Samsung PN50B450B1D no picture

[jason424]

A contact who had a pile of TV's that weren't working was asking me to work on this one for him.

The TV turns on (chimes and Ctrl board LED blink every 5 sec.) but no picture. He had already replaced the Ctrl board and I'm checking with him on the orig part # to be sure he replaced with the exact same board. The VA and VS voltage on the panel sticker say 55 and 209 respectively. When I test the points on the Power Board I get 0.00 and 6.3 for the VA and VS voltages (DC).
In doing some research it seems that the Y main is typically an issue on these sets. But I worry since I don't get the correct voltage for both the VA and VS that it may be a further issue?

[Hamie]

Re: Samsung PN50B450B1D no picture

So you get no vs and va with the y-sus unplugged?

These may only appear for a few seconds when turning on the tv. So you need to test them quick.

[jason424]

Re: Samsung PN50B450B1D no picture

So you get no vs and va with the y-sus unplugged?

These may only appear for a few seconds when turning on the tv. So you need to test them quick.

This is with everything plugged in and the power button pressed ON. Nothing is unplugged.

[Hamie]

Re: Samsung PN50B450B1D no picture

Well you need to see if they come up with the ysus disconnected.

Also see if the mainboard sends the vs-on signal.

[jason424]

Re: Samsung PN50B450B1D no picture

With the cable from the power board to the ysus unplugged I still get 0.00 and 6.3 (then drains down towards 0).

I get nothing at the VS_ON, while i do have 5v and .1 at the PS_ON

[Hamie]

Re: Samsung PN50B450B1D no picture

OK so jumps the power supply on without the mainboard.

Ps-on to Gnd.
Vs-on to stby.

[jason424]

Re: Samsung PN50B450B1D no picture

OK so jumps the power supply on without the mainboard.

Ps-on to Gnd.
Vs-on to stby.

To clarify, plug the ysus board back in and unplug the cable to the main board and use those pins on the power board connector to jump?

[Hamie]

Re: Samsung PN50B450B1D no picture

Yes, from your description your mainboard isn't sending the signal vs-on.

The mainboard sends both ps-on and vs-on signals.

Ps-on goes low (so you ground it)
Vs-on goes high (standby will do as it will be around 5v)

You can leave the y disconnected if you want, the purpose of this is purely to see if vs and va will come up.

[jason424]

Re: Samsung PN50B450B1D no picture

Does it matter which ground? Looks like there are many, with diff voltages after

[maxvalutech]

Re: Samsung PN50B450B1D no picture

No it doesn't matter - the other ref is to say to what part of the circuit that particular ground point is attached. Once Hamie gets the info on this he can then get to the nitty gritty of your sets problem

[jason424]

Re: Samsung PN50B450B1D no picture

Va went to 117.2
Vs quick flashed a 37 then must have went higher than the 200 my meter was set to. Tried again and got 12X then went too high again. So it seems that those jumpers did make them go up as you assumed.

[jason424]

Re: Samsung PN50B450B1D no picture

I should also add that I found the new board that was replaced is NOT the same number as the original. The original board was FL 700B and the new one that was put in is FL 705D. I'm not sure how that will fit in to the equation of issues. He still has the board but since he is not local, will be a bit before I can get that back in if needed.

[Hamie]

Re: Samsung PN50B450B1D no picture

So you have a faulty power supply.

Previously when you said vs-on from the mainboard was 0. as you press the power button the does the vs-on spike then go back to 0. If so your main board is probably OK.

[jason424]

Re: Samsung PN50B450B1D no picture

Keep the jumpers on to test the VS_ON scenario?

[Hamie]

Re: Samsung PN50B450B1D no picture

No remove them and plug everything back in.

[jason424]

Re: Samsung PN50B450B1D no picture

OK will do. Thank you for all of your help, I appreciate it!

[jason424]

Re: Samsung PN50B450B1D no picture

Ok so I stuck my red probe in the VS-on (top right hole in first pic) and black to chassis and get no change when powering on the set. I also put the red on top pin on the main board (pic two) where the opposite end of the cable plugs into the main board and get no change there as well.

[Hamie]

Re: Samsung PN50B450B1D no picture

Edit wrong

[Hamie]

Re: Samsung PN50B450B1D no picture

Upload photo of the other table that connects to ctrl board

[jason424]

Re: Samsung PN50B450B1D no picture

I'm not sure which cable(?) u wanted a pic of