Samsung PN43D440A5D No backlight/Video

[crdz66]

Hello Fellas.
I need you opinion on this problem.

My plasma Tv turn on normaly but can't get backlight and video.
The voltage va, vs are too low in my opinion and according to panel specs.

I know (from some Samsung service manual) that as soon the tv turn on, this generate a va voltage enough for generate vs_on signal on control board and of course generate vs voltage for y,x main boards.

I check the va voltage on power supply board on the point called vatp that I supposed is va test point. (value on this point 9-11v only)

I include a picture from my power supply board (looks under transformer is, looks burn)

How can I check the transformer?
Do you think my problem (generate enough voltage) coming for defective transformer.

Thanks like always

[tom66]

Re: Samsung PN43D440A5D No backlight/Video

What do you see on Vs TP?

Transformer failures are very rare.

More likely on this model is failed X-main or Y-main board, which is shorted causing voltages to be low.

[crdz66]

Re: Samsung PN43D440A5D No backlight/Video

Vs Voltage same like 9-11volts

[crdz66]

Re: Samsung PN43D440A5D No backlight/Video

Sorry I forget include the picture

[tom66]

Re: Samsung PN43D440A5D No backlight/Video

I recommend unplugging the X-main and Y-main boards. These are the large brown left and right boards that drive the plasma display. Then see if Vs/Va rise to specified values on panel sticker.

[crdz66]

Re: Samsung PN43D440A5D No backlight/Video

Hello tom66

Still y and x board are disconnect the voltage on test point va give me 28v and dropped until 9.5v quickly. (tested on power supply board)

[tom66]

Re: Samsung PN43D440A5D No backlight/Video

What about Vs? The Vs is the most important voltage.

[crdz66]

Re: Samsung PN43D440A5D No backlight/Video

is same, vs have low voltage too.

[tom66]

Re: Samsung PN43D440A5D No backlight/Video

Can you check VSON on the connector going between power board and control board (this is not the same as the main board which has video inputs on it.)

[crdz66]

Re: Samsung PN43D440A5D No backlight/Video

As soon turn on the tv going 7v and dropped quickly .9mv

[tom66]

Re: Samsung PN43D440A5D No backlight/Video

7V is not right for that pin. Are you sure? Meter on VDC or VAC?

[crdz66]

Re: Samsung PN43D440A5D No backlight/Video

Use vdc

[mytomr]

Re: Samsung PN43D440A5D No backlight/Video

Most psu for plasma tv has its own logic controller on psu board itself, it receives logic hi/lo from main mcu on main board, then outputs logic hi/lo use for switching the Vs,Va and other sub-circuit within the psu board. Now, check the must haves of this logic controller ic (e.g.,, x'tal in/out for osc, reset, Vcc, gnd, input and outputs) or consult datasheet may help.