Samsung Plasma PN50C550G1F : no image, but sound is ok

[tom66]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Y-main = Y-sustain

VSCAN and VS are different. VSCAN and VSC are the same.

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Ok, everything connected as it is now, check VSCAN voltage on Y-main board.

Is Y-Main board is the same as Y sustain board?

Is VSCAN the same as VS? or is is some sort of "flat" testpoint on the Y-sustain board written VSC beside it ?

Right now, the y-sustain board isn't connected to the power supply (cable CN804 is disconnected). Do I need to connect the CN804 cable to power up the Y sustain board?

[tom66]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Ok, everything connected as it is now, check VSCAN voltage on Y-main board.

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

At this point, connect the control board back to the power board, and check if the voltages appear, then go away.

if I reconnect the logic board, I'm back to this setup:

Disconnect the CN804 that is connected to the Y-Sustain board.
Leave the CN802 connected to the logic board.
Leave the CN801 connected to the main A/V board.

Then the DC voltages on test point of power supply starts at:
212 VDC for Vs
55 VDC for Va
But immediately starts to ramp down to 0 VDC

The logic board LED do its pattern 5 seconds on, 2 seconds OFF

[tom66]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

At this point, connect the control board back to the power board, and check if the voltages appear, then go away.

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Ok I have try the following:

Disconnect the CN804 that is connected to the Y-Sustain board.
Disconnect the CN802 that is connected to the logic board.
Leave the CN801 connected to the main A/V board.

Add 1K resistors on CN802 connector:
- pull down on PS-ON
- pull up on VS-ON

The DC voltages on test point of power supply are steady at:
212 VDC for Vs
55 VDC for Va
Which is what the label says

So I guess the the power supply is fine.

What would be the next step?
troobleshoot/check the Y-Sustain, Y-Buffer, Logic ???

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

There's one thick cable going between main A/V board and power board, disconnect that and jumper anything required on there. Disconnect the connector between the control board (also called logic board, small green board usually below power board) and power board too.

All right, just to recap...

DISCONECT ALL 3 CABLES
I disconnect the CN804 that is connected to the Y-Sustain board.
I disconnect the CN802 that is connected to the logic board.
I disconnect the CN801 that is connected to the main A/V board.

JUMPERS:
Install the jumper on the CN801 cable?

i'm asking, because in your post, you're talking about the cable connected to the main A/V board (CN801) and that cable is wider/larger than the CN802, but tinner... Also, that connector only has PS-0N that seems relevant.

The CN802 on the other hand has both PS-ON and VS-ON, and in previous posts, MagicSmoke told me to drive them to activate the PowerSupply and the Vs DC line ...

Jay

[tom66]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

There's one thick cable going between main A/V board and power board, disconnect that and jumper anything required on there. Disconnect the connector between the control board (also called logic board, small green board usually below power board) and power board too.

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

PS-ON needs to go LOW (active LOW), VS-ON goes HIGH (active HIGH) this will turn on low voltages and high voltages (~200V, ~60V Vs/Va)

This is for Samsung, it is different for other brands, most use active HIGH for both PS-ON and VS-ON.

All right,

So for the connector CN802
- PS-ON : pull down (gnd using 1K resistor)
- VS-ON : pull up (high 5.3V using 1k resistor)

For the connector CN801, there is also a PS-ON.
Do I use a pull down also for that pin, or should I simply left the cable connected to the main board?

Regards.

[tom66]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

PS-ON needs to go LOW (active LOW), VS-ON goes HIGH (active HIGH) this will turn on low voltages and high voltages (~200V, ~60V Vs/Va)

This is for Samsung, it is different for other brands, most use active HIGH for both PS-ON and VS-ON.

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

So basically, I disconnect all connectors from the power supply and short (using the resistor) the specified pin to activate the power supply.
Then I should be able to verify the different output voltages to see if they are at their expected levels?

Do I need to leave the CN801 cable connected to power on the tv?
If I don't, I can't turn the TV on ... Do I need to also drive the PS-ON of the CN801 cconnector?

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

The resistor is for jumping the PS-on signal to 5vstby to power on, not for a load. You can use wire but it makes the VS volts read high.

Main board connector disconnected, this is where the resistor will go. Most Samsung psu's jump ps-on to 5.3v stby to force on. It actually only needs > 2.5v that's why the resistor is needed. Some also have a VS-on that needs a jumper also.

According to pic here http://assets.shopjimmy.com/media/ca...330a-top_1.jpg

You need to jumper CN802 pins 1 & 2 with Pins 5 & 6 w/ 1k resistors to fully power up psu. No connections to other boards.

Then check for 15v on CN801 and VS & VA volts at their test points.

Ah ok, so it's like a PC power suppy, where you ground a wire to let it fire up...

Sorry, i misunderstood the instruction in the first place...

So basically, I disconnect all connectors from the power supply and short (using the resistor) the specified pin to activate the power supply.
Then I should be able to verify the different output voltages to see if they are at their expected levels?

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

5-2 can be PSU but check Vs/Va and if that is low/bad then that may be an issue.
In protect mode, it should become briefly available then go away.

When I power ON the TV, the voltage seems to start at their nominal DC voltage, but rapidly drop to 0VDC in about 10-20 seconds.

I.E,
Vs starts at about 200VDC and drops to 0VDC in a few seconds.
Va starts at about 50VDC and drops to 0VDC in a few seconds.

That seems to be what you are describing?

So this would indicate the power supply is healty and the problem would be elsewhere?

Jay

[MagicSmoke]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

The resistor is for jumping the PS-on signal to 5vstby to power on, not for a load. You can use wire but it makes the VS volts read high.

Main board connector disconnected, this is where the resistor will go. Most Samsung psu's jump ps-on to 5.3v stby to force on. It actually only needs > 2.5v that's why the resistor is needed. Some also have a VS-on that needs a jumper also.

According to pic here http://assets.shopjimmy.com/media/ca...330a-top_1.jpg

You need to jumper CN802 pins 1 & 2 with Pins 5 & 6 w/ 1k resistors to fully power up psu. No connections to other boards.

Then check for 15v on CN801 and VS & VA volts at their test points.

[tom66]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

5-2 can be PSU but check Vs/Va and if that is low/bad then that may be an issue.
In protect mode, it should become briefly available then go away.

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Also, the green led on the logic board blinks with the following pattern:

5 seconds ON
2 seconds OFF

Jay

Isn't that pattern for the TV protection mode?

If so is that exclude the psu from the list of culprit?

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Also, the green led on the logic board blinks with the following pattern:

5 seconds ON
2 seconds OFF

Jay

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

You can disconnect the cables that power the X & Y boards and force PSU on with a 1k ohm resistor to see if VA & VS volts are present and stable.

I've done the check with a 2K Ohms load (the 1K I have are only rated at 1/4W).

When all boards connected:
or
When I disconnect only X-board
or
When I disconnect both X-board and Y-sustain

I get the same behavior:
- Vs starts at 200+ VDC and go dow to 0V in a few seconds

When I disconnect only the logic board:
- Vs starts at 0VDC and ramp up to 10VDC

When I disconnect the main board (the ones with RCA and HDMI connectors), I can't power on the TV.


Note: X board is powered from Y-sustain cable, so I can't leave power to only X board without havin also the y-sustain connected)


???

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

I have gone thru a whole slew of checks on a similar TV...

https://www.badcaps.net/forum/showthread.php?t=42835

Some of the checks might help you...

Thanks, will read the thread as soon as I am done drinking my coffee

Jay

[Michale32086]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

I have gone thru a whole slew of checks on a similar TV...

https://www.badcaps.net/forum/showthread.php?t=42835

Some of the checks might help you...