Samsung PN42C430 Plasma no picture please HELP

[tom66]

Re: Samsung PN42C430 Plasma no picture please HELP

Sorry should have clarified. Volt meter on DC 20V and measure each pin. Red probe on the appropriate pin and black probe on the metal chassis of the TV. The TV should be in the fault state.

Check the pins marked VSON, PSON and the 5.2V/5.3V/5.4V/15V if present.

[sergio2013]

Re: Samsung PN42C430 Plasma no picture please HELP

Ok ill try that now

[sergio2013]

Re: Samsung PN42C430 Plasma no picture please HELP

Sorry should have clarified. Volt meter on DC 20V and measure each pin. Red probe on the appropriate pin and black probe on the metal chassis of the TV. The TV should be in the fault state.

Check the pins marked VSON, PSON and the 5.2V/5.3V/5.4V/15V if present.

cable that goes between the control board and power board

vson - 0.000 and sometimes goes to 0.001

pson - 0.057

5.3 volts - 5.221

5.3 volts - 5.221

the cable that goes from the ps to the main board where the hdmi connectors are measures

5.3 volts - 5.215

15 volts - 14.89

15 volts - 14.89

5.3 volts - 5.214

5.3 volts - 5.214

15 volts - 14.90

va on ps test point with fault supposed to be 54 and its 0.102
VS on ps test point with fault supposed to be 207 and its at 5.349
vsc on y-main test point is supposed to be -197 and with fault its -0.017

With out fault the VA, VS and VSC is in spec.

[tom66]

Re: Samsung PN42C430 Plasma no picture please HELP

OK, and when the fault isn't present can you check VSON again?

[sergio2013]

Re: Samsung PN42C430 Plasma no picture please HELP

OK, and when the fault isn't present can you check VSON again?

Yeah I did that also and I think I remember it had a reading of 3. something, but it was a 3 digit number like 3.555.

[tom66]

Re: Samsung PN42C430 Plasma no picture please HELP

OK, so this means the control board is keeping the power supply on (VSON LOW means power is on) but the power supply is not able to keep itself on. So next step is to try the tapping trick that Alastair suggested -- try tapping along the heatsinks and use an insulated screwdriver. Don't tap the metal back panel itself.

[sergio2013]

Re: Samsung PN42C430 Plasma no picture please HELP

OK, so this means the control board is keeping the power supply on (VSON LOW means power is on) but the power supply is not able to keep itself on. So next step is to try the tapping trick that Alastair suggested -- try tapping along the heatsinks and use an insulated screwdriver. Don't tap the metal back panel itself.

I tried that already as well when he suggested it when it had the fault I even put force on the center of the boards and made them flex and it didn't change anything

[tom66]

Re: Samsung PN42C430 Plasma no picture please HELP

If you want an "easy" solution I would just replace the PSU board -- it's available for under £30 on eBay here (probably less in US) -- though I'm still convinced you can repair it.

[sergio2013]

Re: Samsung PN42C430 Plasma no picture please HELP

If you want an "easy" solution I would just replace the PSU board -- it's available for under £30 on eBay here (probably less in US) -- though I'm still convinced you can repair it.

You really think it could be that? I'm leaning toward the Y-Main board because after testing all the voltages you asked me to test I turned the set off and back on and the screen came on but with lots of dots as I described earlier that happened once before, I tried unplugging and plugging back in with same result this time the dots would not go away, but screen is on, so with the screen on with all the dots I tested the Va and VS on the power supply test points and they were on spec, then I tested the VSCAN test point on the Y-Main and it was way lower than what its supposed to be, its supposed to be -197 that's what the panel says and it was at -156, so then I adjusted the VSCAN POD to see if I could get it to go higher and with the pod all the way to the left I got it to -170 still way under spec, but at least it made all the dots go away, left it on for 10 min and screen went black again and sound continued, so then I turned it off and back on and the screen came on again with no dots, so I decided to remove the Y-Buffer and just leave the Y-Main connected and everything else connected as well then the TV would just click on and off, it would not power up, so then I disconnected the Y-Main and turned the set on and it came on just with sound and no picture.

[tom66]

Re: Samsung PN42C430 Plasma no picture please HELP

I'm not confident it is the Y-main because it wouldn't normally cause Vs to collapse. I'm trying to think of a way to test it though and I'm coming up blank. The problem is the Y-main draws the most power and the X-main draws much less without the Y-main connected. So unplugging it isn't a valid test. In order to cause the failure, the Y-main would have to have an occasional, random short circuit (which would be very rare), but the power board could have any number of intermittent components.

[sergio2013]

Re: Samsung PN42C430 Plasma no picture please HELP

I'm not confident it is the Y-main because it wouldn't normally cause Vs to collapse. I'm trying to think of a way to test it though and I'm coming up blank. The problem is the Y-main draws the most power and the X-main draws much less without the Y-main connected. So unplugging it isn't a valid test. In order to cause the failure, the Y-main would have to have an occasional, random short circuit (which would be very rare), but the power board could have any number of intermittent components.

Well when I put the Y-Main back in now the set will no longer power up, take it out and the set powers up, this only started happening after I powered up the set with the Y-Main connected but not the Y-Buffer connected

[sergio2013]

Re: Samsung PN42C430 Plasma no picture please HELP

Could it be that I ruined the Y-Main just by leaving it connected with out the Y-buffer connected to it? cause now when I put everything back together it wont power up it just clicks and if I take out the Y-Main it powers on, just no picture because the Y-Main is disconnected.

[tom66]

Re: Samsung PN42C430 Plasma no picture please HELP

Perhaps you did have an intermittent failure on your Y-main and it has become permanent. I had the same issue with an X-main. It wasn't working right (poor picture), I took it out to check for faults, put it back in and the set wouldn't power up with it plugged in. When unplugged it worked fine.

One way to test this would be to do some ohm checks between VS and GND on the Y-main.

And no, unplugging the buffer does not damage the Y-main as long as all connectors were removed before it was powered up.

[sergio2013]

Re: Samsung PN42C430 Plasma no picture please HELP

Perhaps you did have an intermittent failure on your Y-main and it has become permanent. I had the same issue with an X-main. It wasn't working right (poor picture), I took it out to check for faults, put it back in and the set wouldn't power up with it plugged in. When unplugged it worked fine.

One way to test this would be to do some ohm checks between VS and GND on the Y-main.

And no, unplugging the buffer does not damage the Y-main as long as all connectors were removed before it was powered up.

Yes the set was off when I disconnected and re-connected the boards I even discharge the caps by holding the power button down and pressing it repeatedly after unplugging the set from the wall outlet. Do I do these ohm checks with the board out of the set? what should it read?

[sergio2013]

Re: Samsung PN42C430 Plasma no picture please HELP

I did it with it out of the set don't know if that's right, but it reads 1.200 and just keeps dropping really fast, like if the power is discharging from the capacitors or something.

[tom66]

Re: Samsung PN42C430 Plasma no picture please HELP

On what range was that measured?

[sergio2013]

Re: Samsung PN42C430 Plasma no picture please HELP

On what range was that measured?

My multimeter is a fluke 177 true rms auto range. I had it on auto range when I did the measurements.

[tom66]

Re: Samsung PN42C430 Plasma no picture please HELP

Set it on ohms then tell us if it is Kohm, Mohm or ohm.

[sergio2013]

Re: Samsung PN42C430 Plasma no picture please HELP

Set it on ohms then tell us if it is Kohm, Mohm or ohm.

Its Mohm

[tom66]

Re: Samsung PN42C430 Plasma no picture please HELP

There's no short directly then, but also test between VS and ERC, and ERC and GND. The ERC is on the connector which goes to the X-main.