Plasma No Picture

Both scope probes are on x10.

[JontyUK]

Re: Samsung S42AX-YB07 Plasma No Picture

From scart, DVD sound is ok

[Unspun01]

Re: Samsung S42AX-YB07 Plasma No Picture

Samsung has a method to perform panel self test, but it's only helpful to rule out the mainboard, and only available if the panel voltages and Y-Main, X-Main are working to confirm basic panel tests.

If you have sound through speakers with DVD playing, then I think your mainboard is turning on OK.

If you do not get any panel priming, even in a dark room, then your Y-Main or X-Main may not be working correctly.

I do not know why you have such a high Ve. Ve is derived on Y-Main and not adjustable as far as I know. Where are you testing Ve? There is a "labeled" test point near upper right corner of Y-Main board.

Can you please upload photos of the entire rear of the TV, including closeups of each board as they are installed and connected?

You said Y-Main board is replaced, but common issue on X-Main also is shorted IGBTs. You might want to check fuses on both Y-Main and X-Main and re-check for shorted components (specifically anything attached to a heatsink).

[JontyUK]

Re: Samsung S42AX-YB07 Plasma No Picture

Thank you for the advice.

Ve was tested from the Ve test point as you noted.

I have checked this voltage before some time ago and it was 0v.

I will check at component level again and get photos - feedback hopefully Monday.

Thanks for your help.

[LabRat101]

Re: Samsung S42AX-YB07 Plasma No Picture

Thanks for your reply.

I cannot see any raster, even in a darkened room when it starts up.

Have not tried connecting dvd to same - will do and feed back.

Attached Panel label, scope output, Chn 1 on Z Board, Chn 2 on Y sus.

No idea how to change Ve to 0V ? Cannot see a point anywhere.
[ATTACH]192293[/ATTACH]

[ATTACH]192294[/ATTACH]

Thanks again,

The Stick is wrong I have the exact tv model the VE should be 91 volts
its written as 0 because its preset .
my label shows vs 54 .. vsc -198 ... vs 207 .. ve 91..
the check point is hidden just under the cap near the plug to x-main.

I have the exact problem as you have both the IGBT power blown and also the pushpull driver smd transistors marked as uy & wy I am going to replace them with general purpose npn & pnp as per Texas inst. 2n2222 and its partner 2n.....
The 10k on the gate is also bad . and properly the irs218.. driver chip.
sorry could not remember all the numbers.
I pull my plasma from the dumpster . after fixing the power supply it worked great for 15 minutes .. and the the Y-main blew .. can't find the cause of the failure . so i'v stripped it down to bare board and go though it bit by bit .

Looking for the complete circuit diag . got the lj41-05779a drawing only.
If you have an luck please post . Iv got a feeling its the irs218/9 chips .

DO not change the VE voltage its good 91 v my one is also shows 94 it depends on the version . The '0' is printed faint only bold apply.
The manual from Samsung shows it also as VE 91v